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M12M GPS Receiver User's Guide

1. Self clinching M3 0 female standoffs available in lengths from 5 to 25 mm 4 2mm round i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions System Integration The M12M receiver is an intelligent GPS sensor intended to be used as a component ina precision positioning navigation or timing system The M12M is capable of providing autonomous position velocity and time information over a standard serial port The minimum usable system combines the M12M receiver antenna and an intelligent system controller device Interface Protocols The M12M receiver has either one M12M Timing Receiver or two M12M Positioning Receiver serial data ports The first port provides the main control and data path between the M12M and the system controller The second port on the M12M positioning receiver is dedicated to RTCM DGPS correction inputs to the receiver Refer to table below for the interface protocol parameters Table 3 6 M12M Oncore Interface Protocols Format Binary NMEA 0183 RTCM SC 104 Type 1 or 9 Type Binary ASCII nee Direction In Out In Out In Port 1 1 2 Baud Rate 9600 4800 2400 4800 9600 Parity None None None Data Bits 8 8 8 Start Stop bits 1 1 1 1 1 1 Serial Input Output The serial interface pins RxD and TxD are the main signals available for user connection A ground connection is also required to complete the serial inte
2. ApPdxxxxxXxXxxXxXXxxxxxxC lt CR gt lt LF gt where d user datum ID XXXXXXXXXXXXXXXXX C 0x31 Message length 25 bytes 50 17 bytes all 0x00 Complete hex string to query current User Defined Datum Parameters 0x40 40 41 70 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 31 OD OA Change current User Defined Datum Parameters ApdsssffiiffffxxyyzzC lt CR gt lt LF gt where d datum ID sssff semi major axis m sss integer part ff fractional part iiffff inverse flattening ii integer part ffff fractional part xx delta X 0 1 m resolution yy delta Y 0 1 m resolution zz delta Z 0 1 m resolution C checksum Message length 25 bytes Response to either command 50 6 000 000 7 000 000 0 999 0 0 0 999 285 305 0 999 999 999 0 0 0 999999999 32 768 32 767 3276 8 3276 7 32 768 32 767 3276 8 3276 7 32 768 32 767 3276 8 3276 7 ApdsssffiiffffxxyyzzC lt CR gt lt LF gt where d datum ID sssff semi major axis m sss integer part ff fractional part iiffff inverse flattening 50 6 000 000 7 000 000 0 999 0 0 0 999 ii integer part 285 305 ffff fractional part xx delta X 0 1 m resolution yy delta Y 0 1 m resolution zz delta Z 0 1 m resolution C checksum Message length 25 bytes 0 999 999 999 0 0 0 999999999 32 768 32 767 3276 8 3276 7 32 768 32 767 3276 8 3276 7 32 768 32 767 3
3. ee e __________ 25 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Electromagnetic Considerations The Oncore receiver PC boards contain a very sensitive RF receiver therefore you must observe certain precautions to prevent possible interference from the host system Because the electromagnetic environment will vary for each OEM application it is not possible to define exact guidelines to assure electromagnetic compatibility The frequency of GPS is 1 575 GHz Frequencies or harmonics close to the GPS frequency may interfere with the operation of the receiver desensitizing the performance Symptoms include lower signal to noise values longer TTFFs and the inability to acquire and track signals In cases where RF interference is suspected common remedies are to provide the receiver with additional RF shielding and or moving the antenna away from the source of the interference RF Shielding The RF circuitry sections on the M12M are surrounded with an RF dam to provide some protection against potential interference from external sources When a design calls for the M12M to be near or around RF sources such as radios switching power supplies microprocessor clocks etc it is recommended that the M12M be tested in the target environment to identify potential interference issues prior to final design In worst case situations the M12M PCB may require an additional metal shield to eliminate ele
4. PMOTG RMC 0000 lt CR gt lt LF gt 2 Assuming that the user now desires the RMC message to be sent once each second the command string would change to PMOTG RMC 0001 lt CR gt lt LF gt NMEA Response Examples The response to the command in Example 1 above would be GPRMC hhmmss ss a ddmm mmmm n ddmm mmmm w Zz z y y d d v CC lt CR gt lt LF gt where e GPRMC is the message header e hhmmss ss is the UTC time of the position fix in hours minutes and seconds e a is the current position fix status with A designating a valid position and V indicating an invalid position e ddmm mmmm is the current latitude in degrees and minutes e n is the direction of the latitude with N indicating North and S indicating South e dddmm mmmm is the current longitude in degrees and minutes e w is the direction of the longitude with W indicating West and E indicating East e Z Z is the current ground speed in knots e y y is the current direction referenced to true North e ddmmyy is the UTC date of the position fix e d d is the magnetic variation in degrees always 0 0 with M12M e vis the direction of the variation always nulled with M12M e CC is the checksum Note that unlike the binary messages NMEA messages can vary in length If any value has not been determined yet the data position will be nulled For example if you request the RMC message
5. checksum Message length 80 bytes rr 110 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands PSEUDO RANGE CORRECTION OUTPUT REQUEST Bh Applicability M12M Positioning Receiver This parameter sets the rate at which pseudo range corrections are output from the M12M receiver when being used as a master site receiver in a real time differential system The messages return pseudo range and pseudo range corrections for up to 12 receiver channels and identify the satellite IDs that corresponds to each channel To use this output properly the receiver must have the Position Hold option enabled with the current GPS receiver position entered into the Position Hold position coordinates The assignment of satellites to channels is accomplished during normal receiver operation or may be done manually The Bh message structure handles data for up to six satellites If the M12M is tracking more than six satellites two consecutive messages are output with the additional channels in the second message Unused portions of the data structure will be filled with zeros Default Message disabled Legacy Compatibility The Bh message was generated in an identical fashion by VP receivers and also by M12 receivers with firmware revisions of v1 3 and higher EEE 111 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands PSEUDO RANGE CORRECTION OUTPUT REQUEST Bh
6. T RAIM is an algorithm in Oncore timing receivers including the M12M T that uses redundant satellite measurements to confirm the integrity of the timing solution The T RAIM approach is borrowed from the aviation community where integrity monitoring is safety critical EE _______e 22 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions In most surveying systems and instruments there are more measurements taken than are required to compute the solution The excess measurements are redundant A system can use redundant measurements in an averaging scheme to compute a blended solution that is more robust and accurate than using only the minimum number of measurements required Once a solution is computed the measurements can be inspected for blunders This is the essence of T RAIM In order to perform precise timing the GPS receiver position is determined and then the receiver is put into Position Hold mode where the receiver no longer solves for position With the position known time is the only remaining unknown When in this mode the GPS receiver only requires one satellite to accurately determine time If multiple satellites are tracked then the time solution is based on an average of the satellite measurements When the average solution is computed it is compared to each individual satellite measurement to screen for blunders A residual is computed for each satellite by differencing the so
7. The Global Positioning System is operated and supported by the U S Department of Defense and is made available for civilian use solely at its discretion The Global Positioning System is subject to degradation of position velocity and time accuracies by the Department of Defense l does not warrant or control Global Positioning System availability or performance This warranty applies around the world What This Warranty Does Not Cover a Defects or damage resulting from use of the Product in other than its normal and customary manner b Defects or damage from misuse accident or neglect c Defects or damage from improper testing operation maintenance installation alteration modification or adjustment d Defects or damage due to lightning or other electrical discharge e Product disassembled or repaired in such a manner as to adversely affect performance or prevent adequate inspection and testing to verify any warranty claim EE l 5 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 1 Introduction f Product which has had the serial number removed or made illegible g Freight costs to the repair depot How to Get Warranty Service To receive warranty service contact your Oncore reseller General Provisions This warranty sets forth the full extent of i Lotus s responsibility regarding the Product Repair replacement or refund of the purchase price at i Lotus s option is the exclus
8. Time to First Fix TTFF First Time On Initialization Shut Down Received Carrier to Noise Density Ratio C No SETTING UP RECEIVERS FOR SPECIFIC APPLICATIONS M12M as a Standard Autonomous Positioning Receiver M12M as a Positioning Receiver Using Differential Corrections M12M as a Differential Base Station M12M as a Precision Timing Receiver CHAPTER 4 ANTENNA DESCRIPTIONS M12M Antenna Type I Antenna Description Antenna Gain Pattern RF Connectors Cables Information i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Antenna Placement Antenna System RF Parameter Considerations M12M Antenna Type IT Antenna Description Antenna Gain Pattern Installation Precautions Antenna Mounting Antenna in Extreme Weather and Environmental Conditions Antenna Cable and Connector Requirements Environmental Tests CHAPTER 5 I O COMMANDS OVERVIEW T O COMMAND LIST INDEX BY BINARY COMMAND SATELLITE MASK ANGLE COMMAND Ag SATELLITE IGNORE LIST MESSAGE Am POSITION LOCK PARAMETERS MESSAGE AM MARINE FILTER SELECT COMMAND AN DATUM SELECT COMMAND Ao RTCM PORT BAUD RATE SELECT COMMAND AO DEFINE USER DATUM MESSAGE Ap PULSE MODE SELECT COMMAND AP IONOSPHERIC CORRECTION SELECT COMMAND Aq POSITION FILTER SELECT COMMAND AQ POSITION HOLD PARAMETERS MESSAGE As POSITION LOCK SELECT MESSAGE AS TIME CORRECTION SELECT Aw 1PPS TIME OFFSET COMMAND Ay 1PPS CABLE DELAY COR
9. lt 60s lt 150s default N A Not applicable Knowledge of this parameter has no effect on TTFF in this configuration First Time On When the M12M receiver powers up for the first time after factory shipment the initial date and time will be incorrect This will force the receiver into a cold power up state cold start and it will begin to search the sky for all available satellites After one satellite has been acquired the date and time will automatically be set using data downloaded from the satellite When three or more satellites are tracked automatic position computation is initiated At power down the M12M receiver does not remember its current configuration unless the receiver is fitted with an onboard lithium cell or external back up power is applied Initialization When powered up the M12M acquisition and tracking algorithms will automatically start acquiring satellites and will compute position when it acquires at least three For each of the user controlled outputs the receiver if battery backed remembers the previously requested message formats continuous or polled and the update rate If no messages were active the last time the receiver was used it waits for an input command before it outputs any other data even though it may have acquired satellites and is computing position fixes internally The M12M does not need to be initialized to its approximate position to acquire satellites and compute position
10. nor does it require a current satellite almanac However the TTFF will be considerably shorter if you help the receiver locate satellites by providing it with the current date and approximate time approximate local position and a current satellite almanac This will allow the receiver to perform a Warm Start vs a Cold Start EEE 44 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions If backup power is available the M12M retrieves its last known position coordinates from RAM when main power is reapplied and uses this information in the satellite acquisition algorithm In addition the receiver retains the almanac and last used satellite ephemeris as long as the backup power is applied If you move the receiver a great distance before using it again it will find and acquire satellites but the TTFF may be longer than normal because the receiver will start looking for the satellites that are actually visible at the last known coordinates You can initialize the new approximate position coordinates for faster TTFF if desired Each message in the I O format description in Chapter 5 shows the default value for each parameter Shut Down It is recommended that the receiver not be shut down within 35s of computing an initial 2D or 3D position fix This allows time for a full set of ephemeredes to be downloaded to RAM which may shorten the next startup time 45 i Lotus GPS Products M12M User
11. 10 is entered for alpha the maximum filtering will be done An alpha value this low must be used with caution the reported velocity will have extreme latency An alpha value of 100 will result in no filtering which is the default alpha value Default value 100 Legacy Code Compatibility The AN command structure detailed here is identical to that used on the earlier M12 GT and SL receivers EE 79 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands MARINE FILTER SELECT COMMAND AN Binary Format Query current Marine Filter status ANxC lt CR gt lt LF gt where x 1 out of range hex byte OxFF Checksum OxFO Message length 8 bytes Complete hex string to query current Marine Filter status 0x40 40 41 4E FF FO OD OA Change current Marine Filter parameter ANfC lt CR gt lt LF gt where f filter parameter 10 100 OxOA 0x64 C checksum Message length 8 bytes Response to either command ANfC lt CR gt lt LF gt where f filter parameter 10 100 OxOA 0x64 C checksum Message length 8 bytes 80 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands DATUM SELECT COMMAND Ao Applicability M12M and M12M Timing receivers The M12M has one predefined datum WGS 84 stored in non volatile memory and one user definable datum Datums are referenced by an ID number The predefined datum is number
12. Binary Format Request Pseudo Range Corrections BhmC lt CR gt lt LF gt where m mode 0 output response message once polled 1 255 response message output at indicated rate continuous 1 once per second 2 once every two seconds 255 once every 255 seconds C checksum Message Length 8 bytes Response to above command Cettt ippprrd ippprrd ippprrd ippprrd ippprrd ippprrd C lt CR gt lt LF gt where ttt GPS time ref 0 6047999 0 0 604799 9 For each of six channels i Satellite ID 0 32 0 not used 1 32 Sat ID ppp pseudo range correction 1 048 576 1 048 576cm 10 485 76 10 485 76m rr pseudorange rate correction 4096 4096mm s 4 096 4 096m s d issue of data ephemeris 0 255 C checksum Message length 52 bytes er 112 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands LEAP SECOND STATUS MESSAGE B Applicability M12M Timing and Positioning Receivers This message polls the receiver for current leap second status information that has been decoded from the Navigation Data message received from the GPS satellites The data sent back by the receiver provides specific date and time information pertaining to any future leap second addition or subtraction Leap seconds are occasionally inserted in UTC and generally occur on midnight UTC June 30 or midnight UTC December 31 The GPS control segment typically notifies GP
13. Channel 8 correlator test Bit 6 Channel 7 correlator test Bit 5 Channel 6 correlator test Bit 4 Channel 5 correlator test Bit 3 Channel 4 correlator test Bit 2 Channel 3 correlator test Bit 1 Channel 2 correlator test Bit 0 Channel 1 correlator test C checksum Message Length 10 bytes re 174 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SYSTEM POWER ON FAILURE Applicability M12M Positioning and Timing Receivers Immediately after power up the M12M s ROM is tested If this test does not pass the firmware will not execute its positioning algorithms Rather it will continuously output this message once every 10 seconds Receipt of this message indicates that the receiver will need to be repaired and or reprogrammed This feature keeps the receiver from being utilized when the ROM has been compromised and therefore unreliable helping to protect the integrity of the application Legacy Code Compatibility The Sz command was implemented in a similar fashion on GT and UT Oncore receivers 175 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SYSTEM POWER ON FAILURE Sz Binary Format SzcC lt CR gt lt LF gt where c constant equal to 0 C checksum Message length 8 bytes Complete hex string indicating a Power On Failure 0x40 40 53 7A 29 OD OA SSS 176 i Lotus GP
14. E East W West hhmmss ss UTC of position fix hh hours 00 24 mm minutes 00 59 a status A valid V invalid CC checksum 182 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGSA GPS DOP AND ACTIVE SATELLITES This command enables the GPGSA DOP and Active Satellites message and determines the rate at which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs The value of the periodic rate is retained through a power cycle only if battery backup power is applied If the receiver is not computing a position fix mode field is 1 then the xDOP fields p p q q r r will be nulled If the receiver is computing a 2 D position fix mode field is 2 then the PDOP field p p and the VDOP field r r will be nulled Only satellite IDs used in the solution are output the remaining satellite ID fields will be nulled 183 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGSA GPS DOP AND ACTIVE SATELLITES NMEA 0183 Format Set response message rate PMOTG GS
15. Gf Binary Format Query current T RAIM Alarm Setting GfxxC lt CR gt lt LF gt where xx two hex bytes OxFF OxFF C 0x21 Message Length 9 bytes Complete hex string to query current T RAIM Alarm Setting 0x40 40 47 66 FF FF21 0D OA Change T RAIM Alarm Message GfaaC lt CR gt lt LF gt where aa T RAIM alarm limit 3 10 000 in 100s of nanoseconds C checksum Message Length 9 bytes Response to either command GfaaC lt CR gt lt LF gt where aa T RAIM alarm limit 3 10 000 in 100s of nanoseonds C Checksum Message Length 9 bytes SES 150 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands A LEAP SECOND PENDING MESSAGE Gj This command polls the receiver for leap second status information decoded from the Navigation Data message The output response provides specific date and time information pertaining to any future leap second addition or subtraction Present and future leap second values are also output rounded to the nearest integer value This command only operates in a polled manner thus it must be requested each time leap second information is desired The present leap second value and future leap second value are reported from the navigation data from the satellites They do not change based on the leap second application time they will be updated based on when the navigation data is updated Leap seconds are occasion
16. Guide Revision 1 0 01May06 Chapter 5 I O Commands GPZDA NMEA TIME AND DATE This command enables the GPZDA Time and Date message and determines the rate at which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs Currently there is no mechanism to set the local zone description in the NMEA I O format and the receiver operates as if the GMT offset is set to 00 00 reporting UTC time only 191 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands a ee GPZDA NMEA TIME AND DATE NMEA 0183 Format Set response message rate PMOTG ZDA yyyy CC lt CR gt lt LF gt where yyyy update rate Once every 0 9999 seconds CC optional checksum Note the asterisk is not present unless the optional checksum is present Response to above command GPDZA hhmmss ss dd mm yyyy xx yy CC lt CR gt lt LF gt where hhmmss ss UTC time hh hours 0 23 mm minutes 0 59 ss ss seconds 0 59 99 dd day 1 31 mm month 1 12 yyyy year xx local zone hours 13 13 yy l
17. Material Thickness 0 5mm Finished Diameter of 3 1 0 20mm Approximate weight of cable 15 kg km Minimum bend radius 31mm Test voltage 1000V min Minimum insulation resistance 1000 Meg ohm km Characteristic Impedance 50 2 ohms Operating Temperature Range 40 to 105 C Standard Attenuation 0 91 dB m at 900 MHz 1 26 dB m at 1500 MHz 1 32 dB m at 1600 MHz 1 50 dB m at 1900 MHz 1 54 dB m at 2000 MHz i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 57 Chapter 4 Antenna Descriptions Antenna Placement When mounting the antenna module it is important to remember that GPS positioning performance will be optimal when the antenna patch plane is level with the local geographic horizon and the antenna has full view of the sky ensuring direct line of sight to all visible satellites over head 1st Choice Placement 2nd Choice Placement Recommended antenna placements If recommended place its are not available these may suffice CANE T Ta Figure 4 6 Proper Antenna Placement 58 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Antenna System RF Parameter Considerations Both the gain and the noise of the overall system affect the performance of the A D converter in the Oncore GPS receiver The illustration below illustrates typical values for the M12M receiver when used with the antenna and the standa
18. T RAIM Status Message is normally set up to send status strings once a second so that the user s external software can be immediately alerted to any alarm conditions EEE __________________ 49 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions This page intentionally left blank E 50 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Chapter 4 Antenna Descriptions CHAPTER SUMMARY Refer to this chapter for the following e Product descriptions for the antenna for M12M navigation and M12M Timing e Installation precautions and setup e Electrical Parameters e Mechanical Dimensions aO OOOO Sas 51 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions M12M Antenna Type Antenna Description The antenna is designed to operate with the successful family of Oncore GPS receivers as well as many GPS receivers from other manufacturers The 3V version of the GPS Antenna is specifically designed to operate with M12M Oncore receivers The antenna is a general purpose GPS active antenna designed to meet the stringent environmental and performance needs of the automotive market place The antenna design reflects high standard for performance when operating in foliage urban canyon environments and in the presence of electromagnetic interference The small footprint low p
19. The space segment is a constellation of satellites operating in 12 hour orbits at an altitude of 20 183 km 10 898 m The constellation is composed of 24 satellites in six orbital planes each plane equally spaced about the equator and inclined at 55 degrees Ground Control Segment The ground control segment consists of a master control center and a number of widely separated monitoring stations The ground control network tracks the satellites precisely determines their orbits and periodically uploads almanac ephemeris and other system data to all satellites for retransmission to the user segment User Segment The user segment is the collection of all GPS user receivers Such as your Oncore GPS Receiver and their support equipment The receiver determines position by a process known as passive multi lateration More simply the GPS receiver s position is determined by the geometric intersection of several simultaneously observed ranges satellite to receiver distances from satellites with known coordinates in space The receiver measures the transmission time required for a satellite signal to reach the receiver Transit time is determined using code correlation techniques The actual measurement is a unique time shift for which the code sequence transmitted by the satellite correlates with an identical code generated in the tracking receiver The receiver code is shifted until maximum correlation between the two codes is achieved This ti
20. XOR ed checksum 0xC4 the receiver would report an ASCII checksum of 196 i __ 135 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank SSS 136 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands COMBINED POSITION MESSAGE Ga Applicability M12M Positioning and Timing Receivers This message allows the user to enter an initial position estimate If the receiver is computing a 2D fix the receiver will ignore any attempts to change the latitude and or longitude using this command If the receiver is computing a 3D fix it will also ignore any attempts to change height with this command Under these conditions the receiver will respond with coordinates of its currently calculated location If the user inputs the Ga Combined Position message along with the Gb Combined Time and Cb Almanac Input messages to a defaulted receiver the receiver will be in a Warm Start condition resulting in a rapid TTFF This procedure should be used with care If any of the data is erroneous the TTFF time may actually be EXTENDED instead of shortened Default Values Latitude 0 Longitude 0 Height Om GPS Height Legacy Code Compatibility The Ga command was implemented in an identical fashion on the M12 Oncore receiver Earlier ONCORE receivers such as the VP GT SL and UT
21. a maximum of 6 e If the rover is receiving the corrections it will respond to the Ce messages with an Ck acknowledgement message M12M as a Precision Timing Receiver As received the M12M Timing Receiver default operating parameters are already set up for optimal operation There is no need to set the Mask Angle to 10 degrees as this is the default condition for this receiver e Enter the Position Hold Position using the As command The coordinates can either be determined by a professional site survey or you can use the Auto Survey function of the M12M timing receiver Invoking this function mode 3 of the Gd command will automatically average 10 000 position fixes and then force the receiver into Position Hold e Set the timing parameters using the Gf Ge and Hn messages Gf This message is used to set the T RAIM alarm limit The receiver defaults time is 1000ns but the user may select any value between 300 and 1 000 000ns using this command Typical values are between 500 and 1000ns o OUOU 48 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Ge This message is used to turn the T RAIM function on and off The receiver must be in Position Hold mode in order to get full functionality from the T RAIM algorithm If the receiver is left in positioning mode the T RAIM can only detect a bad satellite it cannot remove it from the time solution Hn The Hn
22. always wake up in a defaulted condition and include code in the application software to initialize the receiver every time power is cycled This code may be as simple as merely directing the receiver to output a standard Binary Position Status Data message Ha for instance or may possibly involve uploading a stored almanac switching the receiver over to NMEA mode and initializing the desired NMEA strings No matter the effect is still the same if the receiver wakes up with all setup information intact there s no harm done the initialization commands merely reinforce the configuration data already present in RAM If the receiver powers up in the defaulted mode the initialization code ensures that the receiver operates in the manner intended NOTE Receivers fitted with onboard batteries CANNOT utilize external backup power Although there are many reasons for not using a receiver fitted with a battery the three instances that come up most often are 1 Remote systems that are expected to run unattended for long periods of time The most common example of this type of situation is in the timing receivers used to keep CDMA cell sites synchronized These systems are expected to operate for 10 20 years in remote areas and having to replace batteries every 5 years or so would present a severe maintenance problem 2 Operation in continuous high temperatures Although M12M receiver is rated for operation at 85 C the lithium cells have a ser
23. and reported every five seconds then we have five second epochs Fast Switching Channel A switching channel with a sequence time short enough to recover through software prediction the integer part of the carrier beat phase a Ol 201 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Flattening A parameter used to define the shape of an ellipsoid f a b a 1 1 e2 1 2 where a semi major axis b semi minor axis e eccentricity Frequency Band A range of frequencies in a particular region of the electromagnetic spectrum Frequency Spectrum The distribution of amplitudes as a function of frequency of the constituent waves in a signal Fundamental Frequency The fundamental frequency used in GPS is 10 23 MHz The carrier frequencies L1 and L2 are integer multiples of this fundamental frequency L1 154F 1575 42 MHz L2 120F 1227 60 MHz GDOP Geometric dilution of precision See Dilution of Precision GDOP PDOP TDOP Geocenter The center of mass of the earth Geodetic Datum A mathematical model designed to best fit part or all of the geoid It is defined by an ellipsoid and the relationship between the ellipsoid and a point on the topographic surface established as the origin of datum The relationship can be defined by six quantities generally but not necessarily the geodetic latitude longitude and height of the origin the two components of the deflection of the vertical at th
