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GPS Overview

1. Ece 43 Comparison of Correlator Patterns essere emen 44 Comparison of Multipath Envelopes eseeennemenmene nennen 45 GPS Reference Manual Rev 0l BEST e 1 NovAtel GNSS Antenna Models 2 ccceccceeeeeceeeeeeeeeeeeeeeeeeeeeceeeeeesneeeeesceeeeeenaees 15 2 Comparison of GLONASS and GPS Characteristics c ccccccceeeeeceeeeeeeeeeeeenees 35 3 Typical Receiver TTFF for OEMV Based Products cc ccceeeeeeeeeeeeeeeeeeseeeetees 47 4 Approximate Time and Position Methods sese 48 5 Static Accumulating Materials cc ccceeeeeeeeeeeeceeeeeeaeeeeeeaeeeeecaeeeeesneeeeeeeneeeesennees 57 6 GPS Reference Manual Rev 0l GPS Reference Manual Rev 0l Customer Service Contact your local NovAtel dealer first for more information on products and services To locate a dealer in your area or if your question is not resolved contact NovAtel Inc directly using one of the following methods Call the NovAtel Hotline at 1 800 NOVATEL U S amp Canada or 1 403 295 4900 international Fax 1 403 295 4901 E mail support novatel com Website http www novatel com Write NovAtel Inc Customer Service Department 1120 68 Avenue NE Calgary AB Canada T2E 885 pzmm E MQ EQ M B Try our Knowledge Base at http www n
2. When the carrier phase measurement jumps by an arbitrary number of integer cycles It is generally caused by a break in the signal tracking due to shading or some similar occurrence The process of determining a vessel s approximate position by applying DR from its last known position a vector or a series of consecutive vectors representing the run that has since been made using only the courses being steered and the distance run as determined by log engine rpm or calculations from speed measurements The immediate geographic point of interest to which a vessel is navigating It may be the next waypoint along a route of waypoints or the final destination of a voyage A technique to improve GPS accuracy that uses pseudorange errors at a known location to improve the measurements made by other GPS receivers within the same general geographic area 69 Chapter 15 Dilution of Precision DOP Doppler Doppler Aiding Double Difference Double Difference Carrier Phase Ambiguity Earth Centred Earth Fixed ECEF Eccentricity e Elevation Ellipsoid 70 Glossary A numerical value expressing the confidence factor of the position solution based on current satellite geometry The lower the value the greater the confidence in the solution DOP can be expressed in the following forms GDOP Uncertainty of all parameters latitude longitude height clock offset PDOP Uncertainty of 3 D parameters lati
3. GPS Reference Manual Rev 0l Table of Contents 6 1 5 Search and Rescue Service ssssssssssssssseeeeee 38 6 2 E1E5Eba Receiver oce tie Debet ae Deer pes 38 7 L2C Overview 39 7 1 Application Examlbples 2 dr It ett rre Fei d eem 39 7 2 NovAtel s GNSS Modernization sesssssssssse eene 39 8 L5 Overview 40 9 Multipath 41 9 1 Multipath Basics aesan EE NAN EEE ENEA 42 9 1 1 Pseudorange and Code Chips sse enne 42 9 1 2 Tracking Loops and Correlators sssssssseeeeneees 43 9 2 SUMMA io tec r eoe eec cece tuto dr bri a e tub hir e rcd LM EL ad 46 10 TTFF and Satellite Acquisition 47 10 1 OEMV based Products ter teet atc nete ener detta 47 10 2 SUPERSTAR Il based Products ssssssssseeeeeeen enne 48 11 Standards References 50 12 Unit Conversion 53 1221 DISTANCES a oit tote Noten ete DEG e t stets 53 F22 VOUM nna E 53 12 3 Temperature dee qe ARATE ite ete PUR PE Ret a RETEA 53 42 4 Weight c ende ec Dee ed tei de deae ecu eU aa eae 53 12 5 Hexadecimal Binary and Decimal Equivalents sese 54 12 6 GPS Time Conversions sse eene enne nnne nens 55 12 6 1 GPS Time of Week To Day of Week with Time of Day 55 12 6 2 Calendar Date to GPS Time ssssssssssseeeeeeenn 55 13 Electrostatic Discharge Control ESD Practices 56 ENSIS M M AE 56 13
4. 1 3 2 Static vs Kinematic Positioning ssssssss 1 3 3 Real time vs Post mission Data Processing 1 3 4 Performance Considerations seseeeeeeee 2 SPAN Inertial Navigation Overview 3 Satellite Based Augmentation System 3 1 SBAS Receiver oo eee c cece cee ceccees sees eee eeeeeaueaeeueesseaueeueessesauaneueees 4 L band Positioning 4 1 COVElAGS IE 4 1 1 OmniSTAR Geographic Areas sssssssss 4 1 2 Canada America Wide CDGPS sss 4 2 L band Service Levels ssssssssseeeee 4 2 1 Standard Service sess 4 2 2 High and Extra Performance Services 4 3 L band Commands and Logs sse 5 GLONASS Overview 5 1 GLONASS System Design sssssssssseee 5 1 1 The Control Segment sss 5 1 2 The Space Segment sssssssssssseee 5 1 3 The User Segment sssssssssssseeeeeeetnnes GAMES 5 2 1 GPS Time vs Local Receiver Time susss 5 2 2 GLONASS Time vs Local Receiver Time 5 3 DAUM MEM 6 Galileo NEG ES 6 1 Open Series aee ech ae etn 6 1 2 Commercial Service ceccceeeeceeeeeeeeeceneeeeeeeeeeeeeeeeeeeeees 6 1 3 Safety of Life Service ssssssssssssssseeee 6 1 4 Public Regulated Service ssssssssss