24. and Timing Receivers This message allows the user to give the receiver an initial estimate of the current time and date If the receiver is tracking at least one satellite the receiver will ignore any attempts to change the time and date parameters using this command Rather the receiver will respond with currently calculated time and date If the user inputs the Gb Combined Time Ga Combined Position and Cb Almanac Input message to a defaulted receiver the receiver will be in a Warm Start condition resulting in a rapid TTFF This procedure should be used with care If any of the data is erroneous the TTFF time may actually be EXTENDED instead of shortened Default Values Time 12 00 00 Date 1 1 99 GMT offset 0 00 Legacy Code Compatibility The Gb message was implemented in an identical fashion on the M12 Oncore receiver Earlier ONCORE receivers such as the VP GT SL and UT utilized three different messages to convey this information Ac Date Aa Time Ab GMT Offset e O O O O O 139 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands COMBINED TIME MESSAGE Gb Binary Format Query Current Time Message GDxxxxxxxxxxC lt CR gt lt LF gt where XXXXXXXXXX 10 hex bytes OxFF C 0x25 Message length 17 bytes Complete hex string to query current date time and GMT offset 0x40 40 47 62 FF FF FF FF FF FF FF FF FF FF 25 OD OA Change Curr
25. ee azimuth field aaa and SNR field ss will be nulled if not needed NOTE The value shown in the SNR field ss is the same as the C No value in the 12 Channel Position Status Data Message Ha and the 12 Channel Short Position Message Hb EEE 185 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGSV NMEA GPS SATELLITES IN VIEW NMEA 0183 Format Set response message rate PMOTG GSV yyyy CC lt CR gt lt LF gt where yyyy update rate 0 9999 seconds CC optional checksum Note the asterisk is not present unless the optional checksum is present Response to above command GPGSV t m n ii ee aaa ss ii ee aaa ss ii aaa ss ii aaa ss CC lt CR gt lt LF gt where t number of messages 1 4 m message number 1 4 n number of satellites in message 1 4 For each visible satellite four groups per message ii satellite PRN number ee elevation degrees 0 90 aaa azimuth degrees True 0 359 ss SNR dB 0 99 CC checksum i 186 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPRMC NMEA RECOMMENDED MINIMUM SPECIFIC GPS TRANSIT DATA This command enables the GPRMC Recommended Minimum Specific GPS Transit Data message and determines the rate at which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this
26. from L1 Polarization Right hand circular Azimuth Coverage 360 Elevation Coverage 0 to 90 Patch Element Gain 2 0 dBic minimum at zenith 10 dBic Characteristics minimum at 0 elevation LNA Gain 25dB typical Noise Figure lt 1 5dB typical Dynamics Vibration SAE J1455 ELECTRICAL Input Voltage Range 5 0 25 Vdc CHARACTERISTICS Current Requirements 26 mA 5 Vdc typical PHYSICAL Dimensions 102 0 diameter x 82 0 height mm CHARACTERISTICS Weight 312 grams Mount Center mount M28 nut Connector N jack ENVIRONMENTAL Operating Temperature 40 C to 85 C CHARACTERISTICS Storage Temperature 40 C to 85 C Humidity 85 non condensing 30 C to 60 C UV Radiation Test JIS D0202 Sunshine Carbon Arc System Salt Spray Test Spray 5 NaCl solvent at 35 C Immersion Test 1 meter with connector sealed Transient Voltage Test 12 kV MISCELLANEOUS Optional Features Post Mount Bracket P N MNT62312B1 NOTE All performance measurements are typical and referenced to 25 C unless indicated otherwise 62 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Antenna Gain Pattern The sensitivity of an antenna as a function of elevation angle is represented by the gain pattern Some directions are much more appropriate for signal reception than others so the gain characteristics of an antenna play a significant role in the antenna s overall performance A cross sect
27. is much greater than the signal information bandwidth This is done to provide the ability to receive all satellites unambiguously and to provide some resistance to noise and multipath Spread Spectrum System A system in which the transmitted signal is spread over a frequency band much wider than the minimum bandwidth needed to transmit the information being sent eO UMM 209 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix SPS Standard Positioning Service uses the C A code to provide a minimum level of dynamic or static positioning capability The accuracy of this service is set at a level consistent with national security See Selective Availability Squaring Type Channel A GPS receiver that multiplies the received signal by itself to obtain a second harmonic of the carrier that does not contain the code modulation Used in codeless receiver designs to obtain dual frequency measurements Static Positioning Positioning applications in which the positions of static or near static points are determined SV Satellite vehicle or space vehicle Switching Channel A receiver channel that is sequenced through a number of satellite signals each from a specific satellite and at a specific frequency at a rate which is slower than and asynchronous with the message data rate TDOP Time Dilution of Precision See Dilution of Precision Time to First Fix TTFF Average time usually expressed in seconds required
28. message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs The value of the periodic rate is retained through a power cycle only if battery backup power is applied If the receiver has just powered up and has yet to compute a position fix GPS status field a is V then the time hhmmss ss and date ddmmyy fields will be nulled If the receiver is not computing a position fix sometime after the first fix the time hhmmss ss and date ddmmyy fields will be frozen If the receiver is not computing a position fix status field is V then the speed over ground z z and track made good y y fields will be nulled Note 1 The Magnetic Variation field d d will always be nulled since the M12 Oncore does not have this information Note 2 United States export laws prohibit commercial GPS receivers from outputting valid data if the calculated GPS height is greater than 18 000 meters 11 miles and the calculated 3D velocity is greater than 514 meters second 1135 miles hour If the receiver is used above both of these limits concurrently the height and velocity outputs are clamped to the maximum values In addition the latitude and longitude information will be incorrect EEE 187 i Lotus GPS Products M12M User s Guid
29. mounting e Optional on board Lithium battery Additional features specific to the M12M positioning receiver include e Support for inverse differential GPS operation e RTCM differential GPS support using second serial port e User selectable NMEA 0183 output e User controlled velocity filter Additional features specific to the M12M timing receiver include e Precise 1PPS output 25 ns accuracy w o sawtooth correction e Selectable 100PPS output e Time RAIM Time Receiver Autonomous Integrity Monitoring algorithm for checking timing solution integrity e Automatic site survey i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 1 Introduction APPLICATIONS Considering that 24 hour all weather worldwide coverage is fundamental to GPS positioning and navigation it is easy to envision a broad range of applications and a large community of GPS users Applications include the following e Automobile Navigation e Aircraft Navigation e Land Navigation e Marine Navigation e Emergency Calling e Theft Recovery e Telematics e Fleet Tracking e Routing Systems e Rail Management e Asset Management e Emergency Search and Rescue e Utility Services e Precise Time Measurement e Frequency Stabilization e Network Synchronization e Surveying and Mapping e Exploration i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 1 Introduction LIMITED WARRANTY ON I LOTUS GPS PRODUCTS
30. of the major axis of an ellipse TEE 208 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix SEP Spherical Error Probable a statistical measure of precision defined as the 50th percentile value of the three dimensional position error statistics Thus half of the results are within the 3D SEP value Sidereal Day Time between two successive upper transits of the vernal equinox One sidereal day is just under four minutes shorter than one solar day Simultaneous Measurements Measurements referenced to time frame epochs that are either exactly equal or so closely spaced in time that the time misalignment can be accommodated by correction terms in the observation equation rather than by parameter estimation Slope Distance The three dimensional vector distance from station one to station two The shortest distance a chord between two points Slow Switching Channel A switching channel with a sequencing period that is too long to allow recovery of the integer part of the carrier beat phase Solar Day Time between two successive upper transits of the sun Speed of Light SOL For GPS pseudorange calculations the speed of light is defined as 3x10 m S per GPS ICD 200 Spheroid See Ellipsoid Spread Spectrum The received GPS signal is a wide bandwidth low power signal 160 dBw This property results from modulating the L band signal with a PRN code in order to spread the signal energy over a bandwidth that
31. output one time polled or each time the almanac data changes continuously Almanac data for the GPS satellites is transmitted in words 3 through 10 of subframe 5 pages 1 through 25 and words 3 through 10 of subframe 4 pages 2 through 5 7 through 10 and 25 of the satellite broadcast data message Refer to the ICD GPS 200 for a detailed almanac data description The M12M outputs the almanac data through a series of output messages each of which is identified by the particular subframe and page numbers The data fields of each individual message correspond to words 3 through 10 of the broadcast data Each word contains 24 data bits The entire almanac data output consists of 34 output response messages corresponding to the 25 pages of subframe 5 and the 9 pages in subframe 4 that contain almanac data pages 2 through 5 7 through 10 and 25 The total message output for one output request is 1122 bytes including the Cb prefix and the checksum carriage return and line feed for each output The output message begins with subframe 5 page 1 The M12M will output about 750 bytes of message data for each one second output opportunity If selected the almanac response message is output until the total number of bytes sent in a one second epoch exceeds 750 The remainder of the almanac message is sent in the next one second epoch up to the 750 byte limit per second until all of the almanac data is output If the user issues this c
32. pages must be utilized NOTE There is no binary response to this command by the receiver The receiver immediately switches to NMEA protocol and awaits NMEA commands Legacy Code Compatibility The Ci command has been implemented in an identical fashion on virtually all VP GT and M12 Oncore positioning receivers 125 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SWITCH I O FORMAT Ci Binary Format Switch to NMEA Format command CimC lt CR gt lt LF gt where m format 0x01 NMEA C 0x2B Message length 8 bytes Complete hex string to Switch to NMEA Format 0x40 40 43 69 01 2B OD 0A There is no response message to this command SSS 126 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands RECEIVER ID Cj Applicability M12M Timing and Positioning Receivers The M12M outputs an ID message upon request The information contained in the ID string is self explanatory The model number can be used to determine the type of receiver installed Legacy Code Compatibility The Cj command has been implemented in an identical fashion on virtually all Oncore receivers 127 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands RECEIVER ID Cj Binary Format Query Receiver ID CjC lt CR gt lt LF gt where C checksum Message length 7 bytes Complete
33. parameter instructs the GPS receiver to output the 1PPS output pulse earlier in time to compensate for antenna cable delay Up to one millisecond of equivalent cable delay can be removed Zero cable delay is set for a zero length antenna cable The user should consult a cable data book for the delay per unit length for the particular antenna cable used in order to compute the total cable delay needed for a particular installation This parameter may also be employed by the user to adjust the position of the 1PPS to compensate for other system delays Range 0 000 to 0 000999999 s Default value 0 000 s Resolution 1 ns Legacy Code Compatibility The Az command was implemented in an identical fashion on UT and VP timing receivers 101 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 1PPS CABLE DELAY CORRECTION Az Binary Format Query current 1PPS Cable Delay Correction AzxxxxC lt CR gt lt LF gt where Xxxx 4 out of range hex bytes OxFF Checksum 0x3B Message length 11 bytes Complete hex string to query current user specified 1PPS Cable Delay Correction 0x40 40 41 7A FF FF FF FF 3B 0D 0A Change current 1PPS Cable Delay Correction AzttttC lt CR gt lt LF gt where tttt time offset in ns 0 999 999 ns 0 0 to 0 000999999 s C checksum Message length 11 bytes Response to either command AzttttC lt CR gt lt LF gt where tttt time offset in ns 0
34. response message once polled 1 255 response message output at indicated rate continuous 0x01 once per second 0x02 once every two seconds OxFF once every 255 seconds C checksum Message length 8 bytes Response to above command HbmayyhmsffffaaaaoocoohhhhmmmmvVVvvhddntssrr vwvvvvC lt CR gt lt LF gt Date m month 1 12 d day 1 31 yy year 1998 2079 Time h hours 0 23 m minutes 00 59 s seconds 0 60 ffff fractional second 0 999 999 999 nanoseconds Position Filtered or Unfiltered following Filter Select aaaa latitude in mas 324 000 000 324 000 000 90 90 0000 longitude in mas 648 000 000 648 000 000 180 180 hhhh GPS height in cm 100 000 1 800 000 1000 18 000m mmmm MSL height in cm always 0 000 000 with M12M Speed Heading VV 3D speed in cm s 0 51400 0 0 to 514 m s vv 2D speed in cm s 0 51400 0 0 to 514 m s hh 2D heading 0 3599 tenths of degrees 0 0 to 359 9 EEE 162 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands eeS _ _ E _ aa_ E E_ E _ _ _ _ _ _ _ _ _ SS__s Geometry dd current DOP 0 999 0 0 to 99 9 DOP PDOP for 3D fix HDOP for 2D fix 00 0 otherwise Satellite Data n number of visible satellites 0 12 t number of tracked satellites 0 12 ss receiver status msb Bits 15 13 111 3D Fix 110 2
35. s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Received Carrier to Noise Density Ratio C No The Position Status Data Message output C No for each receiver channel which can be used to determine the relative signal levels of received satellite signals refer to Figure 3 9 below C No is the received carrier to noise density ratio The units are dB Hz where No is the noise density ratio received in a 1 Hz bandwidth The C No may be converted into received signal strength using the plot in Figure 3 9 The satellite signal strength is measured at the antenna input Typical good C No numbers reported by an with a properly installed antenna system are between 40 and 55 dB Hz C No vs Signal Strength in dBm 65 T ee S MBER N N E A GH C No dB Hz 5 145 140 135 130 125 120 115 11 Signal Strength dBm Figure 3 9 Approximate Signal Strength vs Reported C No i 46 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions SETTING UP RECEIVERS FOR SPECIFIC APPLICATIONS M12M as a Standard Autonomous Positioning Receiver As supplied the M12M positioning receiver will work quite well without any operator intervention except for enabling the desired outpu
36. simultaneous GPS data is collected by two or more receivers Outage A point in time and space that the GPS receiver is unable to compute a position fix This may be due to satellite signal blockage unhealthy satellites or a dilution of precision DOP value that exceeds a specified limit P Code The protected or precise code modulated on both the L1 and L2 GPS signals The P Code is a very long about 1014 bits sequence of pseudorandom binary bi phase modulations on the GPS carrier at a chipping rate of 10 23 MHz that does not repeat itself for about 38 weeks Each satellite uses its own unique one week segment of this code which is reset each week Under anti spoofing the P Code is encrypted to form Y code The Y code is only accessible by authorized users as controlled by the U S Department of Defense PDOP Position dilution of precision a unitless figure of merit expressing the relationship between the error in user position and the error in satellite ranges Geometrically PDOP is proportional to the inverse of the volume of the pyramid formed by lines running from the receiver to four observed satellites Values considered good for positioning are small such as 3 or less Values greater than 7 are considered poor Small PDOP is associated with many or widely separated satellites and large PDOP is associated with bunched up or few satellites See Dilution of Precision Parity Error A digital message consists of ones and zeros Pa
37. those messages that contain position velocity or time or can be commanded to output the data one time upon request The rate at which the data is output in the continuous output mode is dependent on the update rate requested by the user Table 3 7 below shows the rates at which the data messages are output for each type of message depending on the setting of the continuous polled option that is part of the input command Table 3 7 Binary Mode Data Message Output Rates OUTPUT CONTINUOUS POLLED MESSAGE Type MESSAGE ID m 1 255 m 0 12 Channel Ha At user selected When requested Position Status Data update rate ASCII Position At user selected Message Eq update rate Mionrequested 12 Channel T RAIM At user selected Status Hn update rate Den Roatested When new almanac Almanac Data Cb data available When requested Visible Satellite When visibility status Status Bb changes When requested When UTC offset UTC Offset Status Bo available or when it When requested changes Leap Second Status Gj When requested M12M timing receiver only In cases where more than one output message is scheduled during the same one second interval the receiver will output all scheduled messages but will attempt to limit the total number of bytes transmitted each second to 800 bytes For the case of multiple output messages if the EEE 32 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapte
38. time position almanac data and ephemeris data HOW Handover Word The word in the GPS message that contains time synchronization information for the transfer from the C A code to the P code Refer to GPS ICD 200 for details Inclination The angle between the orbital plane of a body and some reference plane e g equatorial plane INS Inertial Navigation System which contains an Inertial Measurement Unit IMU Integer Bias Terms The receiver counts the radio waves from the satellite as they pass its antenna to a high degree of accuracy However it has no information on the number of waves to the satellite at the time it started counting This unknown number of wavelengths between the satellite and the antenna is the integer bias term Integrated Doppler A measurement of Doppler shift frequency or phase over time lonospheric Delay A wave experiences delay while propagating through the ionosphere which is non homogeneous in space and time and is a dispersive medium Phase delay depends on electron content and affects carrier signals Group delay depends on dispersion in the ionosphere as well and affects signal modulation codes The phase and group delay are of the same magnitude but opposite sign e O o U l 203 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix JPO Joint Program Office for GPS located at the USAF Space Division at El Segundo California The JPO consists of the USAF Program Mana
39. utilized three different messages to convey this information Ad Latitude Ae Longitude AT Height EE 137 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands COMBINED POSITION MESSAGE Ga Binary Format Query Current Position Command GaxxxxxxxxxxxxxC lt CR gt lt LF gt where XXXXXXXXXXXXX 13 hex bytes OxFF C 0xD9 Message length 20 bytes Complete hex string to query current Combined Position 0x40 40 47 61 FF FF FF FF FF FF FF FF FF FF FF FF FF D9 OD 0A Change Current Position Command GaaaaaoooohhhhtC lt CR gt LF gt where aaaa latitude in mas 324 000 000 324 000 000 90 to 90 0000 longitude in mas 648 000 000 648 000 000 180 to 180 hhhh height 100 000 1 800 000cm 1000 to 18000 m t height type 0 GPS 1 MSL always 0 with M12M receivers C checksum Message Length 20 bytes Response to above command GaaaaaoooohhhhtC lt CR gt LF gt where aaaa latitude in mas 324 000 000 324 000 000 90 to 90 0000 longitude in mas 648 000 000 648 000 000 180 to 180 hhhh height 100 000 1 800 000cm 1000 to 18000 m t height type 0 GPS 1 MSL always 0 with M12M receivers C checksum Message Length 20 bytes ae 138 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands COMBINED TIME MESSAGE Gb Applicability M12M Positioning
40. voltage Note that the can accept any voltage from 2 5 to 5 5 Vdc on the antenna bias pin Pin 9 5 v c e o o tf 4 3V 85C fe 3 3V 25C E 3V 40C sv 85c g 5V 25C 2 5V 40C Q a S gt 00 4 f h h 1 r i 0 0 10 0 20 0 30 0 40 0 50 0 60 0 70 0 80 0 90 0 100 0 Current to antenna through RF connector Figure 3 2 antenna drive circuit performance G 16 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Active Antenna Configuration The recommended external gain antenna gain minus cable and connector losses for the M12M is 10 to 50 dB A typical antenna system might have an active antenna such as the Antenna Type with 29 dB of gain and five meters of cable with 5 dB of loss The net external gain would then be 24 dB which is well within the acceptable range While the receiver may track satellites with gain values outside of the recommended limits performance may suffer and the receiver may be more susceptible to noise and jamming from other RF sources For more information on antennas refer to Chapter 4 M12M Receiver Electrical Connections The M12M receivers receive electrical power and receive transmit I O signals through a 10 pin power data connector mounted on the receiver Figure 3 3 below illustrates the positions of both the 10 pin header and the MMCX antenna connector Figure
41. which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs If the receiver is not computing a position fix all numeric fields a a c c e e g g will be nulled NOTE The magnetic track field c c will always be nulled since the M12 Oncore does not have this information 189 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPVTG TRACK MADE GOOD AND GROUND SPEED NMEA 0183 Format Set message output rate PMOTG VTG yyyy CC lt CR gt lt LF gt where yyyy update rate 0000 9999 seconds CC optional checksum Note the asterisk is not present unless the optional checksum is present Response to above command GPVTG a a b c c d e e f g g h CC lt CR gt lt LF gt where a a Track degrees true b T message formatting constant c c Track degrees magnetic always nulled with M12M d M message formatting constant e e speed in knots f N message formatting constant g g speed in km hr h K message formatting constant CC checksum 190 i Lotus GPS Products M12M User s
42. worst case scenarios are shown below Best Case UTC Time Correction command Aw BC time shortest command input command processing shortest command output 10 ms 50 ms 10 ms 70 ms Typical Case UTC Time Correction command TC time input anywhere across one second period command processing output anywhere across one second period following command processing 0 5s 0 05s 0 475s 1 025 s Worst Case UTC Time Correction command WC time input beginning of one second period output end of one second period 1stis 2s Note The one command where these times are not applicable is the receiver s Self Test command la The Self Test command takes 5 10 seconds to complete EOE ____________________ 39 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions DATA LATENCY The receiver can output position velocity and time data on the serial port at a maximum rate of once each second The start of the output data is timed to closely correspond with the receiver measurement epoch The measurement epoch is the point in time at which the receiver makes satellite range measurements for the purpose of computing position The first byte of serial data in the position message is output between 0 and 50ms after the most recent receiver measurement epoch Refer to Figure 3 7 for the discussions that follow Let T be the most recent measurement epoch The receiver takes about
43. 0 or 9600 baud Having a separate port allows the M12M to simultaneously accept the RTCM format data stream on the second port and process normal receiver input output on the main port i E__________ 38 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Input Output Processing Time User commands sent to the M12M are placed in an input buffer that is serviced once per second When powered on and available satellites are tracked the current receiver position is available If insufficient satellite signals are received to develop a current fix the last known position is output The message response time will be the time from the transmission of the first byte of input data to the transmission of the last byte of output data The command processing time will be skewed since the time will be dependent on when the input message buffer is processed For best case processing the input command would have to arrive just before the input buffer data is processed and the output response would have to be the first or only receiver output For worst case processing the input command would have to arrive just after the input buffer data had been processed and the output response would have to be the last receiver output Assuming 1 ms per transmission of a data byte assuming 50 ms command processing and assuming a uniform distribution for time of input command data entry the best case typical case and
44. 0 ms Time Data Latency The time data output in the current data packet i e at time Tx is the result of an LSE fit using satellite pseudorange measurements taken at time T The time estimate at T is then propagated by one second plus the computed receiver clock bias rate at time T 1 before being output at time T The resulting time data is the best estimate of local time corresponding to the Tk measurement epoch based on data available at T ONE PULSE PER SECOND 1PPS TIMING Measurement Epoch Timing The M12M receiver timing is established relative to an internal asynchronous 1 kHz clock derived from the local oscillator The receiver counts the 1 kHz clock cycles and uses each successive 1000 clock cycles to define the time when the measurement epoch is to take place The measurement epoch is the point at which the receiver captures the pseudorange and pseudorange rate measurements for computing position velocity and time When the receiver starts it defines the first clock cycle as the measurement epoch Every 1000 clock cycles from that point define the next measurement epoch Each measurement epoch is EE __LLL LLL LLLL TLLLLLL_LLLLLLLLL LLLLLL_LLLLLL_LLL_L__LLLLLL_L_LL_LLLLLLLL_ 41 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions about one second later than the previous measurement epoch where any difference from 1 000000000 seconds is the result of the rec
45. 02 once every two seconds OxFF once every 255 seconds C checksum Message length 8 bytes Response to above command Hamayyhmsffffaaaaocooohhhhmmmmaaaaoooohhhh mmmmvVVvvhddttimsidd repeat imsidd series for remaining 11 channels ssrrccooooT TushmvvwwwvC lt CR gt lt LF gt Date m month 1 12 d day 1 31 yy year 1998 2079 Time h hours 0 23 m minutes 00 59 s seconds 0 60 ffff fractional second 0 999 999 999 nanoseconds Position Filtered or Unfiltered following Filter Select aaaa latitude in mas 324 000 000 324 000 000 90 90 0000 longitude in mas 648 000 000 648 000 000 180 180 hhhh GPS height in cm 100 000 1 800 000 1000 18 000m mmmm MSL height in cm always 0 000 000 with M12M Position Always Unfiltered aaaa latitude in mas 324 000 000 324 000 000 90 90 0000 longitude in mas 648 000 000 648 000 000 180 180 hhhh GPS height in cm 100 000 1 800 000 1000 18 000m mmmm MSL height in cm always 0 000 000 with M12M EEE 156 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands Speed Heading VV 3D speed in cm s 0 51400 0 0 to 514 m s vv 2D speed in cm s 0 51400 0 0 to 514 m s hh 2D heading 0 3599 tenths of degrees 0 0 to 359 9 Geometry dd current DOP 0 999 0 0 to 99 9 DOP PDOP for 3D fix HDOP for 2D fix Satellite Data n number of visible satellit
46. 0x40 40 41 53 FF ED OD OA Change current Position Lock Select Status ASeC lt CR gt lt LF gt where e selection 0x00 Disabled 0x01 Enabled C checksum Message length 8 bytes Response to either command ASeC lt CR gt lt LF gt where e selection 0x00 Disabled 0x01 Enabled C checksum Message length 8 bytes SS 96 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME CORRECTION SELECT Aw Applicability M12M Positioning and Timing receivers This command selects the time reference either GPS or UTC used in the Ha 12 Channel Position Status Data and Hb Short Position Messages This Time command is also used to determine the synchronization point for the 1PPS timing pulse Note Ifthe receiver has not downloaded the UTC parameters portion of the almanac the receiver will output time equal to GPS time and a flag denoting the lack of UTC parameters will be set in the Ha message Once the receiver has downloaded the UTC parameters from the satellites the receiver will automatically switch the time reference to UTC if UTC mode is selected Default mode UTC Legacy Code Compatibility The Aw command has been implemented in an identical fashion on virtually all Oncore receivers EE 97 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME CORRECTION SELECT Aw Binary Format Query current UTC Time Corr
47. 1 GPS available 2 GPS differential fix ss number of sats being used 0 12 178 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands y y HDOP a a Z antenna height a a height z units M meters g g z geoidal separation g g height z units M meters t t age of differential data iiii differential reference 0000 1023 station Id CC checksum SEE 179 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank SSS 180 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGLL NMEA GEOGRAPHIC LATITUDE AND LONGITUDE This command enables the GPGLL Geographic Position Latitude Longitude message and determines the rate at which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs The value of the periodic rate is retained through a power cycle only if battery backup power is applied If the receiver has just powered up and has yet to compute a position fix GPS s
48. 16mA typical 20mA max PHYSICAL Dimensions 38 x 34 x 13 2 mm 0 5 mm CHARACTERISTICS Weight lt 89 grams including 5m cable and connector Mounting Methods Magnetic and Blind holes 2 Taplite screw size of 2 6 x 5 mm 1 mm thick base plate Radome color Black MMCxX t a plug Standard for 3 Vdc antenna Cable Connectors Antenna to receiver Single shield RG 316 type coaxial cable Interconnection 5 meters 25 ft long See connectors above ENVIRONMENTAL Operating 40 C to 100 C CHARACTERISTICS Temperature Storage Temperature 40 C to 100 C Thermal Testing Cycled 600 hours at 40 C and 100 C UV Radiation Sunshine Carbon Arc System JIS D0205 Salt Spray Test 320 hours Spray 5 NaCl solvent at 35 C Immersion Test 60 minutes at 1 meter MISCELLANEOUS Optional Features Special order model Substrate w o radome and base version with cable and connector NOTE All values above are referenced to 25 C unless indicated otherwise a OOOO ss 53 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Antenna Gain Pattern The sensitivity of an antenna as a function of elevation angle is represented by the gain pattern Some directions are much more appropriate for signal reception than others so the gain characteristics of an antenna play a significant role in the antenna s overall performance A cross sectional view of the antenna
49. 276 8 3276 7 86 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands PULSE MODE SELECT COMMAND AP Applicability M12M Timing receivers The M12M Timing receiver can output either a 1PPS or 100PPS pulse train The user selects the pulse output signal using the Pulse Mode Select command More information on the characteristics of the 100PPS signal can be found on page 3 13 Default mode 1PPS Legacy Code Compatibility The AP command structure detailed here is identical to that used on UT timing receivers 87 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands PULSE MODE SELECT COMMAND AP Binary Format Query Current Pulse Mode APxC lt CR gt lt LF gt where x 1 out of range hex byte OxFF C OxEE Message length 8 bytes Complete hex string to query current Pulse Mode 0x40 40 41 50 FF EE OD 0A Change current Pulse Mode APMC lt CR gt lt LF gt where m mode 0x00 1PPS output 0x01 100PPS output C checksum Message length 8 bytes Response to either command APmC lt CR gt lt LF gt where m mode 0x00 1PPS output 0x01 100PPS output C checksum Message length 8 bytes TTT Tee 88 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands IONOSPHERIC CORRECTION SELECT COMMAND Aq Applicability M12M Positioning and Timing receivers The user has the flex
50. 3 3 M12M Oncore Receiver a O UU 17 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions The following table lists the assigned signal connections of the M12M receiver s power data connector Table 3 1 M12M Power Data Connector Pin Assignments Pin Signal Name Description 1 TxD1 Transmit Data 3V logic 2 RxD1 Receive Commands 3V logic 3 3V PWR Regulated 3Vdc Input 4 1PPS 1 pulse per second output 5 Ground Signal and Power common 6 Battery Optional External Backup 7 Reserved Not currently used 8 RTCM In RTCM correction input 9 Antenna Bias 3V 5V antenna bias input 10 Reserved Not currently used M12M Nominal Voltage and Current Ranges Main Power Voltage 2 85V to 3 15V regulated 50 mV peak to peak ripple Current 52 mA maximum without antenna Backup Battery Externally applied backup power Voltage Current Backup power retains the real time clock position satellite data user commanded operating 2 2V to 3 2V 5 pA typical 2 7V and 25 C ambient temperature modes and message formatting 18 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions M12M ONCORE RECEIVER PRINTED CIRCUIT BOARD MECHANICAL DRAWINGS 4PLCS 0 125 2 362 60 0 3 2 OPTIONAL X BATTERY MMCX CONNECTOR 2i 0 0 ORIGIN NFS PIN 10 Ojo RFI PIN 2 sis PINS NiS e
51. 4 out of range bytes all OxFF C 0x0C Message length 11 bytes Complete hex string to query current Position Lock Parameters 0x40 40 41 4D FF FF FF FF OC OD OA Change current Position Lock Parameters AMifddC lt CR gt lt LF gt where i integer part of speed threshold f fractional part of speed threshold dd distance threshold C checksum Message length 11 bytes Response to either command AMifddC lt CR gt lt LF gt where i integer part of speed threshold f fractional part of speed threshold dd distance threshold C checksum Message length 11 bytes 0 255 m s 0x00 OxFF 0 99 cm s 0x00 0x63 0 65535 m 0x00 00 OxFF FF 0 255 m s 0x00 OxFF 0 99 cm s 0x00 0x63 0 65535 m 0x00 0x00 OxFF OxFF 78 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands MARINE FILTER SELECT COMMAND AN Applicability M12M positioning receivers The Marine Filter command controls the velocity filtering feature The velocity filter is useful in marine applications to filter out some of the wave motion in the reported velocity The filter is a single order alpha filter where alpha is the value entered by the user ranging from 10 to 100 in increments of one Alpha is then used in the filtered velocity solution representing 10 to 100 of the last calculated velocity the remainder of which uses the previously reported velocity If a value of
52. 40 40 41 4F FF F1 OD 0A Change current RTCM Port Baud Rate AObC lt CR gt lt LF gt where b RTCM port baud rate 0x00 9600 0x01 4800 0x02 2400 C checksum Message length 8 bytes Response to either command AObC lt CR gt lt LF gt where b RTCM port baud rate 0x00 9600 0x01 4800 0x02 2400 C checksum Message length 8 bytes 84 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands DEFINE USER DATUM MESSAGE Ap Applicability M12M and M12M Timing receivers The M12M can accommodate one user defined datum stored as ID number 50 The Define User Datum command allows the user to define the constants used for this datum A datum is defined by a semi major axis an inverse flattening constant and an offset from the center of mass of the earth given as delta X delta Y and delta Z parameters If the user has not supplied the receiver with custom datum parameters Datum 50 will contain WGS 84 parameters identical to those stored in the receiver s default datum Datum 49 Default value WGS 84 parameters Related command Datum Select Message Ao Legacy Code Compatibility The Ap command has been implemented in an identical fashion on virtually all Oncore receivers 85 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands DEFINE USER DATUM MESSAGE Ap Binary Format Query current User Defined Datum Parameters
53. 49 and the user definable datum is number 50 The user instructs the receiver which datum to use by sending the Datum Select command The user can instruct the GPS receiver to use the user definable datum by sending a Datum Select command with the ID option set to 50 NOTE Before Datum 50 may be used the M12M must have the user datum information programmed into it using the Ap command If this is not done Datum 50 will contain WGS 84 coordinates identical to Datum 49 Default datum WGS 84 ID code 49 Legacy Code Compatibility The Ao command has been implemented in an identical fashion on virtually all Oncore receivers The main difference is that the VP receivers had sufficient memory to hold 48 of the most commonly used datums whereas the M12M can store one EEE 81 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands DATUM SELECT COMMAND Ao Binary Format Query currently used Datum ID AoxC lt CR gt lt LF gt where x 1 out of range byte OxFF Checksum 0xD1 Message length 8 bytes Complete hex string to query current Datum ID 0x40 40 41 6F FF D1 OD OA Change currently used Datum ID AodC lt CR gt lt LF gt where d datum ID 49 or 50 0x31 or 0x32 C checksum Message length 8 bytes Response to either command AodsssffiiffffxxyyzzC lt CR gt lt LF gt where d current datum ID 49 or 50 0x31 or 0x32 sssff semi major axis m where sss i
54. 6144 00m 1111 15 6144 00m lt URA xuw n a No accuracy prediction is available unauthorized users are advised to use the SV at their own risk ss receiver status msb Bit 15 13 111 3D Fix 110 2D Fix 101 Propagate Mode 100 Position Hold 011 Acquiring Satellites 010 Bad Geometry 001 Reserved 000 Reserved Bit 12 11 Reserved Bit 10 Narrow band tracking mode timing rx only Bit 9 Fast Acquisition Position Bit 8 Filter Reset To Raw GPS Solution Bit 7 Cold Start no almanac almanac out of date or have almanac but time or position unknown Bit 6 Differential Fix Bit 5 Position Lock Bit 4 Autosurvey Mode Bit 3 Insufficient Visible Satellites Bit 2 1 Antenna Sense 00 OK 01 0C 10 UC 11 NV Bit 0 Code Location 0 EXTERNAL 1 INTERNAL rr Reserved Oscillator and Clock Parameters cc clock bias 32768 32767 ns o0ooo oscillator offset 0 250000 Hz TT oscillator temperature 110 250 half degrees C 55 0 125 0 C Time mode UTC Parameters Bit 7 1 UTC time mode enabled 0 GPS time mode enabled Bit 6 1 UTC offset decoded 0 UTC offset not decoded Bits 5 0 Present UTC offset value range 32 31 seconds from GPS time ignore if Bit 6 0 EE ________e 158 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands EEE GMT Offset s signed byte of GMT offset 0x00 positive OxFF nega
55. 9 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions SSS 60 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions M12M Antenna Type Il Antenna Description The antenna is intended for use in GPS timing applications and is designed for use with Oncore receivers as well as many GPS receivers from other manufacturers GPS signals are received by the antenna amplified within the antenna assembly and then relayed via cable to the receiver module for processing The conical radome housing is manufactured from an Ultra Violet UV resistant material A tubular mounting nut specially designed for ease of weatherproofing assures superior performance while operating in the world s most challenging weather environments 61 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Table 4 7 Antenna Technical Characteristics GENERAL Antenna Description Molded UV resistant plastic conical CHARACTERISTICS radome Aluminum die cast bottom housing Electrically shielded low noise amplifier assembly Operating Frequency L1 1575 42 MHz 2 MHz PERFORMANCE Input Impedance 50 Ohms CHARACTERISTICS VSWR 1 5 typical 1575 42 MHz Bandwidth 25 MHz typical 3dB points Filtering 40dB at 50MHz
56. 999 999 ns 0 0 to 0 000999999 s C checksum Message length 11 bytes y na 102 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands VISIBLE SATELLITE DATA MESSAGE Bb Applicability M12M Timing and Positioning Receivers This command requests the results of the most current satellite visibility computation The response message gives a summary of the satellite visibility status showing the number of visible satellites the Doppler frequency and the location of the currently visible satellites The reference position for the most recent satellite alert is the current position coordinates Note that these coordinates may not compare to the GPS receiver s actual position when initially turned on since the GPS receiver may have moved a great distance since it was last used Note Each Bb message from the M12M will contain information for a maximum of 12 satellites If less than 12 satellites are visible unneeded fields will be filled with zeros If there are more than 12 visible SVs visible then details SVID Doppler Elevation etc of ONLY the 12 highest SVs will be reported in the message Default mode Polled Legacy Code Compatibility The Bb command has been implemented in an identical fashion on virtually all Oncore receivers 103 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands VISIBLE SATELLITE DATA MESSAGE Bb Binary Fo
57. A yyyy CC lt CR gt lt LF gt where yyyy update rate 0 9999 seconds CC optional checksum Note the asterisk is not present unless the optional checksum is present Response to above command GPGSA a b cc dd ee ff gg hh ii jj kk mm nn 00 p p q q r r CC lt CR gt lt LF gt where a sat acquisition mode M manual forced to operate in 2D or 3D mode A Automatic auto switch 2D 3D b positioning mode 1 fix not available 2 2D 3 3D SVIDs used in solution cc dd ee ff gg hh ii jj kk mm nn o0 null for unused fields p p PDOP 1 0 9 9 q q HDOP 1 0 9 9 r r VDOP 1 0 9 9 CC checksum SES 184 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGSV NMEA GPS SATELLITES IN VIEW This command enables the GPGSV GPS Satellites in View message and determines the rate at which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs If the receiver is not tracking the satellite the SNR field ss will be nulled Further an entire group satellite ID field ii elevation field
58. APTER 3 RECEIVER DESCRIPTIONS CHAPTER SUMMARY Refer to this chapter for the following e Asimplified functional description of the operation of the M12M Oncore receiver e Antenna power and gain requirements e Physical size and electrical connections of the M12M Oncore receiver e _M12M Oncore receiver technical characteristics and operating features e M12M installation precautions and mounting considerations e Binary and NMEA interface protocol descriptions e Operational details of the M12M Oncore receiver SSS OUOU es 11 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions OVERVIEW The M12M Oncore receiver provides position velocity time and satellite tracking status information via a serial port A simplified functional block diagram of the M12M receiver is shown below in Figure 3 1 DIGITAL SIGNAL PROCESSING ANTENNA CONNECTOR pLCHANNEL CHANNEL 3 ANTENNA CURRENT SENSE CIRCUIT POWERIDATA CONNECTOR BATT PWR Figure 3 1 M12M Oncore Receiver Functional Block Diagram TT 12 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions The M12M Oncore receiver is capable of tracking twelve satellites simultaneously The module receives the L1 GPS signal 1575 42 MHz from the antenna and operates off the coarse acquisition C A code tracking The code tracking is carrier aided Time recovery capability is inher
59. Antenna Antenna Requirements Active antenna module powered by receiver module 80mA max 10dB to 50dB external antenna gain measured at receiver input 3 Vdc or 5 Vdc antenna power provided via header connector Serial Output Messages Latitude longitude height velocity heading time Communication Binary protocol at 9600 baud NMEA 0183 GGA GLL GSA GSV RMC VTG ZDA Software selectable output rate continuous or poll TTL interface 0 to 3 V Second COM port for RTCM input Electrical Characteristics Power Requirements 2 8 to 3 3 Vdc 50 mVp p ripple max Keep Alive BATT Power Power Consumption External 2 2 Vdc to 3 2 Vdc 5 uA typical 2 7 Vdc 25 C 155 mW 3 V without antenna Physical Characteristics Dimensions 40 0 x 60 0 x 13 0 mm 1 57 x 2 36 x 0 53 in Weight Receiver 12 5 g Connectors Data power 10 pin 2x5 unshrouded header on 0 050 in centers straight configuration RF right angle MMCX Antenna to Receiver Interconnection Single coaxial cable with power on center conductor to support active antenna Antenna sense circuit Environmental Characteristics Operating Temperature 40 C to 85 C Storage Temperature 40 C to 105 C Humidity 95 over dry bulb range of 38 C to 85 C Altitude 18 000 m 60 000 ft maximum gt 18 000 m 60 000 ft for velocities lt 515 m s 1000 knots Miscellaneous Standard Features DG
60. Compatibility The GPGGA message was output in a similar fashion by VP GT and M12 Oncore receivers Note United States export laws prohibit commercial GPS receivers from outputting valid data if the calculated GPS height is greater than 18 000 meters 11 miles and the calculated 3D velocity is greater than 514 meters second 1135 miles hour If the receiver is used above both of these limits concurrently the height and velocity outputs are clamped to the maximum values In addition the latitude and longitude information will be incorrect EEE 177 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGGA NMEAGPS FIX DATA NMEA 0183 Format Set GPGGA message rate PMOTG GGA yyyy CC lt CR gt lt LF gt where yyyy update rate CC optional checksum 0 9999 seconds Note the asterisk is not present unless the optional checksum is present Response to above command GPGGA hhmmss ss ddmm mmmm n dddmm mmmm e q SS y y a a Z g g Z t t liii CC lt CR gt lt LF gt where hhmmss ss UTC of position fix hh hours mm minutes ss ss seconds ddmm mmmm n latitude dd degrees mm mmmm minutes n direction dddmm mmmm e longitude dd degrees mm mmm minutes e direction q GPS status indicator 00 24 00 59 00 00 59 99 00 90 00 000 59 999 N North S South 000 180 00 000 59 999 E East W West 0 GPS not available
61. D Fix 101 Propagate Mode 100 Position Hold 011 Acquiring Satellites 010 Bad Geometry 001 Reserved 000 Reserved Bits 12 11 Reserved Bit 10 Receiver in narrow band tracking mode M12M timing receiver only Bit 9 Fast Acquisition Position Bit 8 Filter Reset To Raw GPS Solution Bit 7 Cold Start no almanac almanac out of date or have almanac but time or position unknown Bit 6 Differential Fix Bit 5 Position Lock Bit 4 Autosurvey Mode Bit 3 Insufficient Visible Satellites Bits 2 1 Antenna Sense 00 OK 01 Overcurrent 10 Undercurrent 11 No bias voltage Bit 0 Code Location 0 EXTERNAL 1 INTERNAL rr Reserved vvvvvv ID tag 6 characters 0x20 to 0x7e C checksum Message Length 54 bytes EE 163 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank EEEEEEEE EE SSS 164 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 12 CHANNEL TIME RAIM STATUS MESSAGE Hn Applicability M12M timing receivers This message allows the user to request output of T RAIM status information Legacy Compatibility The information in the Hn message constitutes a portion of the data in the En message utilized by the UT and VP timing receivers 165 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME RAIM STATUS MESSAGE Hn Binary Forma
62. ID with the corresponding satellite channel that the slave is tracking The user can specify up to 12 satellite corrections through the use of two back to back input commands Back to back commands must be input with no time delay in between No user intervention is required in order to have the receiver accept the corrections Naturally the corrections must be formatted properly or they will be ignored Legacy Compatibility The Ce message was used in an identical manner in the GT and M12 receivers 121 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands PSEUDO RANGE CORRECTION DATA INPUT Ce Binary Format Pseudo Range Correction Data Input for up to six satellites Cettt ippprrd ippprrd ippprrd ippprrd ippprrd ippprrdC lt CR gt lt LF gt where ttt GPS time ref 0 6047999 0 0 604799 0 i SVID 0 37 0 not used 1 37 SVID ppp pseudo range corr 1 048 576 1 048 576cm 0 01 meter resolution 10485 76 10485 76m rr pseudorange rate corr 4096 4096mm s 0 001 m s resolution 4 096 4 096m s d issue of data ephemeris 0 255 C checksum Message length 52 bytes Response to above command CkC lt CR gt lt LF gt where C checksum Message length 7 bytes er 122 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SET TO DEFAULTS COMMAND Cf Applicability M12M Timing and Positioning Receivers This com
63. M Positioning Receiver firmware supports the NMEA 0183 format for GPS data output Output of data in the NMEA 0183 standard format allows a direct interface via the serial port to electronic navigation instruments that support the specific output messages NMEA formatted messages may also be used with most commercially available mapping and tracking programs The following NMEA output messages are supported as per the NMEA 0183 Specification Revision 2 0 1 Message Description GPGGA GPS Fix Data GPGLL Geographic Position Latitude Longitude GPGSA GPS DOP and Active Satellites GPGSV GPS Satellites in View GPRMC Recommended Minimum Specific GPS Transit Data GPVTG Track Made Good and Ground Speed GPZDA Time and Date You can enable or disable each message output independently and control the update rate at which the information is output The seven NMEA messages may be individually programmed to be sent out continuously at any rate from once per second to once every 9999 seconds or may be requested as individually polled responses If back up power is applied or if the receiver has the battery option the M12M receiver retains the output settings when powered off and reconfigures itself to the same state when powered up again If no back up power is provided the receiver will start up in the default state Binary format at 9600 baud with all messages in the polled configuration each time it is powered on NMEA Commands to the Receiver All
64. NMEA commands are formatted in sentences that begin with the ASCII character and end with ASCII lt CR gt lt LF gt A five character sequence PMOTG occurs after the ASCII identifying the command as a Proprietary MOTorola GPS command A five character address occurs after the PMOTG The first two characters are the talker ID which is GP for GPS equipment and the last three characters are the sentence formatter or message ID from the list above The next four characters designate the update rate being requested The command is then terminated with an optional checksum and the normal Carriage Return Line Feed characters Several examples are shown below Note that unlike Binary messages NMEA messages are not fixed length Field widths within the message can vary depending on the contained data and are delimited by the ASCII comma character As noted above checksums are supported in NMEA protocol but are not required as they are in FEE 36 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions the binary protocol The checksum is calculated by XORing the 8 data bits of each character in the sentence between but not including the and the optional or checksum CS The high and low nibbles of the checksum byte are sent as ASCII characters NMEA Command Examples 1 Assume the user desires a single polled RMC message The required command string without the optional checksum is
65. OH i LoTus M12M GPS Receiver User s Guide INTEGRATIONS Se TAVI A a DOCUMENT PREPARED BY I LOTUS CORPOARATION PTE LTD SINGAPORE Information in this document is subject to change without notice and does not represent a commitment on the part of i Lotus Corporation Pte Ltd The software described in this document is furnished under a license agreement The software may be used or copied only in accordance with the terms of the agreement i Lotus Corporation Pte Ltd All rights reserved No part of this publication may be reproduced transmitted stored in a retrieval system or translated into any language in any means without the written permission of i Lotus WY i Lotus are registered trademarks of i Lotus Corporation Pte Ltd 2006 i Lotus Corporation Pte Ltd Printed in Singapore If you need help or have any questions regarding i Lotus GPS products contact yo ur i lotus customer representative i Lotus is an Equal Employment Opportunity Affirmative Action Employer Table of Contents CHAPTER 1 INTRODUCTION 1 OVERVIEW 2 M12M Positioning Receiver 2 M12M Timing Receiver 2 PRODUCT HIGHLIGHTS 3 APPLICATIONS 4 LIMITED WARRANTY ON I LOTUS GPS PRODUCTS 5 How to Get Warranty Service 6 CHAPTER 2 NAVSTAR GPS OVERVIEW 7 ABOUT THE GPS NAVIGATION MESSAGE 8 Space Segment 8 Ground Control Segment 8 User Segment 8 Additional Information Sources 10 CHAPTER 3 RECEIVER DESCRIPTIONS 11 OVERVIEW 12 Memory Backup 13 O
66. PS corrections at 9600 baud on COM 1 RTCM SC 104 input Type 1 and Type 9 messages for DGPS at 2400 4800 or 9600 baud on COM 2 Inverse DGPS support Optional Features Lithium battery backup 20 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions M12M TIMING RECEIVER TECHNICAL CHARACTERISTICS Table 3 3Oncore Technical Characteristics M12M Timing Model General Characteristics Receiver Architecture 12 parallel channel L1 1575 42 MHz C A code 1 023 MHz chip rate Code plus carrier tracking carrier aided tracking Tracking Capability 12 simultaneous satellite vehicles Performance Characteristics Dynamics Velocity 1000 knots 515 m s gt 1000 knots 515 m s at altitudes lt 60 000 ft 18000m Acceleration 4g Jerk 5 m s Vibration 7 7g per Military Standard 810E Acquisition Time Time To First Fix TTFF Tested at 40 C to 85 C lt 15 s typical TTFF hot with current almanac position time and ephemeris lt 40 s typical TTFF warm with current almanac position time lt 150 s typical TTFF cold No stored information lt 1 0 s internal reacquisition typical Positioning Accuracy lt 5m 1 sigma lt 10 m 2 sigma Timing Accuracy 1 Pulse Per Second PPS or 100 PPS Performance using clock granularity message lt 2 ns 1 sigma lt 6 ns 6 sigma Performance not using clock granulari
67. R ON FAILURE 175 NMEA GPGGA MESSAGE 177 GPGLL NMEA GEOGRAPHIC LATITUDE AND LONGITUDE 181 GPGSA GPS DOP AND ACTIVE SATELLITES 183 GPGSV NMEA GPS SATELLITES IN VIEW 185 GPRMC NMEA RECOMMENDED MINIMUM SPECIFIC GPS TRANSIT DATA 187 GPVTG NMEA TRACK MADE GOOD AND GROUND SPEED 189 GPZDA NMEA TIME AND DATE 191 SWITCH I O FORMAT TO BINARY 193 APPENDIX 1 GPS TERMINOLOGY 196 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 This page intentionally left blank i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter L Introduction Chapter 1 INTRODUCTION CHAPTER SUMMARY Refer to this chapter for the following e Anintroduction to GPS and the M12M Oncore receivers e A limited warranty for the receivers i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 1 Introduction OVERVIEW Nearly a decade of Global Positioning System GPS experience combined with world class expertise in semiconductor products and communications development the production of the M12M GPS receiver modules are more compact and lightweight than ever before Each channel independently tracks both code and carrier for the superior performance required in today s GPS user environment Specifically designed for embedded applications the M12M when combined with our range of active micro strip patch antennas affords the engineer new freedom in bringing GPS technology to the most demanding Original Equipme
68. RECTION COMMAND Az VISIBLE SATELLITE DATA MESSAGE Bb ALMANAC STATUS MESSAGE Bd 68 69 70 73 75 77 79 81 83 85 87 89 91 93 95 97 99 101 103 105 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 ALMANAC DATA REQUEST Be EPHEMERIS DATA INPUT Bf PSEUDO RANGE CORRECTION OUTPUT REQUEST Bh LEAP SECOND STATUS MESSAGE Bj UTC OFFSET OUTPUT MESSAGE Bo REQUEST UTC IONOSPHERIC DATA Bp ALMANAC DATA INPUT Cb PSEUDO RANGE CORRECTION DATA INPUT Ce SET TO DEFAULTS COMMAND Cf NMEA PROTOCOL SELECT Ci RECEIVER ID Cj UTC IONOSPHERIC DATA INPUT Response to Bp or Co ASCII POSITION MESSAGE Eq COMBINED POSITION MESSAGE Ga COMBINED TIME MESSAGE Gb 1PPS CONTROL MESSAGE Gc POSITION CONTROL MESSAGE Gd TIME RAIM SELECT MESSAGE Ge TIME RAIM ALARM MESSAGE Gf LEAP SECOND PENDING MESSAGE Gj VEHICLE ID Gk 12 CHANNEL POSITION STATUS DATA MESSAGE Ha 12 CHANNEL SHORT POSITION MESSAGE Hb 12 CHANNEL TIME RAIM STATUS MESSAGE Hn INVERSE DIFFERENTIAL WITH PSEUDORANGE OUTPUT Hr 12 CHANNEL SELF TEST MESSAGE Ia 107 109 111 113 115 117 119 121 123 125 127 129 133 137 139 143 145 147 149 151 153 155 161 165 167 173 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 SYSTEM POWE
69. S Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands NMEA GPGGA MESSAGE This command enables the NUEA GPGGA GPS Fix Data message and determines the rate at which the information is transmitted The periodic rate field yyyy instructs the receiver either to output this message once polled or to output this message at the indicated update rate continuously Once the receiver is set to continuous output the continuous flow can be stopped by sending a one time polled output request The receiver will output the response one final time and then terminate any further message outputs The value of the periodic rate is retained through a power cycle only if battery backup power is applied If the receiver has just powered up and has yet to compute a position fix GPS status field is 0 then the time hhmmss ss and HDOP y y fields will be nulled If the receiver is not currently computing a position fix sometime after the first fix the time field hhmmss ss will be frozen and the HDOP field y y will be nulled If the receiver is not currently receiving differential GPS corrections GPS status field q is not 2 then the age of differential data t t and differential reference station ID iiii fields will also be nulled NOTE Height reported in the GPGGA message is GPS height and the geoidal separation field g g will always be nulled since the M12 Oncore does not calculate this information Legacy Code
70. S users of pending leap second insertions to UTC several weeks before the event When a leap second is inserted the time of day will show a value of 60 in the seconds field When a leap second is removed the date will roll over at 58 seconds The current UTC offset will be zero if the receiver is set up to run in GPS time mode instead of UTC Default mode Polled Legacy Compatibility The Bj message was used in an identical manner in virtually all receivers EE 113 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands LEAP SECOND STATUS MESSAGE B Binary Format Query current Leap Second Pending information BjmC lt CR gt lt LF gt where m mode 0x00 C 0x28 Message length 8 bytes Complete hex string to query current user specified Leap Second Status 0x40 40 42 6A 00 28 0D 0A Response to above command BjmC lt CR gt lt LF gt where m leap second status 0x00 no leap second pending 0x01 addition of one second pending 0x02 subtraction of one second pending C checksum Message length 8 bytes SET 114 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands UTC OFFSET OUTPUT MESSAGE Bo Applicability M12M Timing and Positioning Receivers This message allows the user to request the UTC offset that is currently being used in the time solution The value reported is the integer number of seco