5. EMC EMI EP ESA ESD ESN FAA FCC FDA FDMA FEPROM FIFO FKP FLL FMEA FOC FOG FOM FPGA FR FTP FTS FW GAGAN GaIn GCC GDOP GEO GIC GL GLONASS GM GMS GMT GN GND GNSS G P GP GPAI GPS GRAS Chapter 14 Desired Undesired Eccentricity Early to Late Earth Centred Earth Fixed Electronic Distance Measuring instrument Electrically Erasable Programmable Read Only Memory European Geo Stationary Navigation Overlay System Electronic Industries Alliance Electromagnetic Compatibility Electromagnetic Immunity Engineering Practice European Space Agency Electrostatic Discharge Electronic Serial Number Federal Aviation Administration Federal Communication Commission Frequency Distribution Amplifier Frequency Division Multiple Access Forward Error Correction Flash Erasable Programmable Read Only Memory First In First Out Flachen Korrectur Parameter Plane Correction Parameter German Frequency Lock Loop Failure Mode Effects Analysis Full Operational Capability Fibre Optic Gyro Figure of Merit Field Programmable Gate Array Factory Reset File Transfer Protocol Frequency and Time Standard Firmware GPS Aided GEO Augmented Navigation India Galileo Industries Galileo Control Centre Geometric Dilution Of Precision Geo stationary Satellite GPS Integrity Channel GLONASS NMEA talker ID Global Navigation Satellite System Gauss Markov Ground Mission Segment Greenwich M
6. GPS Reference Manual OM 20000039 Rev 0l Proprietary Notice GPS Reference Manual Publication Number OM 20000039 Revision Level OI Revision Date 2007 07 16 Proprietary Notice No part of this manual may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying and recording for any purpose without the express written permission of a duly authorized representative of NovAtel Inc The information contained within this manual is believed to be true and correct at the time of publication NovAtel MEDLL Narrow Correlator tracking technology ProPak RT 20 and RT 2 are registered trademarks of NovAtel Inc SPAN technology EuroPak GRAFNET GRAFNAV PAC OEMV and Waypoint are trademarks of NovAtel Inc All other brand names are trademarks of their respective holders Copyright 2000 2007 NovAtel Inc All rights reserved Unpublished rights reserved under International copyright laws 2 GPS Reference Manual Rev 0l Table of Contents Proprietary Notice Customer Service 1 GPS Overview 1 1 GPS System Design asii ae r aa i ai 1 1 1 The Space Segment ssssssssssseeee 1 1 2 The Control Segment sss 1 1 3 The User Segment ssssssssssseeeee 1 2 Height Relationships asenn a eiii i 1S GPS Positionllig iiie tere rr rre ette Aas dct 1 3 1 Single Point vs Differential Positioning
7. PZ 90 Receiver Channels Chapter 15 A wide area GPS correction service using L band satellite broadcast frequencies 1525 1560 MHz Data from many widely spaced Reference Stations is used in a proprietary multi site solution OmniSTAR Virtual Base Station VBS types achieve sub meter positioning over most land areas worldwide while OmniSTAR High Performance HP types achieve 10 cm accuracy Use of the OmniSTAR service requires a subscription The starting point of the present navigation leg expressed in latitude and longitude A receiver that monitors four or more satellites simultaneously with independent channels The even or odd quality of the number of ones or zeroes in a binary code Parity is often used to determine the integrity of data especially after transmission The point in a body s orbit at which it is nearest the Earth Precise code or protected code A pseudorandom string of bits that is used by GPS receivers to determine the range to the transmitting GPS satellite P code is replaced by an encrypted Y code when Anti Spoofing is active Y code is intended to be available only to authorized primarily military users See Anti Spoofing C A Code and Y Code Position Dilution of Precision See Dilution of Precision DOP The GPS positioning velocity and time service which is available on a continuous worldwide basis to users authorized by the U S Department of Defence typically u
8. Table 1 NovAtel GNSS Antenna Models Models Frequencies Supported GPS GLONASS 701 511 521 536 537 L1 only Y x 702 532 533 L1 and L2 v x 702L 534 L1 and L2 plus L band Y x 701GGL 538 L1 plus L band Y Y 701GG L1 only 4 4 702GGL L1 and L2 plus L band v 4 702 GG L1 and L2 4 4 GPS Reference Manual Rev 0l 15 Chapter 1 GPS Overview 16 1 3 4 2 Cable Length An appropriate coaxial cable is one that is matched to the impedance of the antenna and receiver being used 50 ohms and whose line loss does not exceed 10 0 dB If the limit is exceeded excessive signal degradation will occur and the receiver may not be able to meet its performance specifications NovAtel offers a variety of coaxial cables to meet your GPS antenna interconnection requirements Note that a conversion is required between the female MMCX connector on a bare OEMV card and the female TNC connector on NovAtel s GNSS antennas Your local NovAtel dealer can advise you about your specific configuration If your application requires the use of cable longer than 30 m refer to the application note RF Equipment Selection and Installation on our website at http www novatel com support applicationnotes htm or you can obtain it directly from NovAtel Customer Service High quality coaxial cables should be used because a mismatch in impedance possible with lower quality cable produces reflections in the cable that increase
9. 27 operational 3 active spares positioned in three circular orbits 23616 km above the Earth and at an inclination of the orbital planes of 56 degrees with reference to the equatorial plane See also Chapter 6 Galileo starting on Page 36 Galn is a consortium of European prime companies charged with the development of the Galileo system for the European Space Agency See Dilution of Precision DOP The shape of the Earth if it were considered as a sea level surface extended continuously through the continents The geoid is an equipotential surface coincident with mean sea level to which at every point the plumb line direction in which gravity acts is perpendicular The geoid affected by local gravity disturbances has an irregular shape GPS Reference Manual Rev 0l 71 Chapter 15 Geodetic Datum Geo stationary Global Navigation Satellite System GLONASS Global Positioning System GPS Great Circle Ground Control Point GRP Handshaking Heading Horizontal Dilution of Precision HDOP Horizontal and Time Dilution of Precision HTDOP Integer Ambiguity Estimates 72 Glossary The reference ellipsoid surface that defines the coordinate system A satellite orbit along the equator that results in a constant fixed position over a particular reference point on the Earth s surface GPS satellites are not geo stationary GLONASS is a radio satellite navigation system the Russian counter
10. 60 72 gyros 19 H handshaking 72 HDOP see dilution of precision heading 69 72 73 76 78 height antenna 41 differential 17 DOP 70 ellipsoid 71 local 73 relationships 11 12 satellite 31 undulation 78 high dynamics 19 horizontal 29 67 69 71 72 77 78 HTDOP see dilution of precision I impedance 16 Inertial Measurement Unit IMU 19 Inertial Navigation System INS 19 initialization 48 in phase I data channel 40 73 Interface Control Document ICD 32 35 50 ionosphere 16 17 20 21 40 67 73 J jamming 42 K kinematic 15 41 43 73 76 L L2C 10 39 GPS Reference Manual Rev 0l Index L5 frequency 10 40 73 lane 73 78 latitude and longitude 9 70 L band 10 27 28 73 line loss 15 line of site 19 41 local gravity 71 multipath 46 NovAtel dealer 16 50 region 11 17 73 78 tangent plane 73 time 17 33 74 logs and commands 21 28 47 loss of lock 48 68 low latency solution 73 M magnetic 67 69 72 74 mask angle 74 master control station 10 68 matched 16 74 mean sea level 9 11 12 63 71 meridian 69 70 74 misclosure 76 Mobile Satellite MSAT 25 mode navigation 48 modulated 10 21 39 40 42 68 MSAS Japanese SBAS 20 multipath 15 17 41 42 46 74 N navigation 3 D 77 ephemeris 71 gps overview 9 mode 48 satellite system 60 NAVSTAR GPS satellites 9 10 39 40 72 73 N