71. What This Warranty Covers And For How Long i Lotus Corporation Pte Ltd i Lotus warrants its Global Positioning System GPS Products Product against defects on material and workmanship under normal use and service for a period of twelve 12 months from Product s in service date but in no event longer than eighteen 18 months from initial shipment of the Product i Lotus at its option will at no charge either repair exchange or replace this Product during the warranty period provided it is returned in accordance with the terms of this warranty Replaced parts or boards are warranted for the balance of the original applicable warranty period All replaced parts or Product shall become the property of i Lotus Any repairs not covered by this warranty will be charged at the cost of replaced parts plus the i Lotus hourly labor rate current at that time This express limited warranty is extended by i Lotus to the original end user purchaser only and is not assignable or transferable to any other party This is the complete warranty for Products manufactured by i Lotus i Lotus does not warrant the installation maintenance or service of the Product i Lotus cannot be responsible in any way for any ancillary equipment not furnished by i Lotus which is attached to or used in connection with i Lotus s GPS Products or for operation of the Product with any ancillary equipment and all such equipment is expressly excluded from this warranty
72. a 24 bit field where each bit of the field represents the Pass Fail condition for each parameter tested Passed tests are indicated by a logic 1 while failed tests are indicated by a logic 0 When the self test is initiated the next output message may not be the response The self test may take up to ten seconds to execute Once the self test is complete the satellite acquisition process starts restarts as when the receiver was first powered on The date time position almanac and ephemeris information is all retained 173 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 12 CHANNEL SELF TEST MESSAGE la Binary Format Request Self Test Message 12 Channel laC lt CR gt lt LF gt where C 0x28 Message length 7 bytes Complete hex string to request a Self Test 0x40 40 49 61 28 OD OA Response to above command lasssC lt CR gt LF gt where sss self test results msb Bits 23 22 Antenna Sense 00 OK 01 Overcurrent 10 Undercurrent 11 No bias voltage present Bit 21 RTC comm amp time Bit 20 Temperature Sensor Bit 19 spare Bit 18 RAM Bit 17 ROM Bit 16 1 KHz presence Bit 15 spare Bit 14 Temperature Sensor Data Checksum Bit 13 Oscillator Data Checksum Bit 12 Manufacturing Data Checksum Bit 11 Channel 12 correlator test Bit 10 Channel 11 correlator test Bit 9 Channel 10 correlator test Bit 8 Channel 9 correlator test Bit 7
73. al standoffs and retained with metal English or metric screws Mounting standoffs are available in a wide variety of materials with English or metric threads Several sources are listed in Table 3 5 Key points in selecting the four screws and standoffs that will mechanically hold and secure the M12M to the application PCB are the screw sizes screw head designs and the diameter and length of the standoffs The four holes in the M12M PCB are designed to accommodate 4 40 English or 2 5 or 3mm metric mounting screws It is recommended that these screws have Philips Torx or other head designs that retain the installation tool in order to avoid component damage that may occur if the tool slips out of the screw head Recommended torque to assemble the M12M PCB to the standoffs is 6 in lb with a maximum of 7 and minimum of 5 in lb While somewhat higher torques can be tolerated use of extremely high torques can possibly crack internal clads in the four layer M12M PCB Washers are not required or recommended Standoffs should have a maximum outside diameter OD of 187 4 5mm Note that these are standard sizes and should be easy to procure from a number of sources Use of larger diameter standoffs can result in damage to small surface mount components mounted in close proximity to the mounting holes If standoffs of the recommended diameters are not available the next larger available diameter may possibly be used but fit should be carefully verif
74. ally inserted in UTC and generally occur on midnight UTC June 30 or midnight UTC December 31 The GPS control segment typically notifies GPS users of pending leap second insertions to UTC several weeks before the event When a leap second is inserted the time of day will show a value of 60 in the seconds field When a leap second is removed the date will roll over at 58 seconds The current UTC offset will be zero if UTC is disabled St 151 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands LEAP SECOND PENDING Gj Binary Format Query Current Leap Second Pending Status GjC lt CR gt lt LF gt where C 0x2D Message length 7 bytes Complete hex string to query current Leap Second Pending Status 0x40 40 47 6A 2D 0D 0A Response to above command GipfyymdiffffhmsC lt CR gt LF gt where p present leap second value f future leap second value yy year of the future leap second application m month of the future leap second application d day of the future leap second application integer part of current UTC offset seconds ffff fractional part of current UTC offset nanoseconds h hour of the leap second application 0 23 m minute of the leap second application 0 59 s second of the leap second application 0 60 C checksum Message Length 21 bytes E 152 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O C
75. an eliminate hours of troubleshooting especially in a new installation The antenna power supply circuit consists of a current sense resistor two rail to rail output operational amplifiers a pass transistor and a voltage divider to set the upper and lower limits of the under current and over current thresholds The operational amplifiers compare the voltage developed across the current sense resistor with these thresholds If the antenna is drawing 15 mA or more the first operational amplifier will produce a logic level to the digital circuits indicating that an antenna is attached If the signal is absent indicating an under current condition an alarm bit is set to alert the user Having this alarm bit high does not prevent the receiver from operating and may in fact be high all the time when utilizing an antenna with low current draw or when supplying the antenna with power through an external source using a bias T The over current detection circuit operates in a similar manner When the voltage drop across the current sense resistor is equal to the over current threshold set at about 90 mA at room temperature the output of the sense amplifier starts shutting down the pass transistor The receiver will automatically fold back the antenna feed current to approximately 45mA until the fault is cleared As with the undercurrent sensor a logic level is provided to the digital circuits to trigger an alarm bit that indicates the over current condi
76. and seconds follow this procedure 1 Divide the mas value by 3 600 000 The integer portion of the quotient constitute the whole degrees 2 Multiply the remaining decimal fraction of the quotient by 60 The integer portion of the product constitute the whole minutes 3 Multiply the remaining decimal fraction of the product by 60 The integer portion of the product constitute the whole seconds 4 The remaining decimal fraction of the product constitute the decimal seconds CONVERSION EXAMPLE Michigan Avenue Chicago IL Latitude 150748869 mas Longitude 315445441 mas 1 Latitude 150748869 mas 3600000 41 87468583 Longitude 315445441 mas 3600000 87 62373361 Whole Degrees of Latitude 41 Whole degrees of Longitude 87 2 Latitude 0 87468583 60 52 48114980 Longitude 0 62373361 60 37 42401660 Whole Minutes of Latitude 52 Whole Minutes of Longitude 37 3 Latitude 0 48114980 60 28 86898800 Longitude 0 42401660 60 25 44099600 Whole Seconds of Latitude 28 Whole Seconds of Longitude 25 4 Decimal seconds of latitude 0 868988 Decimal seconds of longitude 0 440996 The decimal seconds of both latitude and longitude are then truncated to 3 decimal places giving a final result of Latitude 41 52 28 869 Longitude 87 37 25 441 o O O ____ ___ 35 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions NMEA Protocol Support The M12
77. ange 0 000000000 to 0 999999999 s Default value 0 000000000 s Resolution 1 ns Legacy Code Compatibility The Ay command was implemented in an identical fashion on UT and VP timing receivers 99 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 1PPS TIME OFFSET COMMAND Ay Binary Format Query current 1PPS Time Offset AyxxxxC lt CR gt lt LF gt where Xxxx 4 out of range hex bytes OxFF C 0x38 Message length 11 bytes Complete hex string to query current user specified 1PPS Time Offset 0x40 40 41 79 FF FF FF FF 38 0D 0A Change current 1PPS Time Offset AyttttC lt CR gt lt LF gt where tttt time offsetinns 0 999 999 999 0 0 to 0 999999999 s C checksum Message length 11 bytes Response to either command AyttttC lt CR gt lt LF gt where tttt time offsetinns 0 999 999 999 0 0 to 0 999999999 s C checksum Message length 11 bytes SSeS 100 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 1PPS CABLE DELAY CORRECTION COMMAND Az Applicability M12M Timing Receivers The M12M timing receiver outputs a 1PPS signal the rising edge of which is placed at the top of the GPS or UTC one second time mark epoch as specified by the Time Mode command The 1PPS Cable Delay Correction command allows the user to offset the 1PPS time mark in one nanosecond increments relative to the measurement epoch This
78. ase of the signal from the same satellite measured by two receivers simultaneously A double difference measurement is obtained by differencing the single difference for one satellite with respect to the corresponding single difference for a chosen reference satellite eO O OUO E___ ___ 199 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix A triple difference measurement is the difference between a double difference at one epoch of time and the same double difference at the previous epoch of time Differential GPS solutions can be computed using either code phase or carrier phase measurements In differential carrier phase solutions the integer ambiguities must be resolved Differential Relative Positioning Determination of relative coordinates of two or more receivers that are simultaneously tracking the same satellites Dynamic differential positioning is a realtime technique achieved by sending code corrections to the roving receiver from one or more monitor stations Static differential GPS involves determining baseline vectors between pairs of receivers Dilution of Precision A description of the geometrical contribution to the uncertainty in a position fix given by the expression DOP SQRT TRACE ATA where A is the design matrix for the instantaneous position solution dependent on satellite receiver geometry The type of DOP factor depends on the parameters of the position fix solution Standard terms f
79. before the receiver has tracked any satellites and developed a position solution the response will look like this GPRMC V 5555595539 CC lt CR gt lt LF gt For the case where more than one output message is scheduled during the same one second eee ee ee eee ee ee eee eee eee eee eee ey 37 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions interval the receiver will output all scheduled messages but will attempt to limit the number of bytes transmitted each second to 400 bytes For the case of multiple output messages if the next message to be sent fits into the 400 byte length goal then the message will be output For example if messages totaling 334 bytes are scheduled to be sent and the user requests another 80 byte message then 414 bytes will actually be sent If the user requests yet another 70 byte message then its output will not be generated The order for priority of transmitting messages is simply alphabetical The NMEA messages are input and output on the primary serial port just as in binary mode For further details on the command formats see Chapter 5 of this document RTCM Differential GPS Support The M12M positioning receiver supports the RTCM SC 104 format for the reception of differential corrections The receiver employs a decoding algorithm that allows the unit to directly decode the RTCM Type 1 and Type 9 messages input on the second serial port pin 5 at 2400 480
80. bled in both the rover and base station will cancel out the ionospheric delay whereas the ionospheric correction algorithm is not as accurate Apply corrections to the receiver either through Port 1 or 2 depending upon the correction format Legal options are as follows 1 M12M rover receiver operating in binary mode Apply binary corrections from either a VP Oncore or M12M Oncore Base Station to the main serial port Pin 2 using the Ce message or apply RTCM 104 Type 1 or 9 corrections from a Coast Guard beacon or other source to the second serial port on Pin 8 Corrections may be applied at 2400 4800 or 9600 baud 2 M12M rover receiver operating in NMEA mode Corrections MUST be in RTCM 104 format and applied to the second serial port as detailed above 47 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Note that a receiver operating in differential mode will discard corrections once they have aged more than 90 seconds This is normally not a problem as corrections are typically applied every 5 20 seconds but if you have a poor RF link between the Base Station and the rover this condition may occur The receiver will automatically switch between differential and autonomous modes as corrections are received or time out M12M as a Differential Base Station In order to generate the most accurate corrections the M12M being used as a Base Station must be put in Position Hold mod
81. c input data The order for the remaining data is not important The user can insert up to about 1K of data per second into the serial port Consequently the user should be aware that the 34 total messages of 33 bytes each that make up the almanac data will take longer than one second to input into the receiver Legacy Compatibility The Cb message was used in an identical manner in virtually all earlier receivers EEE 119 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ALMANAC DATA INPUT Cb RESPONSE TO Be Binary Format Input One Almanac Data page Cbspxxx xxxC lt CR gt lt LF gt where sp subframe page subframe 5 pages 1 25 or subframe 4 pages 2 5 7 10 XXX XXxX data words words 3 10 each word is 3 bytes long format per ICD GPS 200 C checksum Message length 33 bytes Response to above command ChspC lt CR gt lt LF gt where sp subframe page subframe 5 pages 1 25 or subframe 4 pages 2 5 7 10 25 C checksum Message length 9 bytes rr 120 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands PSEUDO RANGE CORRECTION DATA INPUT Ce Applicability M12M Positioning Receivers The input message is structured to accept pseudo range and pseudo range rate corrections for up to six satellites on serial port 1 The slave receiver uses the corrections in the input message by associating the satellite
82. clude C checksum Message length 12 bytes eg 76 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION LOCK PARAMETERS MESSAGE AM Applicability M12M Positioning receivers This message allows the user to modify the default speed and distance thresholds for the Position Lock function The position reported by the receiver will be locked if the current speed and distance traveled are both less than their respective thresholds and the Position Lock function has been enabled using the AS command This function is normally employed by positioning receiver users who are displaying position on a map display With Position Lock enabled the displayed position of the receiver will not drift when the receiver is stationary sitting at a traffic light for example Under normal conditions with Position Lock OFF the displayed position will tend to wander over a 3 5 meter radius due to errors in the GPS system Default values Speed threshold 0 5 m s Distance threshold 100 m Related Command AS Position Lock Control Legacy Code Compatibility The AM command structure detailed here is identical to that used on the earlier receiver i ___ 77 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION LOCK PARAMETERS MESSAGE AM Binary Format Query current Position Lock Parameters AMxxxxC lt CR gt lt LF gt where XXXXX
83. cters 0x20 to Ox7E to input user defined ID C checksum Message length 13 bytes Response to above command GkvwvwvwvC lt CR gt LF gt where vvvvvv Current 6 character ID tag 0x20 to Ox7E C checksum Message Length 13 bytes er 154 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 12 CHANNEL POSITION STATUS DATA MESSAGE Ha This message is the standard M12M binary position status message The Ha message provides position and channel related data to the user at a specified update rate Default mode Polled Note United States export laws prohibit commercial GPS receivers from outputting valid data if the calculated GPS height is greater than 18 000 meters 11 miles and the calculated 3D velocity is greater than 514 meters second 1135 miles hour If the receiver is used above both of these limits concurrently the height and velocity outputs are clamped to the maximum values In addition the latitude and longitude information will be incorrect SS 155 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 12 CHANNEL POSITION STATUS DATA MESSAGE Ha Binary Format Request 12 Channel Position Status Data Message HarC lt CR gt lt LF gt where r Output Rate 0x00 output response message once polled 0x01 OxFF response message output at indicated rate 0x01 once per second 0x
84. ctromagnetic compatibility EMC problems Thermal Considerations The receiver operating temperature range is 40 C to 85 C and the storage temperature range is 40 C to 105 C Before installation you should perform a thermal analysis of the housing environment to ensure that temperatures do not exceed 85 C when operating 105 C stored This is particularly important if air circulation in the installation site is poor other electronics are installed in the enclosure with the M12M or the M12M is enclosed within a shielded container due to electromagnetic interference EMI requirements M12M receivers fitted with onboard lithium backup batteries present a special case Although the receiver is rated for operation to 85C the lithium cell has a recommended upper temperature limit of 60C Sustained operation at temperatures above this level may result in reduced backup time and premature battery failure Grounding Considerations The ground plane of the receiver is connected to the four mounting holes For best performance it is recommended that the mounting standoffs in the application be grounded The receiver will still function properly if it is not grounded via the mounting holes but the shielding may be less effective EEE 26 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions PCB Mounting Hardware The M12M Oncore PCB is normally mounted on round or hex female threaded met
85. d that corresponds to T based on the position and velocity data computed from measurements taken at time T In this way the position data output on epoch Tx will most closely correspond with the receiver true position when the data is output on the serial port Of course there can be a position error due to the propagation process if the receiver is undergoing acceleration The error can be as large as 4 5 m for every G of acceleration There is no significant error under stationary or constant velocity conditions Position Data Latency The position data output in the current data packet i e at time T is the result of a Least Squares Estimation LSE algorithm using satellite pseudorange measurements taken at time Tx 1 The resulting LSE position corresponding to time T 1 is then propagated one second forward by the velocity vector the result of an LSE fit using satellite pseudorange rate measurements taken at T 1 The resulting propagated position is output at the T epoch Velocity Data Latency The velocity data output in the current data packet i e at time T is the result of an LSE fit using satellite pseudorange rate measurements taken at time T The pseudorange rate measurements are derived from the difference in integrated carrier frequency data sampled at measurement epochs T and Tk 200 ms In effect the resulting velocity data represents the average velocity of the receiver halfway between T and T 1 20
86. days D Atise 128 127 seconds C checksum Message length 29 bytes 131 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank SS SSS 132 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ASCII POSITION MESSAGE Eq Applicability M12M Positioning and Timing Receivers The ASCII position output message contains position time and receiver status Information similar in scope to the Hb binary Short Position message The ASCII message may be a more convenient interface for certain applications where the ASCII output of NMEA is desired but operation at 4800 baud is not desirable The units and style of the data is similar to NMEA output Default mode Polled Legacy Code Compatibility The Eq command has been implemented in an identical fashion on GT UT and M12 Oncore receivers 133 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ASCII POSITION MESSAGE Eq Binary Format Request ASCII Position Message EqmC lt CR gt lt LF gt where m output mode 0x00 output response message once polled 0x00 OxFF response message output at indicated rate continuous 1 0x01 once per second 2 0x02 once every two seconds 255 OxFF once every 255 seconds C checksum Message length 8 bytes Respo
87. ds b a1 128 127 seconds semi circle c a2 128 127 seconds semi circle d a3 128 127 seconds semi circle e p0 128 127 seconds f 61 128 127 seconds semi circle g 2 128 127 seconds semi circle h p3 128 127 seconds semi circle UTC Data see ICD GPS 200 Table 20 IX for scale factors AAAA Ao 2 147 483 648 2 147 483 647 seconds aaaa A 8 388 608 8 388 607 seconds second d Atis 128 127 seconds t tot 0 602 112 seconds w WN 0 255 weeks W WNisr 0 255 weeks n DN 1 7 days D Atise 128 127 seconds C checksum Message length 29 bytes Response to above command CoabcdefghAAAAaaaadtwWnDC lt CR gt lt LF gt where lonospheric Data see ICD GPS 200 Table 20 X for scale factors a a0 128 127 seconds b a1 128 127 seconds semi circle c a2 128 127 seconds semi circle d 03 128 127 seconds semi circle e p0 128 127 seconds f 61 128 127 seconds semi circle g 2 128 127 seconds semi circle h p3 128 127 seconds semi circle FE 130 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands UTC Data see ICD GPS 200 Table 20 IX for scale factors AAAA Ao 2 147 483 648 2 147 483 647 seconds aaaa A 8 388 608 8 388 607 seconds second d Atis 128 127 seconds t tot 0 602 112 seconds w WN 0 255 weeks W WNLsF 0 255 weeks n DN 1 7
88. e Revision 1 0 01May06 Chapter 5 I O Commands GPRMC NMEA RECOMMENDED MINIMUM SPECIFIC GPS TRANSIT DATA NMEA 0183 Format Set message output rate PMOTG RMC yyyy CC lt CR gt lt LF gt where yyyy update rate 0000 9999 seconds CC optional checksum Note the asterisk is not present unless the optional checksum is present Response to above command GPRMC hhmmss ss a ddmm mmmm n dddmm mmmm w Z z y y ddmmyy d d v gt CC lt CR gt lt LF gt where hhmmss ss Time of position fix ref to UTC hh hours 00 24 mm minutes 00 59 ss ss seconds 00 00 59 99 a GPS status A valid V invalid ddmm mmmm n Latitude dd degrees 00 90 mm mmmm minutes 00 000 59 999 n direction N North S South dddmm mmmm w Longitude ddd degrees 00 180 mm mmmm minutes 00 000 59 9999 w direction E East W West z z speed over ground 0 0 knots y y track made good 0 0 359 9 referenced to true north ddmmyy UTC date of position fix dd day 01 31 mm month 01 12 yy year 00 99 d d magnetic Always nulled with M12M variation degrees v variation sense E East W West CC checksum TT 188 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPVTG NMEA TRACK MADE GOOD AND GROUND SPEED Applicability M12M positioning receivers This command enables the GPVTG Track Made Good and Ground Speed message and determines the rate at
89. e following Character Hexadecimal Binary H 0x45 01000101 a 0x61 01100001 XOR of 0x45 and 0x61 0x24 00100100 m 0x01 00000001 XOR of 0x24 and 0x01 0x25 00100101 The final checksum would then be 0x25 in hexadecimal The complete command would then be as follows Message format Ham C lt CR gt lt LF gt Hexadecimal 0x40 0x40 0x45 0x61 0x01 0x25 0x0D 0x0A ASCII H a A AM AJ To enter this command using the WinOncore12 software one would open the lt Msg gt window and type Ha01 lt Enter gt on the command line Note Within the WinOncore12 software characters beyond the fourth character are treated as hexadecimal numbers the checksum is computed automatically and the lt CR gt lt LF gt pair is automatically appended to the command The receiver will now output the standard 12 Channel Position Status Data message once every second TT 34 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Millisecond to Degree Conversion The primary output message of M12M receiver in binary mode is the 12 Channel Position Status Data Message Ha In this message the latitude and longitude are reported in milliarcseconds or mas An example of converting mas to degrees is illustrated below One degree of latitude or longitude has 60 arcminutes or 3600 arcseconds or 3 600 000 milliarcseconds To convert the positive or negative milliarcseconds to conventional degrees minutes
90. e origin and the geodetic azimuth of a line from the origin to some other point Geoid The particular equi potential surface which coincides with mean sea level and which may be imagined to extend through the continents This surface is perpendicular to the force of gravity at all points Geoid Height The height above the geoid is often called elevation above mean sea level GPS Global Positioning System consisting of the space segment up to 24 NAVSTAR satellites in six different orbital planes the control segment five monitor stations one master control station and three uplink stations and the user segment GPS receivers NAVSTAR satellites carry extremely accurate atomic clocks and broadcast coherent simultaneous signals EE 202 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix GPS ICD 200 The GPS Interface Control Document is a government document that contains the full technical description of the interface between the satellites and the user GPS receivers must comply with this specification if they are to receive and process GPS signals properly Gravitational Constant The proportionality constant in Newton s Law of Gravitation G 6 672 x 10 Nm7 Kg Greenwich Mean Time GMT See Universal Time HDOP Horizontal dilution of precision See Dilution of Precision Hot Start Typical time a GPS receiver requires to develop a fix after application of power given that the receiver has stored
91. e s masteR SEGMENT we CONTROL w STATION CONTROL SEGMENT SITE LOCATIONS UPLINK STATIONS MASTER CONTROL STATION COLORADO SPRINGS MONITOR STATIONS COLORADO SPRINGS CO ASCENSION DIEGO GARCIA KWAJALEIN UPLINK STATIONS poco Be KWAJALEIN Figure 2 1 NAVSTAR GPS Segments The GPS navigation message is the data supplied to the user from a satellite Signals are transmitted at two L band frequencies L1 and L2 to permit corrections to be made for ionospheric delays in signal propagation time in dual frequency receivers The L1 carrier is modulated with a 10 23 MHz precise P code ranging signal and a 1 023 MHz coarse acquisition C A code ranging signal NOTE The P Code is intended for military use and is only available to authorized users using special receivers The P and C A codes are pseudo random noise PRN codes in phase quadrature The L2 signal is modulated with the P code only Both the L1 and L2 signals are also continuously modulated with a data stream at 50 bits per second The P code is a PRN sequence with a period of 38 weeks The C A code is a shorter PRN sequence of 1023 bits having a period of one millisecond i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions The navigation message consists of a 50 bit per second data stream containing information enabling the receiver to perform the computations required for successful navigation Each satellite has its own uni
92. e satellite time frame Range Rate The rate of change of range between the satellite and the receiver The range to a satellite changes due to both satellite and receiver motion Range rate or pseudorange rate is determined by measuring the Doppler shift of the satellite signal s carrier frequency eO Oll 207 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix RDOP Relative dilution of precision See Dilution of Precision Reconstructed Carrier Phase The difference between the phase of the incoming Doppler shifted GPS carrier and the phase of a nominally constant reference frequency generated in the receiver For static positioning the reconstructed carrier phase is sampled at epochs determined by a clock in the receiver The reconstructed carrier phase changes according to the continuously integrated Doppler shift of the incoming signal biased by the integral of the frequency offset between the satellite and receiver reference oscillators The reconstructed carrier phase can be related to the satellite to receiver range once the initial range or phase ambiguity has been determined A change in the satellite to receiver range of one wavelength of the GPS carrier 19 cm for L1 will result in a one cycle change in the phase of the reconstructed carrier Relative Navigation A technique similar to relative positioning except that one or both of the points may be moving The pilot of a ship or an aircraft may need t