11. International Geometric Reference Field International GPS Service Central Bureau IGS CB Intermodulation Integrated Multipath Limiting Antenna International Maritime Organization Inertial Measuring Unit Inhibit Inertial Navigation System Input Output Issue of Data Ephemeris In Orbit Validation Internet Protocol Interrupt Request IF Signal Generator International Organization for Standardization not an acronym but a short form International Terrestrial Reference System Jet Propulsion Laboratory NASA Joint Test Action Group Klystron Power Amplifier Kilobit GPS Reference Manual Rev 0l Acronyms mBOC MEDLL MEO MET MET MGRS MHz MIB MIL MINOS MKI MKMF MMCX MMT MOPS MP MPC MPM ms MSAS MSAT MSB MSL MSR MTBF MTSAT N A Chapter 14 Kilobyte Key Management Facility The 1575 42 MHz GPS carrier frequency including C A and P Code Future GPS L1 civilian frequency Future Galileo L1 civilian frequency The 1227 60 MHz 2nd GPS carrier frequency P Code only The L2 civilian code transmitted at the L2 frequency 1227 6 MHz The 1176 45 MHz 3rd civil GPS frequency that tracks carrier at low signal to noise ratios Local Area Augmentation System Liquid Crystal Display Light Emitting Diode Line Feed LAAS Ground Facility Left Hand Circular Polarization Line Maintenance Equipment Low Noise Amplifier Local Oscillator Line Replacement Unit Least significant bit Low Voltage Transistor Tr
12. The GLONASS control segment similar to GPS must monitor the status of satellites determine the ephemerides and satellite clock offsets with respect to GLONASS time and UTC Coordinated Universal Time and twice a day upload the navigation data to the satellites 5 1 2 The Space Segment The Space Segment is the portion of the GLONASS system that is located in space that is the GLONASS satellites that provide GLONASS ranging information When complete this segment will consist of 24 satellites in three orbital planes with eight satellites per plane Figure 11 View of GPS and GLONASS Satellite Orbit Arrangement on Page 31 shows a combined GPS and GLONASS satellite system 5 1 3 The User Segment 30 The User Segment consists of equipment such as a NovAtel OEMV family receiver that tracks and receives the satellite signals This equipment must be capable of simultaneously processing the signals from a minimum of four satellites to obtain accurate position velocity and timing measurements Like GPS GLONASS is a dual military civilian use system The system s potential civil applications are many and mirror those of GPS GPS Reference Manual Rev 0l GLONASS Overview Chapter 5 Figure 11 View of GPS and GLONASS Satellite Orbit Arrangement Following are points about the GLONASS space segment The geometry repeats about once every 8 days The orbit period of each satellite is approximately 8 17 of a sider
13. e A relative humidity level must be maintained between 20 and 80 non condensing e No ESD sensitive board or component should be removed from its protective package except in a static controlled location e Astatic controlled environment and correct static control procedures are required at both repair stations and maintenance areas e ESD sensitive devices must be handled only after personnel have grounded themselves via wrist straps and mats Boards or components should never come in contact with clothing because normal grounding cannot dissipate static charges on fabrics e A circuit board must be placed into an anti static plastic clamshell before being removed from the work location and must remain in the clamshell until it arrives at a static controlled repair test center e Circuit boards must not be changed or moved needlessly Handles may be provided on circuit boards for use in their removal and replacement care should be taken to avoid contact with the connectors and components e On site repair of ESD sensitive equipment should not be undertaken except to restore service in an emergency where spare boards are not available Under these circumstances repair station techniques must be observed Under normal circumstances a faulty or suspect circuit board must be sent to a repair center having complete facilities or to the manufacturer for exchange or repair GPS Reference Manual Rev 0l Electrostatic Discharge Cont
14. highly secure government encryption scheme To enhance availability the PRS service is intended to have anti jamming and anti spoofing capabilities The PRS will be transmitted in two frequency bands L1 at 1575 42 MHz and E6 at 1278 75 MHz Users may receive signals from the two frequency bands independently 6 1 5 Search and Rescue Service 6 2 38 A specific public service designed to assist in search and rescue operations will make it possible to locate person and vehicles in distress The vehicles will be fitted with beacons which having been activated in the event of an emergency will send an alerting signal to the rescue centre The Galileo Programme provides this search and rescue service for users based on humanitarian and public service principles of the international COSPAS SARSAT system while at the same time making search and rescue operations more effective L1L5E5a Receiver NovAtel s L1L5E5a receiver offers superior 16 channel tracking of GPS L1 L5 Galileo L1 E5a and SBAS signals in a Euro form factor card packaged in the popular EuroPak enclosure e Tracks and decodes GPS L1 and L5 SBAS L1 and L5 and Galileo L1 and E5a e Digital Pulse Blanking on GPS L1 and L5 and Galileo L1 and E5a for radar and pulsed DME interference mitigation e Includes L1 GPS RFI improvements as developed for the US WAAS reference receivers e External OXCO input and enclosure option with internal OCXO See also Section 7 2 NovAtel s
15. 17 67 beam L band 24 25 bearing 68 73 76 78 GPS Reference Manual Rev 0l blocked satellites 19 29 74 broadcast bandwidth 44 base station 10 ephemeris 16 47 68 GEO 21 L band 24 25 73 75 time 33 34 buffer 72 C C A code 10 42 46 77 canyon 29 48 carrier phase 10 17 29 35 39 43 67 71 73 78 C Band 22 68 CDGPS 23 28 68 certified 20 channels 31 40 70 75 77 checksum 68 74 chip code 42 44 68 choke ring 46 circuit board 58 circular error probable CEP 45 68 clock atomic 32 bias 14 42 75 data 10 drift 70 error 16 33 errors 42 frequency 35 GLONASS 34 L2C 39 offset 33 70 code chip 42 44 68 code division multiple access CDMA 35 40 code phase 21 43 76 commands and logs 21 25 28 34 47 communication 28 31 68 72 constellation 10 72 79 Index 80 control segment 30 controller area network bus CAN Bus 60 conversion 12 53 67 Coordinated Universal Time UTC 34 69 coordinates 13 25 34 48 73 copyright 2 correlators 41 46 course 67 69 72 76 cross correlation 40 76 cycle 67 69 cyclic redundancy check CRC 71 D data link 14 datum 25 34 35 72 dead reckoning DR 69 delay lock loop 43 destination 69 76 differential positioning baselines 17 GLONASS 20 GPS 69 L band 23 27 28 multipath 41 46 overview 13 SBAS 21 22 setup 14 76 SPAN 19 standards 50 76 di
16. 73 Chapter 15 Magnetic Variation Mask Angle Matched Observation Set Pair Measurement Error Variance Measurement Time Epoch Misclosure Multipath Errors Nanosecond Non Volatile Memory Null Field Obscuration Observation Observation Set 74 Glossary The angle between the magnetic and geographic meridians at any place expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north The minimum GPS satellite elevation angle permitted by a particular receiver design Satellites below this angle will not be used in position solution Observations from both the base station and the local receiver which have been matched by time epoch contain the same satellites and are corrected for any known offsets The square of the standard deviation of a measurement quantity The standard deviation is representative of the error typically expected in a measured value of that quantity The point in time at which a receiver takes a measurement The gap between a receiver s computed and actual position GNSS positioning errors caused by the interaction of the satellite signal and its reflections 1 x 10 second A type of memory device that retains data in the absence of a power supply By NMEA standard indicates that data is not available for the field Indicated by two ASCII commas for example HEX 2C2C or for the last data field in a sentence one com
17. BIH Defined Conventional Terrestrial System CTS or BTS 1984 0 Figure 4 The WGS84 ECEF Coordinate System In differential positioning also known as relative positioning the coordinates of a GPS receiver at an unknown point the rover station are sought with respect to a GPS receiver at a known point the base station The concept is illustrated in Figure 5 Example Differential Positioning Setup on Page 14 The differential position accuracy of two receivers locked on the same satellites and not far GPS Reference Manual Rev 0l 13 Chapter 1 GPS Overview 14 removed from each other up to tens of kilometers is extremely high The largest error contributors in single point positioning are those associated with atmospheric induced effects These errors however are highly correlated for adjacent receivers and hence cancel out in differential measurements Since the position of the base station can be determined to a high degree of accuracy using conventional surveying techniques any differences between its known position and the position computed using GPS techniques can be attributed to various components of error as well as the receiver s clock bias Once the estimated clock bias is removed the remaining error on each pseudorange can be determined The base station sends information about each satellite to the rover station which in turn can determine its position much more exactly than would be possible otherwise The advan