93. e visible using the stored almanac information and then proceeds to develop fix information outputting data in the same formats that were active when power was removed eO OOOO 13 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Operating Without a Backup Source Without any backup power none of the setup information mentioned above is available to the receiver upon restart The receiver must now perform a Cold Start where position time and almanac information are not available Note that this is not a serious problem but Time To First Fix TTFF will be somewhat longer than if the information had been available The main thing the system designer must keep in mind is that a receiver coming up in a Cold Start scenario is defaulted to Binary protocol and NO MESSAGES are ACTIVE The receiver is running through its normal housekeeping routines developing new fix data etc but it will not send any of this data out of the serial port until it is requested If the receiver is being used as part of a larger system where the user has access to the receiver s serial port through application software such as WinOncore12 the user can simply use the software to reinitialize the receiver into the desired mode Embedded developers have to be careful since they typically do not have direct access to the receiver s serial port In this case the best thing to do is to ASSUME that the receiver will
94. e with the antenna at an accurately surveyed position The positioning accuracy of all of the rover receivers is limited by the accuracy of this position To set up a Base Station the following steps should be followed e Disable the ionospheric and tropospheric corrections by invoking mode 0 in the Aq lonospheric Corrections Select Command e Set the satellite mask angle to 10 degrees using the Ag command e Enter the Position Hold Position using the As command The coordinates can either be determined by a professional site survey or you may use the Base Station receiver along with a software program such as WinOncore12 to develop a reasonably accurate position by allowing the receiver to run for 12 24 hours and utilize the Mean position calculated by the software e Place the receiver in Position Hold mode by invoking mode 1 of the Gd Position Control Message e Enable the output of differential corrections from the base station using the Bh command Allowable update rates are once per second to once per 255 seconds As a practical matter corrections are usually sent out every 3 20 seconds Any longer than a 20 second update rate may tend to cause larger errors in reported position Once the Bh command is invoked the base station will start issuing Ce correction messages at the requested rate Two Ce messages will be issued back to back if more than 6 satellite corrections are available as the Ce message format only handles
95. ection Option AwxC lt CR gt lt LF gt where x 1 out of range hex byte OxFF C 0xC9 Message length 8 bytes Complete hex string to query current Time Correction Option 0x40 40 41 77 FF C9 0D 0A Change current UTC Time Correction Option AwmC lt CR gt lt LF gt where m time mode 0x00 GPS 0x01 UTC C checksum Message length 8 bytes Response to either command AwmC lt CR gt lt LF gt where m time mode 0x00 GPS 0x01 UTC C checksum Message length 8 bytes SR Re 98 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 1PPS TIME OFFSET COMMAND Ay Applicability M12M Timing Receivers The M12M outputs a one pulse per second 1PPS signal with the rising edge placed on top of the UTC or GPS one second tic mark depending on which time reference has been selected by the user The 1PPS Time Offset command allows the user of M12M Timing Receivers to offset the 1PPS time mark in one nanosecond increments This offset can be used to place the 1PPS signal anywhere within the one second epoch The resolution of this parameter is one nanosecond This does not imply that the 1PPS output by the M12M is accurate to this level This command only allows the user to change the location of the average placement of the pulse The absolute accuracy of the signal is a function of GPS time accuracy and is subject to degradation due to U S Department of Defense policy R
96. ed All dimensions are in mm and are for reference purposes only Antenna Type Active Substrate Top View z 22 0 21 0 Antenna Element PCB Ceramic Front View CONNECTOR aa CABLE Shield Metal Figure 4 4 Antenna Substrate Configuration EE _ 56 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions RF Connectors Cables Information Shikoku 1 5DS QEHV coaxial cable is used in the antenna assemblies This cable is very similar to RG 316 Figure 4 5 shows simplified views of the cable construction while Table 4 8 details the electrical and mechanical characteristics Jacket Sheath Heat Resistant PVC Black Outer Conductor Tinned annealed copper wire braid v Dielectric Insulation Cross linked polyethylen Cross section ps Center Inner Conductor Stranded tinned anneal concentric copper wire __ m Center Dielectric lt Conductor Jacket Outer Conductor Figure 4 5 Antenna Cable Construction Table 4 4 Characteristics of coaxial cable Item Specification Tinned Annealed Copper Wire 0 54mm diameter 7strands of 0 18 mm 120 ohms km Center Conductor Maximum inner conductor resistance 20 C Dielectric Insulation Cross linked polyethylene thickness 0 53mm Outer Conductor Tinned annealed copper wire braid outside diameter 1 6mm Jacket Sheath
97. ed to facilitate rapid satellite acquisition The orbital information in the almanac is less accurate than the ephemeris but valid for a longer time one to two years Ambiguity The unknown integer number of cycles of the reconstructed carrier phase contained in an unbroken set of measurements from a single satellite pass at a single receiver Argument of Latitude The sum of the true anomaly and the argument of perigee Argument of Perigee The angle or arc from the ascending node to the closest approach of the orbiting body to the focus or perigee point as measured at the focus of an elliptical orbit in the orbital plane in the direction of motion of the orbiting body Ascending Node The point at which an object s orbit crosses the reference plane i e the equatorial plane from south to north Azimuth A horizontal direction expressed as the angular distance between a fixed direction such as north and the direction of the object Bandwidth A measure of the information carrying capacity of a signal expressed as the width of the spectrum of that signal frequency domain representation in Hertz Hz Baseline The three dimensional 3D vector distance between a pair of stations for which simultaneous GPS data has been collected and processed with differential techniques Beat Frequency Either of two additional frequencies obtained when signals of two frequencies are mixed The beat frequencies are equal to the sum or differ
98. eeping Output Data Timing Relative To Measurement Epoch 1 SECOND 1PPS eS ee r gt lt 0 1 ms Tk 1 Tk MEASUREMENT EPOCHS SERIAL LOX NOOO ACTIVITY EET an lt 0 50 ms 1PPS CABLE DELAY AND 1PPS OFFSET 0 Figure 3 8 Output Signal Timing The 12 Channel Position Status Data Messages Ha and Hb the T RAIM Setup and Status Message H h and the Time Message Gb are the only output messages containing time information If enabled these messages will be output from the receiver shortly after a measurement epoch Generally the first data byte in the first message will be output EE ________e 42 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions between 0 to 50 ms after a measurement epoch For the Position Status Data Message the time output in the message reflects the best estimate of the most recent measurement epoch A simple timing diagram is shown in figure 3 8 1PPS Cable Delay Correction and 1PPS Offset M12M Timing Receiver Only Users can compensate for antenna cable length with the 1PPS Cable Delay Command Az The 1PPS can also be positioned anywhere in the one second window using the 1PPS Offset command Ay The rising edge of the 1PPS is placed so that it corresponds to the time indicated by the following equation 1PPS rising edge time top of second 1PPS cable delay 1PPS offset Consider the following exa
99. eiver local oscillator intentional offset about 60 us s and the oscillator s inherent instability 30 ppm over specified temperature range When the M12M processor computes receiver local time this time corresponds to the time of the last receiver measurement epoch The Oncore process precisely determines this time to an accuracy of approximately 20 to 300 ns depending on satellite geometry and the effects of Selective Availability if Selective Availability were to ever be reactivated by the DoD The computed time is relative to UTC or GPS time depending on the time type as specified by the user using the Time Mode command Aw The Oncore system timing is designed to slip time when necessary in discrete one millisecond intervals so that the receiver local time corresponds closely to the measurement epoch offset The Oncore observes the error between actual receiver local time and the desired measurement epoch offset and then slips the appropriate integer milliseconds to place the measurement epoch to the correct integer millisecond When a time skew occurs such as after initial acquisition or to keep time within limits due to local oscillator drift the receiver lengthens or shortens the next processing period in discrete one millisecond steps The rising edge of the 1PPS signal is the time reference The falling edge will occur approximately 200 ms 1 ms after the rising edge The falling edge should not be used for accurate time k
100. emonics shown in the following table are only to be used with the Extra Message window in WinOncore12 Each mnemonic causes WinOncore12 to run a macro that sends a properly formatted string to the along with the checksum carriage return and line feed See the WinOncore12 help files for further explanation in the use of these commands EEE 69 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 0 COMMAND LIST INDEX BY BINARY COMMAND Table 5 1 Input Commands Listed by Binary Command Header Binary Function Description vinonoor e M12M Mi 2M Page Command Mnemonic Timing Ag Satellite Satellite Mask Angle mask y y 73 Am Receiver Satellite Ignore List ignore y y 75 AM Position Position Lock lockp V 77 Parameters AN Setup Marine Filter Select filter y 79 Ao Setup Datum ID Codes datum y y 81 AO Setup RTCM Port Baud Rate p2baud V 83 Select Ap Setup User Defined Datum udatum y y 85 AP Timing 1PPS 100PPS Select pps100hz y 87 Aq Setup lonospheric Correction ion V V 89 Select AQ Position Position Filter Select pfilter y y 91 As Timing Position Hold php N N 93 Parameters AS Position Position Lock Select locke y 95 Aw Time UTC Correction Select utc y y 97 Ay Time 1PPS Offset ppsoff y 99 Az Time 1PPS Cable Delay ppsdelay y 101 Bb Satellite Satellite Visibility vis N J 103 Message Bd Almanac Alma
101. ence of the original frequencies Bias See Integer Bias Terms Binary Bi phase Modulation Phase changes of either zero or 180 degrees representing a binary zero or one respectively on a constant frequency carrier GPS signals are bi phase modulated 197 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Binary Pulse Code Modulation Pulse modulation using a string of binary numbers codes This coding is usually represented by ones and zeros with definite meanings assigned to them such as changes in phase or direction of a wave Bluebook A slang term derived from a blue NGS reference book The book contains information and formats required by NGS for survey data that is submitted to be considered for use in the national network C A Code The Coarse Acquisition or Clear Acquisition code modulated onto the GPS L1 signal This code is a sequence of 1023 pseudorandom binary bi phase modulations on the GPS carrier at a chipping rate of 1 023 MHz thus having a code repetition period of one millisecond This code was selected to provide good acquisition properties Carrier A radio wave having at least one characteristic such as frequency amplitude phase that may be varied from a known reference value by modulation Carrier Beat Phase The phase of the signal that remains when the incoming Doppler shifted satellite carrier signal is beat the difference frequency signal is generated with the nominally constan
102. ent Time Message GbmdyyhmsshmC lt CR gt LF gt where Date m month 1 12 d day 1 31 yy year 1982 2100 Time h hours 0 23 m minutes 0 59 s seconds 0 59 s signed byte of GMT offset 00 positive 255 negative h hour of GMT offset 0 23 m minutes of GMT offset 0 59 C checksum Message Length 17 bytes T 140 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands Response to above command GbmdyyhmsshmC lt CR gt LF gt where Date m month 1 12 d day 1 31 yy year 1982 2100 Time h hours 0 23 m minutes 0 59 s seconds 0 59 s signed byte of GMT offset 00 positive 255 negative h hour of GMT offset 0 23 m minutes of GMT offset 0 59 C checksum Message Length 17 bytes aO UO O UOO es 141 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank SS 142 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 1PPS CONTROL MESSAGE Gc Applicability M12M Positioning and Timing Receivers This message allows the user to choose how the 1PPS output from the receiver will behave Note that the allowable options are different depending upon whether the user is working with an M12M timing or positioning receiver Default mode Continuous Legacy Code Compatibility The Gc command was imp
103. ent in the architecture The L1 band signals transmitted from GPS satellites are typically collected filtered and amplified by microstrip patch antennas such as the Type or Type Il Signals from the antenna module are then routed to the RF signal processing section of the M12M via a single coaxial interconnecting cable This interconnecting cable also provides bias power for the low noise amplifier LNA in the antenna The is capable of providing the antenna with voltages from 2 5 5 5V at currents up to 80mA The RF signal processing section of the M12M printed circuit board PCB contains the required circuitry for down converting the GPS signals received from the antenna module The resulting intermediate frequency IF signal is then passed to the twelve channel code and carrier correlator section of the M12M where a single high speed analog to digital A D converter converts the IF signal to a digital sequence prior to channel separation This digitized IF signal is then routed to the digital signal processor where the signal is split into twelve parallel channels for signal detection code correlation carrier tracking and filtering The processed signals are synchronously routed to the position microprocessor MPU section This section controls the receiver operating modes decodes and processes satellite data and the pseudo range and delta range measurements used to compute position velocity and time In addition the position process
104. erent depending upon whether the user is working with an M12M timing or positioning receiver Default mode Continuous Legacy Code Compatibility The Gd command was implemented in a similar fashion on the M12 Oncore receivers This message combines the functionality of the At and Av commands used on 8 channel positioning and timing receivers 145 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION CONTROL MESSAGE Gd Binary Format Query Current Position Control Mode GdxC lt CR gt lt LF gt where x 1 hex byte OxFF C 0xDC Message length 8 bytes Complete hex string to query current Position Control Mode 0x40 40 47 64 FF DC OD OA Change Current Position Control Mode Message GdcC lt CR gt LF gt where c control type 0x00 enable normal 3D positioning 0x01 enable position hold 0x02 enable 2D positioning positioning receivers only 0x03 enable auto survey timing receivers only C checksum Message Length 8 bytes Response to above command GdpC lt CR gt LF gt where c control type 0x00 enable normal 3D positioning 0x01 enable position hold 0x02 enable 2D positioning positioning receivers only 0x03 enable auto survey timing receivers only C checksum Message Length 8 bytes Yl ee 146 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME RAIM SELECT MESSAGE Ge Applicabi
105. es 0 12 t number of tracked satellites 0 12 Channel Data i SVID 0 37 m mode 0 8 where 0 Code Search 5 Message Sync Detect 1 Code Acquire 6 Satellite Time Available 2 AGC Set 7 Ephemeris Acquire 3 Freq Acquire 8 Available for Position 4 Bit Sync Detect s signal strength 0 255 IODE 0 255 dd channel status 16 bits msb Bit 15 Reserved Bit 14 Reserved Bit 13 Reserved Bit 12 Narrow band search mode timing rx only Bit 11 Channel used for time solution Bit 10 Differential Corrections Available Bit 9 Invalid Data Bit 8 Parity Error Bit 7 Channel used for position fix Bit 6 Satellite Momentum Alert Flag Bit 5 Satellite Anti Spoof Flag Set Bit 4 Satellite Reported Unhealthy Bits 3 0 Satellite Accuracy per para 20 3 3 3 1 3 of ICD GPS 200 0000 0 0 00m lt URA lt 2 40m 0001 1 2 40m lt URA lt 3 40m 0010 2 3 40 m lt URA lt 4 85m 0011 3 4 85m lt URA lt 6 85m 0100 4 6 85m lt URA lt 9 65m 0101 5 9 65m lt URA lt 13 65m 0110 6 13 65m lt URA lt 24 00m 0111 7 24 00m lt URA lt 48 00m 1000 8 48 00m lt URA lt 96 00m 1001 9 96 00m lt URA lt 192 00m 1010 10 192 00m lt URA lt 384 00m 1011 11 384 00m lt URA lt 768 00m EEE 157 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands Coe LLO T URA continued 1100 12 768 00m lt URA lt 1536 00m 1101 13 1536 00m lt URA lt 3072 00m 1110 14 3072 00m lt URA lt
106. essage holdcon y y 145 Ge Time T RAIM Select Message tr12en y 147 Gf Time T RAIM Alarm Message trmalrm y 149 Gj Time Leap Second Pending leap12 y y 151 Gk Setup Vehicle Identification vin y V 153 Ha Position 12 Channel Position Status Data ps12 y V 155 Hb Position 12 Channel Short Position psd J J Message i Hn Time 12 Channel T RAIM Status traim12 Message y ts Hr DGPS Inverse DGPS Pseudorange y 167 la Setup 12 Channel Self Test selftest12 y y 173 sz Receiver System Power On Failure 9 y V 175 GPGGA NMEA GPS Fix Data wee y 177 GPGLL NMEA Geographic Latitude Longitude y 181 GPGSA NMEA GPS DOP and Active Satellites y 183 GPGSV NMEA GPS Satellites in View V 185 GPRMC NMEA Recommended Minimum Data V 187 GPVTG NMEA Track Made Good and Speed y 189 GPZDA NMEA Time andDate J y 191 FOR NMEA Switch to Binary sre y 193 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 71 Chapter 5 I O Commands This page intentionally left blank SSS 72 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SATELLITE MASK ANGLE COMMAND Ag Applicability M12M Positioning and Timing receivers The receiver will attempt to track satellites for which the elevation angle is greater than the satellite mask angle This parameter allows the user to control the elevation angle
107. essage length and format 30 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Binary Data Sequence A variable number of bytes of binary data dependent on the command type Checksum The Exclusive Or of all bytes after the and prior to the checksum Message Terminator 0x0D Ox0A Carriage Return Line Feed pair denoting the end of the binary message Almost all receiver input commands have a corresponding response message so that you can determine whether the input command s have been accepted or rejected by the receiver The message format descriptions in Chapter 5 detail the input command and response message formats Information contained in the data fields is normally numeric The interface design assumes that the operator display is under the control of an external system data processor and that display and message formatting code reside in its memory This approach gives you complete control of the display format and language All M12M receivers read command strings in the input buffer once per second If a full command has been received the receiver operates on that command and performs the indicated function Input character string checks are performed on the input commands A binary message is considered to be valid if it began with the characters the message is the correct length for its type the checksum validates and the command is terminated with a CR LF pair Imp
108. for a given GPS receiver to develop a position fix after power is applied For receivers first fix is defined as a 2D fix for positioning receivers and a3D fix for timing receivers See Cold Start Hot Start and Warm Start TOW Time of week in seconds from midnight Saturday UTC T RAIM Time Receiver Autonomous Integrity Monitoring This is an algorithm that continuously monitors the integrity of the time solution by using redundant satellite measurements This algorithm is only available on the M12M timing receiver See the T RAIM Setup and Status Message H n in Chapter 5 Translocation A version of relative positioning that makes use of a known position such as an NGS survey mark to aid in accurately positioning a desired point The position of the mark determined using GPS is compared with the accepted value The three dimensional differences are then used in the calculations for the second point EEE 210 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Tropospheric correction The correction applied to the measurement to account for tropospheric delay This value is normally obtained from the modified Hopfield model the parameters of which are broadcast by the satellites True Anomaly The angular distance measured in the orbital plane from the earth s center occupied focus from the perigee to the current location of the satellite orbital body Universal Time Local solar mean t
109. ft for velocities lt 515 m s 1000 knots Miscellaneous Standard Features Position hold with automatic site survey Clock granularity error message T RAIM Timing Receiver Autonomous Integrity Monitoring Optional Features Lithium battery backup 21 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions RF J amming Immunity M12M Timing Receiver Only Many precise timing GPS installations require locating the GPS antenna at close range to other systems Some of these transmitters may randomly cause the GPS receiver to lose lock on tracked satellites This can be very disconcerting to the timing user since the system must rely on clock coasting until the satellite signals are reacquired Long coasting times require more expensive oscillators for the timing electronics in order to meet system specifications for holdover capability Experience has shown that receiver selectivity or the ability to select only the GPS band of information and reject all other signals is an important feature for GPS receivers especially in cases such as those often encountered in timing applications Adaptive Tracking Loops M12M Timing Receiver Only The jamming immunity of the M12M Oncore timing receiver is done by an innovative software technique to further improve the immunity The technique takes advantage of the fact that for precise timing applications the receiver is not mov
110. gain pattern along a fixed azimuth in a vertical cut is displayed in the following figure The gain pattern clearly indicates that the antenna is designed for full upper hemispherical coverage with the gain diminishing at low elevations This cross section is representative of any vertical cross section over a full 360 degree azimuth range and thus the 3 dimensional gain pattern is a symmetric spheroidal surface It is important to note that this gain pattern varies in elevation angle but not in horizontal azimuth This design is well suited for many GPS applications accommodating full sky coverage above the local horizon and minimizing ground reflected multipath effects Amoplitude dB eae F ae Zz Frequency orien Ports 1 r AGAC 1 78 dB Beam Pegkm 3 50 dB 2 000 deg p Figure 4 2 Typical Antenna Gain Pattern 54 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Mechanical Dimensions All dimensions are in mm and are for reference purposes only 38 0 0 5 CONNECTOR 34 0 0 5 Rt Angle MCX MMCX f St SMA SMB So i 26 6 0 2 Ref Magnet 2x 2 Blind Holes Direct M ount 15 040 2 a Bottom Radome 4 940 5 Figure 4 3 Magnet Direct Mount Configuration eU 55 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Mechanical Dimensions Continu
111. ger and Deputy Program Managers representing the Army Navy Marine Corps Coast Guard Defense Mapping Agency and NATO Kalman Filter A numerical method used to track a time varying signal in the presence of noise If the signal can be characterized by some number of parameters that vary slowly with time then Kalman filtering can be used to tell how incoming raw measurements should be processed to best estimate those parameters as a function of time Kinematic Surveying A form of continuous differential carrier phase surveying requiring only short periods of data observations Operational constants include starting from or determining a known baseline and tracking a minimum of four satellites One receiver is statically located at a control point while others are moved between points to be measured Keplerian Orbital Elements Allow description of any astronomical orbit The six Keplerian orbital elements are as follows a semi major axis e eccentricity w argument of perigee 62 right ascension of ascending node i inclination of orbital plane To epoch of perigee passage L1 L2 The L band signals radiated by each NAVSTAR satellite The L1 signal is a 1575 42 MHz carrier modulated with both the C A and P codes and with the NAV message The L2 signal is a 1227 60 MHz carrier modulated with the P code and the NAV message Under anti spoofing the P code becomes the encrypted Y code for authorized users only Lane The a
112. he Northern Hemisphere Warm Start Typical time a GPS receiver requires to develop a fix after application of power given that the receiver has stored time position and almanac data e OUOU 211 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06
113. hex string to query Receiver ID 0x40 40 43 6A 29 OD 0A Response to above command The response is output as a 25 column by 12 row array General format is as shown below a e ee odes Bs Fes sila Ss eelef tetee kth eti Feit 2 ole tektek t hle ehe e eh et fo ff fo fo e a a fo ee et fel fede fn fof fa fo fox x x x a of x ele so T WJA TRIE RJEJV X X X X xX X X X X er S JOJF TI WJA JRE DJA TIE X X 1X X X 1X 1X xhel mfofofe A TTL eff x x x a xtpl e ele wf fed p a a a fo fo ff of oe fs fe A et ee fafa ff fo fe J a of a of fo a fe r ole oe fel eee TT TTT TT PTET T ETT TTT E PEE C Hex checksum Message Length 294 bytes 128 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands UTC IONOSPHERIC DATA INPUT Response to Bp or Co Applicability M12M Timing and Positioning Receivers As well as being the response to the Bp message this message allows the user to input UTC and ionospheric data into the receiver which is then echoed in the response aO O EEE Mnl 129 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands UTC IONOSPHERIC DATA INPUT Response to Bp or Co Binary Format Change UTC lonospheric Data CoabcdefghAAAAaaaadtwWnDC lt CR gt lt LF gt where lonospheric Data see ICD GPS 200 Table 20 X for scale factors a a0 128 127 secon
114. ibility of turning the GPS ionospheric and or tropospheric correction models on or off The models do a reasonable job of taking out the range error induced by the earth s ionosphere and troposphere by using algorithms and parameters transmitted to the users by the satellites For some applications such as differential systems the models should be disabled since the differential corrections include the errors Default modes lonospheric model enabled Tropospheric model disabled Legacy Code Compatibility The Ap command has been implemented in a similar fashion on virtually all Oncore receivers Some earlier receivers did not support all four of the modes available with the M12M but the message structure is identical 89 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands IONOSPHERIC CORRECTION SELECT COMMAND Aq Binary Format Query current lonospheric Correction Selection AqxC lt CR gt lt LF gt where x 1 out of range byte OxFF C CF Message length 8 bytes Complete hex string to query current lonospheric Correction Selection 0x40 40 41 71 FF CF OD OA Change current lonospheric Correction Selections AqsC lt CR gt lt LF gt where s selection 0x00 both models disabled 0x01 ionospheric model enabled 0x02 tropospheric model enabled 0x03 both models enabled C checksum Message length 8 bytes Response to either command AqsC lt CR gt lt LF gt
115. ied before committing to large scale production Obviously the height of the standoffs will be determined by the components that are populated on the application PCB especially the height of the 10 pin receptacle See Figures 3 4 which are outline drawings of the M12M receiver The drawings describe the overall placement and height of large components and connectors populated on both sides of the M12M PCB eo e _______ 27 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions 28 Table 3 5 List of Threaded Standoff Suppliers Company Name Part Description Outside Diameter Keystone Electronic Corp Tel 718 956 8900 Fax 718 956 9040 www keyelco com Plain female or 4 40 threaded standoffs available in lengths of 0 125 to 1 0 0 187 round or hex Plain female or M2 5 and M3 0 threaded standoffs available in lengths from 5 to 25 mm 4 5 mm round or hex RAF Electronics Hardware Tel 203 888 2133 Fax 203 888 9860 www rafhdwe com Plain female or 4 40 threaded standoffs available in lengths of 0 125 to 1 0 0 187 round or hex Plain female or M2 5 and M3 0 threaded standoffs available in lengths from 5 to 25 mm 4 5 mm round or hex PEM Engineering and Manufacturing Corp Tel 215 766 8533 Fax 215 766 0143 www pemnet com Self clinching 4 40 female standoffs available in lengths from 0 25 to 1 0 0 165 round
116. ime at Greenwich Meridian Some commonly used versions of universal time follow UTO Universal time as deduced directly from observations of stars and the fixed numerical relationship between universal and sidereal time 3 minutes 56 555 seconds per day UT1 UTO corrected for polar motion UT2 UTO corrected for seasonal variations in the earth s rotational rate UTC Universal time coordinated uniform atomic time system kept very close to UT2 by offsets Maintained by the U S Naval Observatory USNO GPS time is directly related to UTC by the following UTC GPS UTC offset 13 seconds in 2003 User Range Accuracy URA The contribution to the range measurement error from an individual error source apparent clock and ephemeris prediction accuracies converted into range units assuming that the error source is uncorrelated with all other error sources UTM Universal transverse mercator conformal map projection A special case of the transverse mercator projection Abbreviated as the UTM grid it consists of 60 north south zones each six degrees wide in longitude VDOP Vertical dilution of precision See Dilution of Precision Vernal Equinox One of two dates per year when the equator and ecliptic intersect along the line between the earth and sun On these days the day and night are each 12 hours long everywhere on earth hence the term equinox or equal nights The vernal equinox corresponds to the spring equinox in t
117. ing In mobile GPS applications the receiver must be able to track satellites under varying dynamics Vehicle acceleration causes an apparent frequency shift in the received signal due to Doppler shift In order to track signals through acceleration the tracking loops are wide enough to accommodate the maximum expected vehicle acceleration and velocity When the receiver is stationary the tracking loops do not need to be as wide in order to track the satellites In the M12M timing receiver firmware the satellite tracking loops are narrowed once the receiver has acquired the satellites and reached a steady state condition This adaptive approach allows the tracking loops to be narrowed for maximum interference rejection while not unduly compromising the rapid startup and acquisition characteristics of the receiver Test results have demonstrated that this approach is effective at providing an additional 10 dB of jamming immunity to both in band and out of band signals The combined results of the additional filtering and the adaptive tracking loops in the M12M Oncore combine to provide the user with a receiver antenna system effective at improving RF jamming immunity thus making installation in timing applications more flexible and robust The status of the tracking loops wide band or narrow band are indicated by status bits in the Ha and Hb messages Time RAIM Algorithm M12M Timing Receiver Only Time Receiver Autonomous Integrity Monitoring
118. ion of the prime meridian Greenwich with the equator The X and Y vectors rotate with the earth Z is the direction of the spin axis Eccentric Anomaly E The regularizing variable in the two body problem E is related to the mean anomaly M by Kepler s equation M E esin E where e is the eccentricity Eccentricity e The ratio of the distance from the center of an ellipse to its focus to the semi major axis e 1 b2 a2 1 2 where a and b are the semi major and semi minor axes of the ellipse Ecliptic The earth sun orbital plane North is the direction of the system s angular momentum Also called the ecliptic pole Elevation Height above mean sea level or vertical distance above the reference geoid Elevation Mask Angle The elevation angle below which satellites are ignored Normally set to ten degrees to avoid interference problems caused by buildings trees multi path and atmospheric errors Ellipsoid Height The measure of vertical distance above the ellipsoid Not the same as elevation above sea level because the ellipsoid does not agree exactly with the geoid GPS receivers output position fix height referenced to the WGS 84 datum Ephemeris A list of orbital parameters of a celestial object that can be used to compute accurate positions as a function of time Available as broadcast ephemeris or as post processed precise ephemeris Epoch Measurement interval or data frequency For example if measurements are made
119. ional view of the antenna gain pattern for the antenna along a fixed azimuth in a vertical cut is displayed in the following figure The gain pattern clearly indicates that the antenna is designed for full upper hemispherical coverage with the gain diminishing at low elevations This cross section is representative of any vertical cross section over a 0 to 360 degree azimuth range and thus the 3 dimensional gain pattern is a symmetric spheroidal surface It is important to note that this gain pattern varies in elevation angle but not in horizontal azimuth This design is well suited for many GPS applications accommodating full sky coverage above the local horizon and minimizing ground reflected multipath effects RADIATION PATTERN Figure 4 9 Typical Antenna Gain Pattern OOO OOU 63 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Installation Precautions The following precautions should be taken into consideration to avoid the introduction of hazards and adversely affecting performance when installing the GPS Antenna e Mounting bracket must be grounded in accordance with the National Electric Code Section 810 21 e Avoid contact with power lines serious injury could result e Avoid making the antenna the highest point on the roof e Locate the antenna such that there is a 360 view of the sky e Do NOT place any obstructions over or around the antenna e For optimal performa
120. ive remedy THIS WARRANTY IS GIVEN IN LIEU OF ALL OTHER EXPRESS WARRANTIES IMPLIED WARRANTIES INCLUDING WITHOUT LIMITATION IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE LIMITED TO THE DURATION OF THIS LIMITED WARRANTY IN NO EVENT SHALL I LOTUS BE LIABLE FOR DAMAGES IN EXCESS OF THE PURCHASE PRICE OF THE PRODUCT FOR ANY LOSS OF USE LOSS OF TIME INCONVENIENCE COMMERCIAL LOSS LOST PROFITS OR SAVINGS OR OTHER INCIDENTAL SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE INSTALLATION USE OR INABILITY TO USE SUCH PRODUCT TO THE FULL EXTENT SUCH MAY BE DISCLAIMED BY LAW i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Chapter 2 NAVSTAR GPS OVERVIEW CHAPTER SUMMARY Refer to this chapter for the following e Adescription of the NAVSTAR GPS segments e Anexplanation of the GPS navigation message e A list of available public GPS information services i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions ABOUT THE GPS NAVIGATION MESSAGE The NAVigation Satellite Timing and Ranging NAVSTAR Global Positioning System is an all weather radio based satellite navigation system that enables users to accurately determine 3 dimensional position velocity and time worldwide The overall system consists of three major segments the space segment the ground control segment and the user segment Space Segment
121. ix Bit 9 SV on channel 10 used for fix Bit 8 SV on channel 9 used for fix Bit 7 SV on channel 8 used for fix Bit 6 SV on channel 7 used for fix Bit 5 SV on channel 6 used for fix Bit 4 SV on channel 5 used for fix Bit 3 SV on channel 4 used for fix Bit 2 SV on channel 3 used for fix Bit 1 SV on channel 2 used for fix Isb Bit 0 SV on chanel 1 used for fix EEE FE 170 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands For each of twelve channels 12x iepppprrrr i satellite ID 0 37 e ephemeris IODE 0 255 pppp pseudo range 0 4 294 967 295 cm rrrr pseudo range rate 0 4 294 967 295 mm sec Vehicle ID vvvvvv six ASCII character vehicle ID response depends on input command default value is receiver SN C checksum Message length 170 bytes a U O OUO OO UUO ss 171 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank SSS 172 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 12 CHANNEL SELF TEST MESSAGE la The M12M receiver user has the ability to perform an extensive self test The tests that are accomplished during the Self Test are as follows e Antenna connection e RTC communication and time e Temperature sensor e RAM e FLASH ROM e Correlator IC The output of the self test command is
122. k all satellites that are healthy and in the almanac The user can elect to ignore particular satellites in the almanac by using the Satellite Ignore Command In addition the user can restore any previously ignored satellite IDs by issuing a Satellite Ignore Command with the satellite IDs added back to the active list The user may notice a delay between issuing this command and the actual removal or inclusion of particular satellites Default value All satellite SVIDs included Legacy Code Compatibility The Am command has been implemented in an identical fashion on virtually all Oncore receivers 75 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SV IGNORE LIST MESSAGE Am Binary Format Query current SV Ignore List AmxxxxxC lt CR gt lt LF gt where Xxxxx 5 bytes all 0x00 0x2C checksum Message length 12 bytes Complete hex string to query current SV Ignore List 0x40 40 41 6D 00 00 00 00 00 2C 0D 0A Change current SV Ignore List AmkssssC lt CR gt lt LF gt where k 0x00 fixed hex constant ssss 32 bit binary field each bit representing one SVID msb SVID 32 Isb SVID 1 1 Ignore 0 Include C checksum Message length 12 bytes Response Message to either command AmkssssC lt CR gt lt LF gt where k 0x00 fixed hex constant ssss 32 bit binary field each bit representing one SVID msb SVID 32 Isb SVID 1 1 Ignore 0 In
123. l a 3 XTAL d I PIN 1 i 100 1 570 114 2 5 re 9 39 9 2 134 64 2 0 125 3 2 ij Di i gle T ij 5 i Re i 0 225 5 7 M12M Oncore Printed Circuit Board Layout with Straight 0 050 1 27mm Figure 3 4 Pitch 10 Pin Data Header eee 19 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions M12M ONCORE RECEIVER TECHNICAL CHARACTERISTICS Table 3 2 Oncore Technical Characteristics M12M Nav Model General Characteristics Receiver Architecture 12 parallel channel L1 1575 42 MHz C A code 1 023 MHz chip rate Code plus carrier tracking carrier aided tracking Tracking Capability 12 simultaneous satellite vehicles Performance Characteristics Dynamics Velocity 1000 knots 515 m s gt 1000 knots 515 m s at altitudes lt 60 000 ft 18000m Acceleration 4g Jerk 5 m s Vibration 7 7g per Military Standard 810E Acquisition Time Time To First Fix TTFF Tested at 40 to 85 C lt 15 s typical TTFF hot with current almanac position time and ephemeris lt 40 s typical TTFF warm with current almanac position time lt 60 s typical TTFF cold No stored information lt 1 0 s internal reacquisition typical Positioning Accuracy lt 5m 1 sigma lt 10 m 2 sigma Timing Accuracy 1 Pulse Per Second 1 PPS lt 500 ns 2 sigma Datum WGS 84 default One user definable datum
124. le Delay features work the same in 100PPS mode as they do in 1PPS mode In 100PPS mode these commands are used to accurately control the placement of the pulse after the long pulse Mean Time Between Failure MTBF The MTBF for the M12M Oncore family of GPS receivers has been computed using the methods formulas and database of MIL HDBK 217 to be approximately 750 000 hours gt 85 years at 40 C The value has been computed assuming a static application in a benign environment at the given temperature This reliability prediction only provides a broad estimate of the expected random failure rates of the electrical components during the useful life of the product and is not to be used as absolute indications of true field failure rates Receiver Module Installation Your receiver has been carefully inspected and packaged to ensure optimum performance As with any piece of electronic equipment proper installation is essential before you can use the equipment When mounting the M12M receiver board into your housing system special precautions need to be considered Before you install the receiver please review the following Electrostatic Precautions The Oncore Receiver printed circuit boards PCBs contain parts and assemblies sensitive to damage by electrostatic discharge ESD Use ESD precautionary procedures when handling the PCB Grounding wristbands and anti static bags are considered standard equipment in protecting against ESD damage
125. lemented in a similar fashion on the M12 Oncore receivers On eight channel timing receivers such as the VP and UT this information was included in the En T RAIM Setup and Status Message a O UUO Ml 143 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 1PPS CONTROL MESSAGE Gc Binary Format Query current 1PPS Mode GcxC lt CR gt lt LF gt where x 1 hex byte OxFF Checksum 0x24 Message length 8 bytes Complete hex string to query current 1PPS Mode 0x40 40 47 63 24 OD OA Change 1PPS Control Command GcpC lt CR gt LF gt where p 1PPS control 0x00 1PPS disabled 0x01 1PPS on continuously 0x02 1PPS active only when tracking at least one satellite 0x03 1PPS on when T RAIM conditions are met timing receiver only C checksum Message Length 8 bytes Response to above command GcpC lt CR gt LF gt where p 1PPS control 0x00 1PPS disabled 0x01 1PPS on continuously 0x02 pulse active only when tracking at least one satellite 0x03 1PPS on when T RAIM conditions are met timing receiver only C checksum Message Length 8 bytes a 144 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION CONTROL MESSAGE Gd Applicability M12M Positioning and Timing Receivers This message allows the user to choose in which positioning mode the receiver will operate Note that the allowable options are diff
126. lity M12M timing receivers This message allows the user to enable or disable the Time RAIM algorithm Default T RAIM off This command was part of the En message used on 8 channel UT and VP timing receivers 147 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME RAIM SELECT MESSAGE Ge Binary Format Query Current Time RAIM Mode GexC lt CR gt lt LF gt where x one hex byte OxFF C 0xDD Message Length 8 bytes Complete hex string to query current Time RAIM Mode 0x40 40 47 65 FF DD OD 0A Change Current Time RAIM Mode GetC lt CR gt lt LF gt where t mode 0x00 disable 0x01 enable C checksum Message Length 8 bytes Response to either command GetC lt CR gt lt LF gt where t mode 0x00 disable 0x01 enable C checksum Message Length 8 bytes i 148 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME RAIM ALARM MESSAGE Gf Applicability M12M timing receivers This message allows the user to enter the Time RAIM alarm limit in multiples of 100 ns or to query the receiver for the current setting The default alarm limit is 1000 ns Default value 1000 ns This command was part of the En message used on 8 channel UT and VP timing receivers E O Ss ees 149 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands TIME RAIM ALARM MESSAGE
127. load a previously recorded almanac into the M12M s RAM via the serial port The entire almanac data message consists of 34 unique formatted messages that correspond to the subframe and page number of the almanac data see GPS ICD 200 for format description It is not necessary to input an almanac at power up If backup power has been applied the almanac will be retained in RAM If the almanac is not available it will be downloaded from the satellites This can take anywhere from 15 to 30 minutes if satellites are tracked continuously Manually loading an almanac using this command will reduce the TTFF The receiver echoes the input almanac data subframe and page numbers of messages received so the user can validate that each almanac slice has been accepted It is not necessary nor is it recommended to wait for an echo before sending the next data page The M12M receiver will collect an entire almanac in local storage then check the almanac for validity The receiver will update the internal almanac data with the new user supplied almanac upon completion of the receipt of a valid almanac Any single input message that has an invalid subframe i e not 4 or 5 will reset the almanac collection software so that the local collection of almanac data can begin fresh Subframe 5 Page 1 marks the beginning message and resets the collection process The data for Subframe 5 Page 1 must appear first in the string of 34 commands that make up the total almana
128. lution average and the measurement If there is a bad measurement in the set then the average will be skewed and one of the measurements will have a large residual If the magnitude of the residuals exceeds the expected limit then an alarm condition exists and the individual residuals are checked The magnitude of each residual is compared with the size of the expected measurement error If the residual does not fall within a defined confidence level of the measurement accuracy then it is flagged as a blunder Once a blunder is identified then it is removed from the solution and the solution is recomputed and checked again for integrity A simple analogy can be used to demonstrate the concept of blunder detection and removal a table is measured eight times using a tape measure The measurements are recorded in a notebook but one of the measurements is recorded incorrectly The tape measure has 2 mm divisions so the one sigma 10 reading error is about 1 mm This implies that 95 of the measurements should be within 2 mm of truth The measurements and residuals are recorded in the table on the following page From the residual list it is clear that trial six was a blunder With the blunder removed the average and residuals are recomputed This time the residuals fall within the expected measurement accuracy This is shown in Table 3 4 below Table 3 4 Blunder Detection Example Trial Measurement Hesidual Status Ne
129. mand sets all of the GPS receiver parameters to their default values Performance of this utility results in all continuous messages being reset to polled only output and clears the almanac and ephemeris data The time and date stored in the internal real time clock are not changed by the execution of this command Legacy Code Compatibility The Cf command has been implemented in an identical fashion on virtually all Oncore receivers 123 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SET TO DEFAULTS Cf Binary Format Set the GPS receiver to Default values CfC lt CR gt lt LF gt where C 0x25 Message length 7 bytes Complete hex string to Set to Defaults 0x40 40 43 66 25 OD 0A Response to above command CfC lt CR gt lt LF gt where C checksum Message length 7 bytes SSS SSS 124 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands NMEA PROTOCOL SELECT Ci Applicability M12M Positioning Receivers This command causes the M12M positioning receiver to change the serial data format on the primary port from Binary to NMEA 0183 The baud rate of the port is switched from 9600 to 4800 and input commands are recognized in NMEA format only Note that the default mode of all of the NMEA output messages is off To initiate NMEA output the NMEA input commands detailed in the following
130. me shift multiplied by the speed of light is the receiver s measure of the range to the satellite This measurement includes various propagation delays as well as satellite and receiver clock errors Since the measurement is not a true geometric range it is known as a pseudo range The receiver processes these pseudo range measurements along with the received ephemeris data satellite orbit data to determine the user s three dimensional position A minimum of four pseudo range observations are required to mathematically solve for four unknown receiver parameters i e latitude longitude altitude and clock offset If one of these parameters is known altitude for example then only three satellite pseudo range observations are required and thus only three satellites need to be tracked i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions PLANNED CONSTELLATION 21 ACTIVE SATELLITES PLUS 3 SPARES IN 6 ORBITS EACH AT ORBIT 55 DEGREES INCLINATION 4 ORBITS EQUALLY SPACED AROUND EQUATOR SPACE g SEGMENT 4 4 3 DOWNLINK DATA e SATELLITE EPHEMERIS ORBITAL POSITION DATA e SATELLITE CLOCK DATA NAVIGATIONAL L1 L2 SI RANGING CODES UPUNK DATA FANGINGCOI e SATELLITE EPHEMERIS CORRECTIONS e CLOCK CORRECTIONS e CLOCK CORRECTION e PROPAGATION DELAY e VEHICLE EPHEMERIS e VEHICLE HEALTH USER SEGMENT lt ess ZA Seek i MONITOR N t STATIONS AA e lt CONTROL See e
131. mple True Top of second 10 000000000 s 1PPS cable delay correction 0 000654321 s 1PPS offset 0 100000000 s 1PPS rising edge time 10 099345679 s The rising edge of the 1PPS signal is adjusted so that it occurs corresponding to the fractional part of time equal to the total above The fractional part of time is measured relative to UTC or GPS time depending on the setting of the Time Mode OPERATIONAL CONSIDERATIONS When powered on the M12M Oncore Receiver automatically acquires and tracks satellites measures the pseudorange and phase data from each of up to twelve satellites decodes and collects satellite broadcast data computes the receiver s position velocity and time and outputs the results according to the current I O configuration selected by the user eO OUl 43 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Time to First Fix TTFF TTFF is a function of position uncertainty time uncertainty almanac age and ephemeris age as shown in the table below The information shown below in Table 3 8 assumes that the antenna has full view of the sky when turned on Table 3 8 Typical M12M TTFF Information Power up Initial Error Age TIFF TTFF State M12M ae POS TIME ALMANAC EPHEMERIS Timing Hot Hise 3 min 1 month lt 4hrs lt 15s lt 15s 100 f Warm Kri 3 min 1 month Unavailable lt 40s lt 40s Cold f N A N A Unavailable Unavailable
132. nac Status alm N N 105 Message Be Almanac Almanac Data Request almout y y 107 Bf Ephemeris Ephemeris Data Input ephin y y 109 Bh DGPS Pseudorange corout V 111 Correction Request Bj Setup Leap Second Status leapsec y y 113 Bo Time UTC Offset Output utcoff V V 115 Message Bp Receiver Request utcion A J 117 UTC lonospheric Data Cb Almanac Almanac Data Input almin y y 119 EE 70 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands Table 5 1 Input Commands Listed by Binary Command Header continued Binary WinOncore M12M G mimand Function Description Macmonic M12M Timing Page Cc Ephemeris Ephemeris Data Output J N see Bf Ce DGPS Pseudorange Correction Input corin y 121 Cf Receiver Set to Defaults default y 123 Ch Almanac Almanac Data Response _ _ _s N see Cb Ci NMEA Switch I O to NMEA Protocol ioformat y 125 Cj Receiver Receiver ID id y y 127 Ck DGPS Pseudorange Correction Ack N see Ce Co Receiver UTC lonospheric Data Input y y 129 Eq Position ASCII Position Message as8 y y 133 Ga Position Combined Position Message compo y y 137 Gb Time Combined Time Message comtim y V 139 Gc 1PPS 1PPS Control Message ppscon y y 143 Gd Position Position Mode Control M
133. nce do NOT place the antenna inside a building e To prevent ESD damage to the antenna do NOT touch the center pin on the antenna connector e Use only a 50 ohm transmission line when connecting to the antenna e Do NOT apply more than 5 VDC to the center pin of the antenna e f more than one receiver is fed by a single antenna ensure that the receivers are isolated by a high isolation RF splitter Low isolation passive splitters can cause sub optimal performance Antenna Mounting The antenna is installed with a center mounting scheme It uses an industry standard N connector that is incorporated with the post mount bracket The minimum torque to assemble the antenna and custom hex nut on the post mount bracket is 70 kg cm 61 in Ib do not exceed 100 kg cm 86 8 inch lIb It is recommended that an adjustable wrench with a minimum opening of 1 inches be used for this assembly For optimal performance ensure that the base of the antenna is positioned as close as possible to the top of the mounting pole Select a mounting location with a clear view of the sky 360 and use extreme caution when mounting near high voltage power lines It is recommended that the mounting bracket designed specifically for the antenna be used when installing the antenna It can be used to install the antenna to a nominal 1 inch schedule 40 size pipe approximately 1 6 OD The four units included in the mounting assembly are the U bolt post mo
134. nds EPHEMERIS DATA INPUT Bf Applicability M12M positioning and timing receivers This command will cause the receiver to accept satellite ephemeris data input via communications port 1 pin 2 The receiver keeps the ephemerides decoded from all satellites in RAM as long as backup voltage is applied to the receiver and the ephemerides are still valid t te lt 4 hours The input format is identical to the format output by the previous Oncore receivers using the output ephemeris command This allows the same ephemeris output file to be used by the receiver for an ephemeris input file The receiver echoes the input ephemeris data format message so the user can validate the ephemeris data with the new user supplied ephemeris upon completion of the receipt of a valid ephemeris Legacy Compatibility The Bf message was used in an identical manner in virtually all receivers 109 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands EPHEMERIS DATA INPUT Bf Binary Format Input Ephemeris Data Bfi 24x eee C lt CR gt lt LF gt where i SVID 0x01 0x25 eee eee ephemeris subframe sf 1 3 words 3 10 72 bytes per sat format per ICD GPS 200 C checksum Message length 80 bytes Response to above command Cci 24x eee C lt CR gt lt LF gt where i SVID 0x01 0x25 eee eee ephemeris subframe sf 1 3 words 3 10 72 bytes per sat format per ICD GPS 200 C
135. nds between UTC and GPS time If the offset reported by the receiver is zero and UTC is the selected time reference the receiver does not currently have the portion of the almanac that contains the UTC parameters The UTC parameters are broadcast by the satellites as part of the almanac which is repeated every 12 5 minutes The message can be set to output either once polled or any time the UTC offset has been updated or changed from its previous value Default mode Polled Legacy Compatibility The Bo message was used in an identical manner in the UT receiver 115 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands UTC OFFSET OUTPUT MESSAGE Bo Binary Format Request Current UTC Offset BomC lt CR gt lt LF gt where m mode 0 output UTC offset once polled 1 output UTC offset every time it is updated C checksum Message length 8 bytes Response to above command BouC lt CR gt lt LF gt where u UTC offset in seconds 128 127 C checksum Message length 8 bytes i 116 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands REQUEST UTC IONOSPHERIC DATA Bp Applicability M12M Timing and Positioning Receivers This message allows the user to request UTC and ionospheric data decoded from the Navigation Data Message Default mode Polled Legacy Compatibility The Bp message was used in an identical manner in
136. ng applications to increase the timing accuracy and when the receiver is used as a source of differential correction data This command is used to enter the position to be held The position is specified in the same units and referenced to the same datum as the initial position coordinates of latitude longitude and height to the same resolution The height parameter is referenced to the GPS reference ellipsoid Note that all three parameters must be specified The valid ranges of each parameter are the same as those specified in the Combined Position Message Ga Note This command will only be executed if Position Hold is disabled Position Hold is controlled using the Gd message Default values Latitude 0 Equator Longitude 0 Greenwich Meridian Height 0 m GPS Height Legacy Code Compatibility The As command has been implemented in a similar fashion on the older VP and UT UT Oncore receivers EE 93 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION HOLD PARAMETERS As Binary Format Query current Position Hold Parameters ASXXXXXXXXXXXXXC lt CR gt lt LF gt where XXXXXXXXXXXXX 13 out of range hex bytes OxFF C 0xCD Message length 20 bytes Complete hex string to query current Position Hold Parameters 0x40 40 41 73 FF FF FF FF FF FF FF FF FF FF FF FF FF CD 0D 0A Change current Position Hold Parameters AsIllloooohhhhtC lt CR gt lt LF g
137. ngitude 648 000 000 to 648 000 000 milliseconds 180 to 180 degrees hhhh height 100 000 to 1 800 000 cm 1000 to 18 000 m Velocity ss speed 0 51 400 cm sec 0 514 m sec hh heading 0 0 359 9 degrees 0 1 resolution Status rr receiver status msb Bit 15 13 Fix Type 111 3D Fix 110 2D Fix 101 Propagate Mode 100 Position Hold 011 Acquiring Satellites 010 Bad Geometry 001 Reserved 000 Reserved Bit 12 10 Reserved Bit 9 Fast Acquisition Position Bit 8 Filter Reset To Raw GPS Solution Bit 7 Cold Start no almanac almanac out of date or have almanac but time or position unknown Bit 6 Differential Fix Bit 5 Position Lock Bit 4 Auto Survey Mode Bit 3 Insufficient Visible Satellites Bit 2 1 Antenna Sense 00 OK 01 OC 10 UC 11 NV Bit 0 Code Location O EXTERNAL 1 INTERNAL T_T 169 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands INVERSE DIFFERENTIAL WITH PSEUDORANGE OUTPUT Hr Binary Format Geometry dd DOP 0 999 0 1 resolution 0 0 99 9 t Status DOP type Each bit represents one of the following msb Bit 7 antenna undercurrent Bit 6 antenna overcurrent Bit 5 spare Bit 4 spare Bit 3 spare Bit 2 spare Bit 1 spare Isb BitO set HDOP 2D clear PDOP 3D Satellite Stats v number visible 0 12 ff SVs used for fix msb Bits 15 12 not used Bit 11 SV on channel 12 used for fix Bit 10 SV on channel 11 used for f