18. Flash Configuration Parameters International Special Committee On Radio Interference Clock Status Card Long Code System Clock Moderate Length Code Course Made Good Comparator Message Processor Compact Measurement Record Post Correlation Carrier to Noise Ratio in dB Hz Coordinating Committee on Multilateral Export Controls Course Over Ground Coordinate Geometry Cosmitscheskaja Sistema Poiska Awarinitsch Sudow Russian space system for search of vessels in distress Complex Programmable Logic Device Central Processing Unit Carriage Return Cyclic Redundancy Check Common Reference Receiver Commercial Service Canada Shipping Act Coordination Scientific Information Center Conventional Terrestrial Pole Clear To Send Conventional Terrestrial System Continuous Wave Decibel Decibel Relative to 1 milli Watt Direct Current Data Carrier Detected Data Communications Equipment Modem Digitally Controlled Oscillator Direct Digital Sampling Differential Global Navigation Satellite System Differential Global Positioning System Dynamic Host Configuration Protocol Data Logger Delay Lock Loop Department of Defence U S Dilution Of Precision Digital Pulse Blanking Dead Reckoning Dynamic Random Access Memory Distance Root Mean Square Digital Signal Processor Data Set Ready Data Terminal Equipment Data Terminal Ready GPS Reference Manual Rev 0l Acronyms D U e E L ECEF EDM EEPROM EGNOS EIA
19. GNSS Modernization on Page 39 GPS Reference Manual Rev 0l Chapter 7 L2C Overview 7 1 7 2 Currently Block IIIA and Block IIR NAVSTAR GPS satellites transmit the civilian C A code on the L1 frequency and the military P Y code on both the L1 and L2 frequencies The new Block IIR M satellites will transmit the same signals as the previous two blocks but will also have a new signal called L2C on the L2 frequency L2 has a carrier frequency of 1227 60 MHz L2C has two codes the moderate length code CM and the long code CL The CM code carries data while the CL is the pilot signal The CM code is 10 230 chips long and repeats every 20 milliseconds It is bi phase modulated with message data The CL code is 767 250 chips long and repeats every 1 5 seconds Since L2 is shared between civil and military signals L2C is limited to a single bi phase component in quadrature with the P Y code Even with L2C limited to a 1 023 MHz clock rate to maintain spectral separation from the military M code there is an important advantage in having two codes The advantage stems from the fact that L2C time multiplexes two codes of different length The CM is bi phase modulated with data and the CL has no data modulation The composite signal is clocked at 1 023 MEZ and alternates between chips of each code The L2C and L1 C A codes ensure that there are always two accessible civilian codes Application Examples Here are a few of the many d
20. Geodetic Survey of Canada see Chapter 11 Standards References starting on Page 50 Why is this important for GPS users The above formula is critical for GPS users as they typically obtain ellipsoid heights and need to convert these into mean sea level heights Once this conversion is complete users can relate their GPS derived heights to more usable mean sea level heights GPS Positioning GPS positioning can be categorized as follows l single point or differential 2 static or kinematic 3 real time or post mission data processing A distinction should be made between accuracy and precision Accuracy refers to how close an estimate or measurement is to the true but unknown value precision refers to how close an estimate is to the mean average estimate Figure 3 illustrates various relationships between these two parameters the true value is located at the intersection of the cross hairs the centre of the shaded area is the location of the mean estimate and the radius of the shaded area is a measure of the uncertainty contained in the estimate High acar acy Levy eC a high precision high precision High accuracy Lovey eur ey low precision lva precizion Figure 3 Accuracy versus Precision 1 Environment Canada 1993 Guideline for the Application of GPS Positioning p 22 Minister of Supply and Services Canada GPS Reference Manual Rev 0l GPS Overview Chapter 1 1 3 1 Single Point vs Dif