138. nomalies however isolation and removal of the bad measurement is not possible Once the survey is completed the T RAIM algorithm is capable of error detection isolation and removal Status of the Automatic Site Survey and Position Hold Modes is retained in RAM when the receiver is powered down if battery backup power is provided 100PPS Output M12M Timing Receiver Only With the M12M timing firmware the timing output can be selected between 1PPS and 100PPS This is done using the Pulse Mode command AP See chapter 5 for information on the formatting of this command When selected the 100PPS signal is output on the same pin as the 1PPS and has the same accuracy and stability characteristics as the 1PPS signal Each pulse is approximately 2 3 ms in duration except for every hundredth pulse which is 6 7 ms in duration to allow logic implemented by the user to determine when the top of the second is about to occur The leading edge of the pulse following the long pulse corresponds to the top of the second referenced to UTC or GPS depending on the Time Mode selected by the user using the Aw command Figure 3 6 shows a diagram of the 100PPS output signal GO e OUOU 24 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Top of the UTC GPS second gt 2 3ms 4 gt 6 7ms 100PPS Signal Description Figure 3 6 100PPS Output Waveform The 1PPS Offset and 1PPS Cab
139. nse to above command Eq mm dd yy hh mm ss dd mm mmmm n ddd mm mmmm w shhhh h sss s h m t dd d nn rrrr aa CC lt CR gt lt LF gt where Date mm month 1 12 dd day 1 31 yy year 98 18 full date 1998 2018 UTC Time hh hours 0 23 mm minutes 00 59 ss seconds 00 60 Latitude dd degrees 00 90 mm mmmm minutes 00 59 9999 n direction N North S South Longitude ddd degrees 000 180 mm mmmm minutes 00 59 9999 w direction W West E East 134 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ASCII POSITION MESSAGE Eq Binary Format Response Message Continued Height s sign of height or hhhh h height in meters 1000 0 18 000 0 Velocity sss s speed in knots 000 0 999 9 hhh h heading in degrees 000 0 359 9 Receiver status m fix mode 0 autonomous 1 differential t fix type 0 no fix 1 2D fix 2 3D fix 3 Position Propagate Mode dd d dilution of precision 00 0 99 9 HDOP if 2D PDOP if 3D nn number of satellites in use 00 37 rrrr reference station ID 0000 1023 aa age of differential data in s 00 60 CCC checksum 000 255 Message length 96 bytes Note that unlike all other binary messages the Eq response checksum consists of the three ASCII characters that make up the normal XOR ed checksum of the hex values of the ASCII characters For instance if the hex value of the
140. nt Manufacturer OEM applications M12M receiver offerings include M12M Positioning Receiver The M12M Oncore positioning receiver is a12 channel design offering one of the fastest Time to First Fix TTFF specifications in the industry and split second reacquisition times M12M Timing Receiver The M12M timing receiver is a variant of the M12M positioning receiver and its highly optimized firmware makes it one of the most capable timing receivers on the market Standard features include precise programmable one pulse per second 1PPS or 100 pulse per second 100PPS outputs and features T RAIM integrity monitoring algorithm i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter L Introduction PRODUCT HIGHLIGHTS Features present on all M12M receivers include the following e 12 channel parallel receiver design e Code plus carrier tracking carrier aided tracking e Position filtering e Antenna current sense circuitry e Operation from 2 85 to 3 15 Vdc regulated power e 3V CMOS TTL serial interface to host equipment e 3 dimensional positioning within 25 meters SEP with Selective Availability SA disabled e Latitude longitude height velocity heading time and satellite status information transmitted at user determined rates continuously or polled e Straight 10 pin power data header for low profile flat mounting against host circuit board An optional right angle header is available for vertical PWA
141. nteger part 6 000 000 7 000 000 0x56 Ox8D 0x80 Ox6A OxCF 0xC0 ff fractional part 0 999 0 0 0 999m 0x00 0x03 OxE7 iiffff inverse flattening constant where ii integer part 285 305 0x01 0x1D 0x01 0x31 ffff fractional part 0 999 999 999 0 0 0 999999999 XX delta X 0 1 m 32 768 32 767 3276 8 3276 7 yy delta Y 0 1 m 32 768 32 767 3276 8 3276 7 Zz delta Z 0 1 m 32 768 32 767 3276 8 3276 7 C checksum Message length 25 bytes SE 82 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands RTCM PORT BAUD RATE SELECT COMMAND AO Applicability M12M Positioning receivers This command allows the user to select the baud rate of the RTCM serial input port pin 8 on the 10 pin power data header The allowable baud rates are 2400 4800 and 9600 The baud rate of this secondary port is independent of the status of the primary serial port Default mode 9600 baud Legacy Code Compatibility The AO command structure detailed here is identical to that used on the earlier M12 GT and SL receivers 83 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands RTCM PORT BAUD RATE SELECT COMMAND AO Binary Format Query current RTCM Port Baud Rate AObC lt CR gt lt LF gt where b 1 out of range byte OxFF C 0xF1 Message length 8 bytes Complete hex string to query current RTCM Port Baud Rate 0x
142. o know the vehicle s position relative to a harbor or runway A data link is used to relay the error terms to the moving vessel to allow real time navigation Right Ascension The angular distance measured from the vernal equinox positive to the east along the celestial equator to the ascending node Typically denoted by a capital omega Q Used to discriminate between orbital planes RTCM Radio Technical Commission for Maritime Services Commission set up to define a differential data link to relay GPS correction messages from a monitor station to a field user RTCM SC 104 recommendations define the correction message format and 16 different correction message types SATNAV A local term referring to use of the older TRANSIT system for satellite navigation One major difference between TRANSIT and GPS is that the TRANSIT satellites are in low altitude polar orbits with a 90 minute period Selective Availability SA A DoD program to control the accuracy of pseudorange measurements whereby civilian users receives a false pseudorange which is in error by a controlled amount Differential GPS techniques can reduce these effects for local applications Under SA the DOD guarantees unauthorized users an accuracy of 100m 2DRMS at a 95 confidence level SA was deactivated in May of 2000 resulting in much better accuracies using standard commercial GPS receivers but DoD has the capability to reactivate it at any time Semi major Axis One half
143. ocal zone minutes 0 59 CC checksum er 192 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SWITCH I O FORMAT TO BINARY This utility command switches the serial data format on the primary port from NMEA 0183 to Binary The baud rate of the port is switched from 4800 to 9600 and input commands are recognized in Binary format only SSS O OUO O U nn 193 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SWITCH TO BINARY NMEA 0183 Format Switch to Binary format PMOTG FOR x CC lt CR gt lt LF gt where x format 0 Binary CC optional checksum Note the asterisk is not present unless the optional checksum is present There is no response message to this input command E EEE gt gt gt EE E gt EE E E 194 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank aO OUO se 195 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix APPENDIX 1 GPS Terminology This section provides definition of terms used in the M12M GPS Receiver User s Guide SSS 196 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Almanac Data transmitted by a GPS satellite which includes orbital information on all the satellites clock correction and atmospheric delay parameters These data are us
144. ollowing the message headers contain binary data that can be interpreted as scaled floating point or integer data The field width and appropriate scale factors for each parameter are described in the individual I O message format descriptions Polarity of floating point data is described via two s complement presentation Input commands may also be of the type query current parameter status or enable and disable the output of data or status messages These output status messages include those that the external controller will use for obtaining position velocity time and status data Some care must be exercised in interpreting the command arguments On the following pages it sometimes makes sense to display the command arguments as ASCII characters while in others the hex representation may be a little clearer As mentioned previously the receiver doesn t really care which method is used to generate the messages sent to the receiver so long as the binary strings sent to the receiver meet the specifications Where possible complete hex command strings have been included as examples of what the complete command strings look like Once a basic understanding of the message protocols is developed by the user things will become much clearer Also included in this chapter are message structures for the seven NMEA messages supported by the M12M positioning receiver The NMEA protocol is not supported by the M12M timing receiver The WinOncore12 mn
145. ols data characters without any prefixes will be interpreted as decimal data data beginning with Ox will be interpreted as hex data and data beginning with a lower case b will be interpreted as binary data The native binary data messages used by all Oncore receivers including the M12M consist of a variable number of binary characters hex bytes For ease of use many Oncore users commonly refer to these binary sequences by their ASCII equivalents For instance all binary messages begin with the hex characters 0x40 0x40 which most users convert to the ASCII equivalents e The first two characters after the header comprise the Message ID and identify the particular structure and format of the remaining data e This message data can vary from one byte to over 150 bytes depending on the message being transmitted or received e Immediately following the message data is a single byte checksum which is the Exclusive Or XOR of all bytes after the and before the checksum e The message is terminated with the Carriage Return Line Feed pair OxOD Ox0A Summarizing every binary message has the following components Message Start two hex 0x40 s denote the start of binary message Message ID A Z a z A Z Two ASCII characters the first an ASCII upper case letter followed by an ASCII lowercase or upper case letter These two characters together identify the message type and imply the correct m
146. ommand and the receiver does not contain an almanac the receiver returns one response message with the subframe and page bytes equal to zero Default mode Polled Legacy Code Compatibility The Be command was implemented in an identical fashion on virtually all Oncore receivers E 107 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ALMANAC DATA REQUEST Be RESPONSE IS Cb Binary Format Query Current Almanac Data BemC lt CR gt lt LF gt where m response mode 0x00 Output response message once polled 0x01 Output response message when almanac data changes continuous C checksum Message length 8 bytes Response to above command Cbsp xxx XXX XXX XXX XXX XXX XXX XXX C lt CR gt lt LF gt where sp subframe page subframe 5 pages 1 25 or subframe 4 pages 2 5 7 10 25 Xxx data words words 3 10 each word is 3 bytes long format per ICD GPS 200 C checksum Message length 33 bytes NOTES 1 If an almanac is present in the GPS receiver the receiver outputs all of the almanac pages as shown above Otherwise it returns a Cb output message with all data bytes set to zero 2 The spaces in the response message shown above have been added merely to increase readability There are no embedded spaces in the actual message sent out by the M12M receiver EEE 108 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Comma
147. ommands VEHICLE ID Gk Applicability M12M positioning and timing receivers This message sets or defaults the ID tag By default the ID Tag is the 6 character serial number of the receiver The user may change the ID tag to any combination of six ASCII characters between 0x20 space to 0x7E tilde that may aid in identification of a number of remote sites or vehicles Note that space characters 0x20 may only be used as fillers at the end of the ID tag Any out of range character will also cause the ID tag to remain unchanged An ID tag modified by the user will only be remembered through power cycles if battery back up is provided The ID tag is also output in the 12 channel Position Status Data Message Ha status message Default value Receiver Serial Number Legacy Code Compatibility The Gk command was implemented in a similar fashion on the M12 Oncore receivers 153 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands VEHICLE ID Gk Binary Format Query Current Vehicle ID Tag GkvwvwvwvC lt CR gt lt LF gt where vywvvvv 6 ASCII characters Ox2A in hex C 0x06 Message length 13 bytes Complete hex string to query Current Vehicle ID Tag 0x40 40 47 6B 2A 2A 2A 2A 2A 2A 06 OD OA Change Current Vehicle ID GkvwvwvwvC lt CR gt lt LF gt where vvvvvv 6 ASCII characters 0x2B revert to receiver serial number or vvvvvv 6 ASCII chara
148. one second to compute data from the satellite range measurements Consequently the data that is output 0 to 50 ms after T represents the best estimate of the position velocity and time based on the measurements taken one second in the past at time T 1 Position data latitude longitude and height is computed from the most recent measurement epoch data and is output immediately after the next measurement epoch which is 1 0 to 1 05 seconds after the original measurements were taken saci Soler Satellite Ranges Ty z kt a k Satellite Range Rates T Processor Least Squares PROP SAT Alert Function Position Algorithm Computations _ _ A68ms gt RS 232 Port Output Data ea T 14H vuro te Latitude Ak Ak 4 at k 1 Longitude OkK K 1 at x 4 Frequency offset of receiver local oscillator F 1575 42 MHz Height Hk Hk 1 ear Hk 1 i f K K Conversion from radians s 2 to m s 2 Time Tk Tk 1 1 Alfk Fo K K Conversion from radians s to m s kn 2 4 2475 2 Velocity magnitude wej Ky Ag 1 Ko OK 1 OK 4 Heading HDp tan Ka y 1 K4 x 1 4 quadrant Figure 3 7 Position Status Data Output Message Latency FEE 40 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions To compensate for the one second computational pipeline delay a one second propagated position is compute
149. oning The default value for the vehicle ID will be the receiver s serial number contained in the block of memory containing manufacturing data 167 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands INVERSE DIFFERENTIAL WITH PSEUDORANGE OUTPUT Hr Binary Format Request Current Inverse Differential with Pseudorange Output HrmvwwvwwC lt CR gt lt LF gt where m mode 0 response message output once polled 1 255 response message output at indicated rate continuous 1 once per second 2 once every 2 seconds 3 once every 3 seconds etc vvvvvv vehicle ID six ASCII encoded characters range 20 to 7E inclusive 1 0x2B2B2B2B2B2B2B six ASCII plus characters use receiver SN from manufacturing data 2 Ox2A2A2A2A2A2A six ASCII do not change use last value 3 six other ASCII characters set vehicle ID to those six characters C checksum Message Length 14 bytes Response to above command Hrmdyyhmswwssssaaaaoooohhhhsshhrrdatvfff 12x iepppprrrr vvwvwwvC lt CR gt lt LF gt Date m month 1 12 d day 1 31 yy year 1998 2018 Time h hours 0 23 m minutes 0 59 s seconds 0 60 GPS Time ww GPS week 0 1023 ssss GPS time of week 0 604800 seconds i 168 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands Unfiltered Position aaaa latitude 324 000 000 to 324 000 000 milliseconds 90 to 90 degrees 0000 lo
150. or GPS applications include the following GDOP Geometric DOP three coordinates plus clock offset in the solution PDOP Position DOP three coordinates HDOP Horizontal DOP two horizontal coordinates VDOP Vertical DOP height only TDOP Time DOP clock offset only RDOP Relative DOP normalized to 60 seconds DoD United States Department of Defense The government agency that led the development deployment and operation of GPS Doppler Aiding The use of Doppler carrier phase measurements to smooth the code phase measurements Also referred to as carrier aided smoothing or carrier aided tracking Doppler Shift The apparent change in frequency of a received signal due to the rate of change of the range between the transmitter and receiver See Reconstructed Carrier Phase Double Difference Ambiguity Resolution A method to determine the set of ambiguity values which minimizes the variance of the solution for a receiver pair baseline vector EE 200 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Dynamic Positioning Determination of a timed series of sets of coordinates for a moving receiver each set of coordinates being determined from a single data sample and usually computed in real time Earth Centered Earth Fixed ECEF Usually refers to a coordinate system centered at the center of the earth that rotates with the earth Cartesian coordinate system where the X direction is the intersect
151. or section contains the inverted serial interface Memory Backup Frequently backup batteries are used with M12M receivers Use of a backup battery is not mandatory but can be useful for saving setup information and increasing the speed of satellite acquisition and fix determination when the receiver is powered up after a period of inactivity M12M receivers may be ordered with or without a rechargeable lithium cell onboard use an external backup voltage source or operate without any backup source whatsoever Battery equipped M12M receivers are fitted with 5 mAh cells sufficient for 2 weeks to a month of backup time depending on temperature Note that these cells ARE rechargeable types and in order to charge them the receiver MUST be powered up A factory fresh receiver should be allowed to run for 24 36 hours to provide the battery with an initial full charge Operating With a Backup Source If employed the backup source keeps the RAM and the Real Time Clock RTC in the receiver alive saving setup and status information Time Date Last Calculated Position Almanac and Ephemeris information along with receiver specific parameters and output message configuration are all saved making resumption of operation once main power is restored essentially automatic In this Warm Start scenario the power comes back on the receiver looks to the RTC to see how much time has elapsed since power was removed calculates which satellites should b
152. perating With a Backup Source 13 Operating Without a Backup Source 14 Antenna Drive and Protection Circuitry 15 Active Antenna Configuration 17 M12M Receiver Electrical Connections 17 M12M Nominal Voltage and Current Ranges 18 Main Power 18 Backup Battery Externally applied backup power 18 M12M ONCORE RECEIVER TECHNICAL CHARACTERISTICS 20 M12M TIMING RECEIVER TECHNICAL CHARACTERISTICS 21 RF Jamming Immunity M12M Timing Receiver Only 22 Adaptive Tracking Loops M12M Timing Receiver Only 22 Time RAIM Algorithm M12M Timing Receiver Only 22 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Automatic Site Survey M12M Timing Receiver Only 100PPS Output M12M Timing Receiver Only Mean Time Between Failure MTBF Receiver Module Installation Electrostatic Precautions Electromagnetic Considerations RF Shielding Thermal Considerations Grounding Considerations PCB Mounting Hardware System Integration Interface Protocols Serial Input Output Binary Format Exclusive Or XOR Checksum creation Millisecond to Degree Conversion NMEA Protocol Support NMEA Commands to the Receiver RTCM Differential GPS Support Input Output Processing Time DATA LATENCY Position Data Latency Velocity Data Latency Time Data Latency ONE PULSE PER SECOND 1PPS TIMING Measurement Epoch Timing Output Data Timing Relative To Measurement Epoch 1PPS Cable Delay Correction and 1PPS Offset M12M Timing Receiver Only OPERATIONAL CONSIDERATIONS
153. ponse message Input commands eo U 31 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions may be of the type that changes configuration parameters of the receiver Examples of these input command types include commands to change the initial position receiver internal time and date satellite almanac etc These input commands when received and validated by the receiver change the indicated parameter and result in a response message to show the new value of the parameter that was changed If the new value shows no change then the input command was either formatted improperly or one of the input parameters was out of its valid range NOTE Every change parameter type input command except for the Ci message has a corresponding response message showing the configuration parameter change To request the current status of any current receiver parameter simply enter an input command with at least one parameter out of the normal range The response to properly formatted commands with out of range parameters is to output the original unchanged value of the parameter in the response message Input commands may also be of the type that enable or disable the output of data or status messages These output status messages include those that the external controller will use for measuring position velocity and time Status messages are output at the selected update rate typically once per second for
154. que C A code that provides satellite identification for acquisition and tracking by the user There are several GPS related sites on the World Wide Web that are excellent sources of information about GPS and the current status of the satellites Several are listed below Additional Information Sources U S Coast Guard Navigation Center Civilian GPS service notices general system information and GPS outage reporting http www navcen uscg gov gps default htm U S Naval Observatory USNO time service information and links to USNO timing and other useful sites http tycho usno navy mil NTP Homepage Information on using GPS receivers for precision network timing in both Windows and Linux environments http www ntp org NAVSTAR GPS Homepage General GPS information and links to other useful GPS sites http gps losangeles af mil National Marine Electronics Association NMEA For information on the NMEA protocol specification http www nmea org Radio Technical Commission Marine RTCM For information on the RTCM specification for DGPS corrections http www rtcm org General GPS Information http www gpsworld com gpsworld Helpful equations code snippets and other useful information http www colorado edu geography gcraft notes gps gps_f html z E E EEEEE 10 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions CH
155. r 2 Receiver Descriptions next message to be sent fits around the 800 byte length goal then the message will be output For example if messages totaling 758 bytes are scheduled to be sent and the user requests another 58 byte message then 816 bytes will actually be sent If the user requests yet another 86 byte message then its output will be left pending and will be scheduled when the total number of output bytes allows If backup power is applied during the power off state the polled or continuous option of each output message is stored in the receiver s RAM memory 33 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Exclusive Or XOR Checksum creation In the binary mode a checksum must be included with every command to the receiver Conversely all messages from the receiver include a checksum that may be used to verify the contents of the message An example message is used to illustrate the procedure Command name 12 Channel Position Status Data Output Message Command in Binary format HamC lt CR gt lt LF gt In this message m indicates the response message rate i e 1 once per second 2 once every two seconds etc and C is the checksum In calculating the checksum only the H a and m characters are used The Exclusive Or XOR operation yields a one if only one of the bits is a one Setting m to 1 or 0x01 in hex we have th
156. rd length of 5 meters of cable The thresholds and ranges listed should be considered to have a tolerance of 2 to 3 dB Figure 4 7 below details a typical configuration System Constraints e The gain in decibels is cumulative through all stages i e G G1 G2 G3 The optimal gain of the antenna cabling and any in line amplifiers and splitters for the receiver is between 18 and 36 dB The may operate outside of the optimal gain range but performance will degrade Therefore we do not recommend operating outside of the optimal gain range as indicated above For the system illustrated below the external gain is approximately 24 dB in front of the receiver e System noise F is not to exceed 4dB The cascaded system noise figure formula is f eee Brie 1 9dB for the system shown below where f is the noise figure for stage one and g is the gain for stage one Note that all of the values used in this equation are absolute The resulting number must be converted back to decibels in order ascertain if it is less than 4dB and to compare it with other antenna systems configurations Recall the formula for converting absolute values to decibels and decibels to absolute values 10logf f dB Stage 1 antenna with low noise amplifier LNA g 29cB f 1 8dB Stage 2 5m of RG 174 Cable Stage 3 g 5dB f 5dB M12M Oncore receiver G 85dB f 5 5dB Figure 4 7 Typical System Gain Noise Figure Calculations 5
157. rea or volume enclosed by adjacent lines or surfaces of zero phase of either the carrier beat phase signal or of the difference between two carrier beat phase signals On the earth s surface a line of zero phase is the focus of all points for which the observed value would have an exact integer value for the complete instantaneous phase measurement In three dimensions this lane becomes a surface L Band The radio frequency band extending from 390 MHz nominally to 1550 MHz O UUU 204 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Mean Anomaly M n t T where n is the mean motion t is the time and T is the instant of perigee passage Mean Motion n 2 P where P is the period of revolution Microstrip Antenna A two dimensional flat precisely cut piece of metal foil glued to a substrate Monitor Station Any of a worldwide group of stations used in the GPS control segment to monitor satellite clock and orbital parameters Data collected at these sites are linked to a master station where corrections are calculated and controlled These data are uploaded to each satellite at least once per day from an uplink station Multichannel Receiver A receiver containing many independent channels Such a receiver offers the highest signal to noise ratio SNR because each channel tracks one satellite continuously Multipath Interference similar to ghosts on a television screen which occurs when multiple
158. rface The M12M s serial port operates under interrupt control Incoming commands and data are stored in a buffer that is serviced once a second by the receiver s operating program There is no additional protection or signal conditioning besides the protection designed into the microprocessor since the RxD and TxD pins are connected to the microprocessor directly TxD and RxD are standard inverted serial signals with 3V voltage swings Note THE M12M SERIAL PORTS ARE NOT 5V LOGIC COMPLIANT For input signals minimum input high voltage is 2V and the maximum input high voltage is 3V Minimum input low voltage is 0 V and the maximum input low voltage is 0 8 V For output signals minimum output high voltage is 2 4 V and the maximum output low voltage is 0 5 V This interface is not a conventional RS 232 interface that can be connected directly to a PC serial port an RS 232 driver receiver is required to make this connection The driver receiver provides a voltage shift from the 3V outputs to a positive and negative voltage typically 8V and also has an a l 29 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions inversion process in it Most RS 232 driver receiver integrated circuits Maxim s MAX3232 for example will provide all these functions with only a 3V power supply Binary Format NOTE In the following discussion and in ensuing areas of the manual concerned with communications protoc
159. rity is an Exclusive Or sum of these bits in a word unit A parity error results when a bit or bits is changed during transmission so that the parity calculated at reception is not the same as it was when the message was transmitted Perigee That point in a geocentric orbit when the geometric distance is at a minimum The closest approach of the orbiting body Phase Lock Loop The technique of making the phase of an oscillator signal follow exactly the phase of a reference signal This is accomplished by first comparing the phases of the two signals and then using the resulting phase difference signal to adjust the reference oscillator frequency to eliminate phase difference when the two signals are next compared o e OUUU 206 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Phase Observable See Reconstructed Carrier Phase Point Positioning Geographic positions produced from one receiver in stand alone mode At best position accuracy obtained from a standalone receiver is 15 to 25 meters without SA depending on the geometry of the satellites Polar Motion Motion of the instantaneous axis of the rotation of the earth with respect to the solid body of the earth This motion is irregular but more or less circular with an amplitude of about 15 miles and a main period of about 430 days also called Chandler Wobble Precise Positioning Service PPS The highest level of military dynamic positioning accuracy p
160. rmat Query Current Visible Satellite Data BbmC lt CR gt lt LF gt where m mode 0x00 output response message once polled 0x01 output response message data when visibility data changes approximately once every 5 7 seconds C checksum Message length 8 bytes Response to above command Bbn iddeaas iddeaas iddeas iddeaas iddeaas iddeaas iddeaas iddeaas iddeaas iddeaas iddeaas iddeaas C lt CR gt lt LF gt where n number of visible sats 0 12 For each visible satellite up to n fields contain the following valid data i satellite ID 1 32 dd Doppler in Hz 5000 5000 e elevation in degrees 0 90 aa azimuth in degrees 0 359 s satellite health 0 healthy and not removed 1 unhealthy and removed C checksum Message length 92 bytes NOTE The spaces in the response message shown above have been added merely to increase readability There are no embedded spaces in the actual message sent out by the M12M receiver EEE __________ 104 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ALMANAC STATUS MESSAGE Bd Applicability M12M Timing and Positioning Receivers This command requests almanac status information corresponding to the satellite almanac data currently stored in RAM The GPS receiver continually captures a complete new almanac to internal RAM while tracking satellites If an existing almanac is stored in RAM on power up satellite visibili
161. rofile package and the shielded LNA low noise amplifier offer significantly enhanced performance while operating in a variety of GPS environments Furthermore magnetic and blind hole direct mounting options make the antenna suitable for a number of different installation configurations 52 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Table 4 1 Active Antenna Technical Characteristics GENERAL Antenna Description Passive dielectric patch antenna CHARACTERISTICS Top and bottom radome plastic housing assembly Active low noise amplifier filter PWB assembly RF cable with connector assembly Operating Frequency L1 1575 42 MHz 1 02 MHz PERFORMANCE Input Impedance 50 Ohm CHARACTERISTICS VSWR 1 5 typical 1575 42 MHz 2 5 max Bandwidth 10 to 45 MHz 3cB points Polarization Right hand circular Azimuth Coverage 360 Elevation Coverage 0 to 90 Gain Characteristics of 2 0 dBic minimum at zenith Antenna Element 10 dBic minimum at 0 elevation Filtering 30dB 1675 MHz typical 30dB 1475 MHz typical Antenna Gain 3 Vdc version 24dB typical including 5 dB cable loss Noise Figure lt 1 8dB typical 2 2dB max Dynamics Vibration 7 7 G s Military Standard 810E Shock 100 G s Military Standard 810E ELECTRICAL Power Requirements 3 V 0 2 Vdc for GC3LPxxxxx models CHARACTERISTICS Current Consumption
162. roperly formatted messages are discarded You must take care in correctly formatting the input command Pay particular attention to the number of parameters and their valid ranges An invalid message could be interpreted as a valid unintended message A beginning a valid checksum a terminating carriage return line feed the correct message length and valid parameter ranges are the only indicators of a valid input command to the receiver For multi parameter input commands the receiver will reject the entire command if one of the input parameters is out of range Once the input command is detected the receiver validates the message by checking the checksum byte in the message Input and output data fields contain binary data that can be interpreted as scaled floating point or integer data The field width and appropriate scale factors for each parameter are described in the individual I O message format descriptions Polarity of floating point data positive or negative is described via the two s complement presentation Input command messages can be stacked into the receiver input buffer up to the depth of the message buffer 1200 characters long The receiver will operate on all full messages received during the previous one second interval and will process them in the order they are received Previously scheduled messages may be output before the responses to the new input commands Almost all input commands have a corresponding output res
163. rovided by GPS based on the dual frequency P code and having high anti jam and anti spoof qualities Prime Vertical The vertical circle perpendicular to the celestial meridian PRN Pseudorandom noise a sequence of digital ones and zeros that appear to be randomly distributed like noise but which can be exactly reproduced The most significant property of PRN codes is that they have a low autocorrelation value for all delays or lags except when they are exactly coincident Each NAVSTAR satellite has its own unique C A and P pseudorandom noise codes Pseudolite A ground based GPS transmitter station that broadcasts a signal with a structure similar to that of an actual GPS satellite Pseudolites are designed to improve the accuracy and integrity of GPS particularly near airports Pseudorange A measure of the apparent propagation time from satellite to receiver antenna expressed as a distance A pseudorange is obtained by multiplying the apparent signal propagation time by the speed of light Pseudoranges differ from actual geometric ranges due to the satellite receiver clock offset propagation delays and other errors The apparent propagation time is determined from the time shift required to align correlate a replica of the GPS code generated in the receiver with the received GPS code The time shift is the difference between the time of signal reception measured in the receiver time frame and the time of signal emission measured in th
164. signals arrive at an antenna after having traversed different paths In GPS the signal traversing the longer path will yield a larger pseudorange estimate and increase the error Multiple paths may arise from reflections from structures near the antenna or the ground Multipath Error A positioning error resulting from interference between radio waves that have traveled between the transmitter and the receiver by paths of different electrical lengths Multiplexing Channel A receiver channel that is sequenced through several satellite channels each from a specific satellite and at a specific frequency at a rate which is synchronous with the satellite message bit rate 50 bits per second or 20 milliseconds per bit Thus one complete sequence is completed in a multiple of 20 milliseconds NAD 83 North American Datum 1983 NAVDATA The 1500 bit navigation message broadcast by each satellite at 50 bps on both the L1 and L2 signals The message contains system time clock correction parameters ionospheric delay model parameters and the satellite s ephemeris and health This information is used by the GPS receiver in processing GPS signals to obtain user position velocity and time e O O O O ____ _____ 205 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix NAVSTAR The acronym given to GPS satellites which stands for NAVigation Satellite Timing And Ranging Observation Session The period of time over which
165. t where lll latitude in mas 324 000 000 324 000 000 90 90 0000 longitude in mas 648 000 000 648 000 000 180 180 hhhh height in cm 100000 1 800 000 1 000 00 18 000 00 m t height type 0 GPS height C checksum Message length 20 bytes Response to either command AsIllloooohhhhtC lt CR gt lt LF gt where lll latitude in mas 324 000 000 324 000 000 90 90 0000 longitude in mas 648 000 000 648 000 000 180 180 hhhh height in cm 100000 1 800 000 1 000 00 18 000 00 m t height type 0 GPS height C checksum Message length 20 bytes re 94 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION LOCK SELECT MESSAGE AS Applicability M12M Positioning receivers This message enables or disables the Position Lock function For further details on the Position Lock function refer to the AM command Default mode Disabled Legacy Code Compatibility The AS command was implemented in a similar fashion on the M12 Oncore receiver 95 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION LOCK SELECT MESSAGE AS Binary Format Query current Position Lock Select Status ASxC lt CR gt lt LF gt where x 1 out of range hex byte OxFF C 0xED Message length 8 bytes Complete hex string to query current Position Lock Select Status
166. t Request Current Time RAIM Status HnrC lt CR gt lt LF gt where r output rate 0 polled once 1 255 output at indicated rate 0x01 once per second 0x02 once per every 2 seconds OxFF once per 255 seconds C checksum Message Length 8 bytes Response to above command Hnpysrvwvveensffff repeat sffff for remaining 11channels C lt CR gt lt LF gt where p pulse status 0 off 1 on y 1PPS pulse sync 0 pulse referenced to UTC 1 pulse referenced to GPS time s Time RAIM Solution 0 solution within alarm limits 1 ALARM user specified limit exceeded 2 UNKNOWN due to a alarm threshold set too low b T RAIM turned off c insufficient tracked satellites r Time RAIM status 0 detection and isolation possible 1 detection only possible 2 neither possible vvvV 32 bit field to indicate which svids were removed by T RAIM ee time solution 1o accuracy 0 65535 nsec estimate n negative sawtooth time error 128 127 ns of next pulse For each of 12 channels s satellite id 1 32 ffff fractional GPS local time 0 999999999 ns estimate of satellite C checksum Message Length 78 bytes EEE 166 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands INVERSE DIFFERENTIAL WITH PSEUDORANGE OUTPUT Hr Applicability M12M positioning receivers This message contains information that allows the user to perform inverse differential positi
167. t reference frequency generated in the receiver Carrier Frequency The frequency of the unmodulated fundamental output of a radio transmitter The GPS L1 carrier frequency is 1575 42 MHz Celestial Equator The great circle that is the projection of the earth s geographical equator of rotation onto the celestial sphere Its poles are the north and south celestial poles Celestial Meridian The vertical great circle on the celestial sphere that passes through the celestial poles the astronomical zenith and the nadir Chip The length of time required to transmit either a one or a zero in binary pulse code One chip of the C A code is about 977 ns long which corresponds to a distance of 293m Chip Rate Number of chips per second e g the C A code chip rate 1 023 MHz Clock Offset Constant difference in time readings between two clocks EEE 198 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Appendix Code Division Multiple Access CDMA A method of frequency reuse whereby many radios use the same frequency but with each one having a separate and unique code GPS uses CDMA techniques with Gold codes for their unique cross correlation properties Cold Start Typical time a GPS receiver requires to develop a fix after application of power given that the receiver has no stored data Cold starts times normally have a large standard deviation as the time depends heavily on satellite visibility at any given time Con
168. t messages and a couple of setup steps These are Enabling the desired message strings typically Ha or Hb Bb etc Setting the antenna Mask Angle using the Ag command In the default condition the M12M positioning receiver s mask angle is set at 0 but position accuracy will be improved by setting this angle somewhere in the range of 5 10 This is due to the fact that the ionospheric correction algorithms used by the receiver are less accurate for low lying satellites If NMEA operation is desired this mode should be invoked using the Ci command Once in NMEA mode any of the seven NMEA sentences may be enabled with the appropriate commands as detailed earlier NOTE Once in NMEA mode you will be unable to modify receiver operating parameters such as Mask Angle Satellite Ignore List etc nor will you be able to access any of the receiver diagnostics such as the Self Test or the status bits in the Ha and Hb messages If you wish to use any of these functions you must temporarily switch back to binary mode perform the desired operations and then switch back to NMEA protocol M12M as a Positioning Receiver Using Differential Corrections Setting up the M12M for use as a differential rover is identical to the setup shown above except for a couple of minor additions Disable the ionospheric and tropospheric corrections by invoking mode 0 in the Aq lonospheric Corrections Select Command Having the corrections disa
169. tatus field is V then the time field hhmmss ss will be nulled If the receiver is not computing a position fix sometime after the first fix the time field hhmmss ss will be frozen Legacy Code Compatibility The GPGLL message was output in a similar fashion by VP GT and M12 Oncore receivers Note United States export laws prohibit commercial GPS receivers from outputting valid data if the calculated GPS height is greater than 18 000 meters 11 miles and the calculated 3D velocity is greater than 514 meters second 1135 miles hour If the receiver is used above both of these limits concurrently the height and velocity outputs are clamped to the maximum values In addition the latitude and longitude information will be incorrect EEE 181 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands GPGLL NMEA GEOGRAPHIC LATITUDE LONGITUDE NMEA 0183 Format Set response message rate where PMOTG GLL yyyy CC lt CR gt lt LF gt yyyy update rate 0 9999 seconds CC optional checksum Note the asterisk is not present unless the optional checksum is present Response to above command where GPGLL ddmm mmmm n dddmm mmmm e hhmmss ss a CC lt CR gt lt LF gt ddmm mmmm n latitude dd degrees 00 90 mm mmmm minutes 00 000 59 999 n direction N North S South dddmm mmmm e longitude dd degrees 00 180 mm mmm minutes 00 000 59 999 e direction
170. ted from 5 KV to 15 kV Module not powered stabilized at 45 C is immersed in 18 C water for 20 minutes depth 1 meter Spray 5 NaCl solvent at 35 C Liquid household laundry detergent diluted with water 50 50 Liquid automobile wax Automobile vinyl top cleaner Kerosene Isopropyl Alcohol Sunshine carbon arc system JIS D 0202 Max Voltage 12 Kava Max Capacitance 1000pF 3 transient discharges applied in each polarity to antenna top radome bottom housing and RF connector i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions THIS PAGE INTENTIONALLY LEFT BLANK E OOOO aS 67 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands Chapter 5 1 0 COMMANDS CHAPTER SUMMARY Refer to this chapter for the following e The I O commands supported by the M12M Oncore receiver e Detailed command descriptions SSS 68 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands OVERVIEW The Binary commands can be used to initialize configure control and monitor the M12M receivers The binary commands are supported on the primary communications port at 9600 baud Immediately following this page are listings of the input commands in alphabetical order Command and response structures are detailed on subsequent pages The input and output data fields f
171. that was used for this decision Typical values are between 5 and 10 degrees Depending on the antenna used the receiver is capable of tracking satellites down to the horizon but range and therefore time errors will increase due to atmospheric distortion of the signals from the low satellites Range 0 to 89 degrees Default values M12M Positioning Receiver 0 degrees M12M Timing Receiver 10 degrees Legacy Compatibility The Ag command has been implemented in an identical fashion in virtually all Oncore receivers 73 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SATELLITE MASK ANGLE Ag Binary Format Query current Satellite Mask Angle AgxC lt CR gt lt LF gt where x 1 OxFF hex byte 0xD9 checksum Message length 8 bytes Complete hex string to query the current Satellite Mask Angle 0x40 40 41 67 D9 OD OA Change current Satellite Mask Angle AgdC lt CR gt lt LF gt where d degrees 0 89 degrees 0x00 0x59 C checksum Message length 8 bytes Response to either command AgdC lt CR gt lt LF gt where d degrees 0 89 degrees 0x00 0x59 C checksum Message length 8 bytes SS SES EEE 74 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SATELLITE IGNORE LIST MESSAGE Am Applicability M12M Positioning and M12M Timing receivers The receiver includes in its list of satellites to trac
172. the M12 receiver 117 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands REQUEST UTC IONOSPHERIC DATA Bp Binary Format Request Current UTC lonospheric Data BpmC lt CR gt lt LF gt where m mode 0 output response once polled 1 output response when either UTC or ionospheric data changes C checksum Message length 8 bytes Response to above command CoabcdefghAAAAaaaadtwWnDC lt CR gt lt LF gt where a b c d e f g and h lonospheric Data see ICD GPS 200 Table 20 X for scale factors a a0 128 127 seconds b al1 128 127 seconds semi circle c a2 128 127 seconds semi circle d a3 128 127 seconds semi circle e p0 128 127 seconds f 61 128 127 seconds semi circle g 62 128 127 seconds semi circle h p3 128 127 seconds semi circle AAAA aaaa d t w and W UTC Data see ICD GPS 200 Table 20 IX for scale factors AAAA AO 2 147 483 648 2 147 483 647 seconds aaaa A1 8 388 608 8 388 607 seconds second d Atis 128 127 seconds t tot 0 602 112 seconds w WN 0 255 weeks W WNisr 0 255 weeks n DN 1 7 days D Atise 128 127 seconds C checksum Message length 29 bytes 118 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ALMANAC DATA INPUT Cb Applicability M12M Timing and Positioning Receivers This command allows the user to
173. tion The antenna sense circuit was designed to operate with the Antenna Type and Antenna Type II GPS antennas therefore non quantified antennas may exceed the threshold limits as listed below Under current detect 25 C Good indication greater than 15 mA Undercurrent indication less than 15 mA Over current detect 25 C 80 mA maximum for normal operation NOTE An external power source such as a bias T must be used if the antenna circuit power requirement exceeds the upper limit OOOO ES _ EF_ CSC 15 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions The antenna status information is output in the following I O messages e Ha 12 Channel Position Status Data Message e Hb 12 Channel Short Position Message e la 12 Channel Self Test Message NOTE Detection of an under current situation will not prevent the from operating The will continue to operate normally but will raise the error flag in the three messages indicating a possible antenna problem A chart of the typical output voltage vs the load current is shown below in figure 3 2 Note that there is some drop to the output voltage as higher currents are drawn due to IR losses across the current sense resistor and pass transistor The system engineer should consider this drop if the coax run to the antenna is going to be long and or the gain of the antenna being used is adversely affected by lowered input
174. tive h hour of GMT offset 0 23 m minute of GMT offset 0 59 vvvvvv ID tag 6 characters 0x20 to Ox7e C checksum Message Length 154 bytes Represents UTC time offset from GPS time Offset is rounded to the nearest integer value ES 159 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands This page intentionally left blank EE SSS 160 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands 12 CHANNEL SHORT POSITION MESSAGE Hb Applicability M12M positioning and timing receivers This is a shortened version of the Ha position message provided to the user at a specified update rate Default mode Polled Note United States export laws prohibit commercial GPS receivers from outputting valid data if the calculated GPS height is greater than 18 000 meters 11 miles and the calculated 3D velocity is greater than 514 meters second 1135 miles hour If the receiver is used above both of these limits concurrently the height and velocity outputs are clamped to the maximum values In addition the latitude and longitude information will be incorrect 161 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands SHORT POSITION MESSAGE Hb Binary Format Request Short Position Message HbrC lt CR gt lt LF gt where r output rate 0 output
175. ty information will be available immediately If no almanac data is stored in RAM on power up the receiver will download a new almanac and then compute satellite visibility information Legacy Code Compatibility The Bd command was implemented in an identical fashion on VP Oncore receivers 105 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ALMANAC STATUS MESSAGE Bd Binary Format Query Current Almanac Status BdmC lt CR gt lt LF gt where m mode 0x00 Output status once polled 0x01 Output status when RAM almanac data changes continuous C checksum Message length 8 bytes Response to above command BdvwtassssrrrrrmrrC lt CR gt lt LF gt where v almanac valid flag 0x00 no almanac in receiver 0x01 valid almanac in receiver w almanac week number raw 0x00 0xFF ICD GPS 200 t time of almanac raw 0x00 147 ICD GPS 200 a number of available SVs 0x00 0x20 ssss SVs in almanac 32 bit 2 byte binary field each bit represents one SVID msb SVID 32 1sb SVID 1 rrrrrrrr 8 reserved bytes C checksum Message length 23 bytes i 106 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands ALMANAC DATA REQUEST Be Applicability M12M Timing and Positioning Receivers This command is used to command the M12M to output its current almanac data The user has the option of requesting the almanac data
176. ty message lt 10 ns 1 sigma lt 20 ns 6 sigma Datum WGS 84 default One user definable datum Antenna Antenna Requirements Active antenna module powered by receiver module 80mA max 10dB to 50dB external antenna gain measured at receiver input 3 Vdc or 5 Vdc antenna power provided via header connector Serial Output Messages Latitude longitude height velocity heading time Communication Binary protocol at 9600 baud NMEA 0183 GGA GLL GSA GSV RMC VTG ZDA Software selectable output rate continuous or poll TTL interface 0 to 3 V Electrical Characteristics Power Requirements 2 8 Vdc to 3 3 Vdc 50 mVp p ripple max Keep Alive BATT Power External 2 2 Vdc to 3 2 Vdc 5 uA typical 2 7 Vdc 25 C Power Consumption 155 mW 3 V without antenna Physical Characteristics Dimensions 40 0 x 60 0 x 13 0 mm 1 57 x 2 36 x 0 53 in Weight Receiver 12 5 g Connectors Data power 10 pin 2x5 unshrouded header on 0 050 in centers straight configuration RF right angle MMCX Antenna to Receiver Interconnection Single coaxial cable with power on center conductor to support active antenna Antenna sense circuit Environmental Characteristics Operating Temperature 40 C to 85 C Storage Temperature 40 C to 105 C Humidity 95 over dry bulb range of 38 C to 85 C Altitude 18 000 m 60 000 ft maximum gt 18 000 m 60 000
177. uencies are recommended These cables are typically constructed with a low loss foam dielectric between the center conductor and the outer shield The antenna uses an industry standard female N connector Weatherproof mating N connectors are required to ensure a water resistant seal Some suggested cable connector vendors are e AMP e Amphenol e Huber Suhner ee Te eee ee ee ee ee ee es 65 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions Environmental Tests Provided below is an outline of the product durability and environmental specifications to which the antenna was qualified Durability Validation Tests Type of Test Thermal cycling Cycle Test Temperature Range Thermal Shock Cycle Test Temperature range Humidity Cycle Test Cycling temperature High Temperature Storage Test Low Temperature Storage Test Vibration Test Drop Test Shipping Drop Test ESD Test Immersion Test Salt Spray Chemical Compatibility Ultraviolet Radiation Voltage Transient Test 66 Test Description 600 hours 40 to 85 C 200 hours 40 to 85 C 240 hours 30 to 60 C at 85 R H 85 C 40 C Ref spec MIL STD 810E Method 516 4 procedure IV modified Ref spec MIL STD 810E Method 516 4 procedure IV modified 1 meter drop onto concrete surface 1 meter drop onto concrete surface one corner three edges all six faces Tes
178. unt bracket lock washer and hex nut as illustrated in the following figure Antenna in Extreme Weather and Environmental Conditions To provide additional protection against extreme weather and environmental conditions a length of plastic tubing covering the N connector on the bottom of the antenna is recommended to keep driven rain from directly impinging on the connector mating area This tubing should be secured TT 64 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 4 Antenna Descriptions to the mounting nut of the antenna assembly and should extend several inches past the mating N connectors A product similar to Armstrong s Armaflex Pipe Insulation Tubing products is recommended More information on this product can be found at www armaflex com Use a weather resistant cable tie or clamp to secure the tubing material to the mounting nut Antenna Cable and Connector Requirements The antenna module consumes five volt power diplexed from the interconnecting coaxial cable A 50 ohm coaxial cable is recommended for proper connection of the antenna module to the receiver module Note that for GPS receivers such as the signal attenuation along the cable should not exceed 8 dB at a frequency of 1575 42 MHz the GPS L1 frequency For RG 58 cables the maximum cable length is restricted to approximately 12m to satisfy this 8 dB requirement For long cable runs cables specifically designed for use at microwave freq
179. ventional International Origin CIO Average position of the earth s rotation axis during the years 1900 1905 Correlation Type Channel A GPS receiver channel that uses a delay lock loop DLL to maintain an alignment correlation peak between the replica of the GPS code generated in the receiver and the received code from the satellite Deflection of the Vertical The angle between the normal to the ellipsoid and the vertical true plumb line Since this angle has both a magnitude and a direction it is usually resolved into two components one in the meridian and the other perpendicular to it in the prime vertical Delay Lock Loop The technique whereby the received code generated by the satellite clock is compared with the internal code generated by the receiver clock The latter is shifted in time until the two codes match Delay lock loops can be implemented in several ways including tau dither and early minuslate gating Delta Pseudorange See Reconstructed Carrier Phase Differential Processing GPS measurements can be differenced between receivers satellites and epochs Although many combinations are possible the present convention for differential processing of GPS measurements are to first take differences between receivers single difference then between satellites double difference then between measurement epochs triple difference A single difference measurement between receivers is the instantaneous difference in ph
180. vice ceiling of 60 C 3 Operation at low duty cycles A common example of this type of application is oceanographic buoys These might typically turn on the M12M once a day for a few minutes get a fix and then power the receiver back down Over time the result is that the battery is never allowed to charge up between power cycles and slowly discharges A better choice in this situation is to use an external primary battery with sufficient capacity for the entire deployment or use of a SuperCap or UltraCapacitor as a backup power source Since these can be charged up ina matter of seconds while the receiver is getting it s daily position fix loss of capacity over time is not an issue EEE 14 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Antenna Drive and Protection Circuitry The M12M is capable of detecting the presence of an antenna The receiver utilizes an antenna sense circuit that can detect under current open condition over current shorted or exceeding maximum receiver limits or a valid antenna connection The M12M is designed to provide up to 80 mA of current via the antenna power supply circuit The circuit contains short protection and a means for detecting over current and open circuit conditions of the connection between it and the antenna This allows the user a degree of confidence that the antenna is connected properly and is drawing current This feature c
181. w Residual mm m mm 1 9 998 14 5 OK 2 2 10 001 11 5 OK 1 3 9 999 13 5 OK 4 10 000 12 5 OK 0 5 10 002 10 5 OK 2 6 10 100 87 5 removed 7 9 999 13 5 OK 1 8 10 001 11 5 OK 2 Ave 10 0125 10 000 a UUI 23 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 2 Receiver Descriptions Automatic Site Survey M12M Timing Receiver Only The Automatic Site Survey mode simplifies system installation for static timing applications This automatic position determination algorithm is user initiated and can be deactivated at any time The Automatic Site Survey averages a total of 10 000 slightly over 2 1 2 hours valid 2D and 3D position fixes If the averaging process is interrupted the averaging resumes where it left off when tracking resumes During averaging bit 4 of the receiver status words in the Position Status Data Messages Ha and Hb is set Once the position is surveyed the M12M timing receiver automatically enters the Position Hold Mode At this point the auto survey flag is cleared and the normal position hold flag is set in the receiver status byte of the Ha and Hb messages Once the antenna site has been surveyed in this manner the user can expect a 2D position error of less than 10 meters with 95 confidence and a 3D error of less than 20 meters with 95 confidence Throughout the survey time the T RAIM algorithm if enabled is active and is capable of detecting satellite a
182. where s selection 0x00 both models disabled 0x01 ionospheric model enabled 0x02 tropospheric model enabled 0x03 both models enabled C checksum Message length 8 bytes re 90 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION FILTER SELECT COMMAND AQ Applicability M12M Positioning and Timing receivers This message enables or disables the position filter Default mode Enabled S O UOO eee 91 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION FILTER SELECT COMMAND AQ Binary Format Query current Position Filter Status AQxC lt CR gt lt LF gt where x 1 out of range byte OxFF C OxEF Message length 8 bytes Complete hex string to query current Position Filter Status 0x40 40 41 51 FF EF OD 0A Change current Position Filter Status AQsC lt CR gt lt LF gt where s selection 0x00 disabled 0x01 enabled C checksum Message length 8 bytes Response to either command AQsC lt CR gt lt LF gt where s selection 0x00 disabled 0x01 enabled C checksum Message length 8 bytes eT ee eee eee ee es 92 i Lotus GPS Products M12M User s Guide Revision 1 0 01May06 Chapter 5 I O Commands POSITION HOLD PARAMETERS MESSAGE As Applicability M12M Positioning and Timing receivers The user can specify Position Hold coordinates both for timi

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