21. Lane World Geodetic System 1984 WGS84 Y Code 78 Glossary NovAtel s Waypoint Software This is a point with no tie or control information It might have two stations connected to it but one is pointing to it and the other is pointing from it Bearing relative to true north compass bearing corrected for compass error Heading relative to true north The number of hours per day with three or more satellites visible Three visible satellites can be used to determine location if the GPS receiver is designed to accept an external altitude input Navigation mode in which a fixed value of altitude is used for one or more position calculations while horizontal 2D position can vary freely based on satellite range measurements The distance of the geoid above positive or below negative the mathematical reference ellipsoid spheroid Also known as geoidal separation geoidal undulation geoidal height The GPS receiver specification which indicates the solution rate provided by the receiver when operating normally See Coordinated Universal Time Vertical Dilution of Precision See Dilution of Precision DOP By NMEA standards a data field which may or may not contain a decimal point and which may vary in precision following the decimal point depending on the requirements and the accuracy of the measuring device A reference point on a track A particular integer ambiguity value on one carrier phase range me
22. in the order of 1 8 m CEP using a consumer grade wide correlator However the benefits of PAC technology become most significant during pseudorange DGPS operation where the GNSS system biases are largely removed Receivers operating DGPS low multipath environment and using a choke ring ground plane or GPS 700 family antenna with NovAtel s Narrow Correlator tracking technology receivers are able to achieve accuracies in the order of 0 75 m CEP NovAtel s PAC technology receivers are able to achieve accuracies in the range of 0 35 to 0 5 m CEP PAC technology achieves this higher accuracy through a combination of low noise ranging measurements and a very narrow correlation window that dramatically reduces the effects of multipath interference and distortion Consumer Grade Wide Correlator Narrow Correlator tracking technology Pseudorange Error m eo 10m 50m 90m Multipath Delay m 290m 440m Figure 19 Comparison of Multipath Envelopes GPS Reference Manual Rev 0l 45 Chapter 9 Multipath 9 2 Summary 46 Any localized propagation delays or multipath signal reception cause biases to the GNSS ranging measurements that cannot be differenced by traditional DGPS single or double differencing techniques Multipath is recognized as one of the greatest sources of errors encountered by a system operating in single point or differential
23. is achieved the Galileo navigation signals will provide a good coverage even at latitudes up to 75 degrees north which corresponds to the North Cape and beyond The large number of satellites together with the optimisation of the constellation and the availability of the three active spare satellites will ensure that the loss of one satellite has no discernible effect on the user Two Galileo Control Centres GCC will be implemented on European ground to provide for the control of the satellites and to perform the navigation mission management The data provided by a global network of twenty Galileo Sensor Stations GSS will be sent to the Galileo Control Centres through a redundant communications network The GCC s will use the data of the Sensor Stations to compute the integrity information and to synchronize the time signal of all satellites and of the ground station clocks The exchange of the data between the Control Centres and the satellites will be performed through so called up link stations Five S band up link stations and 10 C band up link stations will be installed around the globe for this purpose As a further feature Galileo will provide a global Search and Rescue SAR function based on the operational search and rescue satellite aided tracking Cospas Sarsat system To do so each satellite 1 Galileo Overview information from ESA Navigation website http www esa int esaCP index html GPS Reference Manual Rev 0l G
24. published broadcast protocol l If the coordinates are output using the CSRS datum Refer to the DATUM command in the OEMV Family Firmware Reference Manual 2 The Geological Survey of Canada website is at http gsc nrcan gc ca index e php GPS Reference Manual Rev 0l 25 Chapter 4 L band Positioning 4 1 2 1 CDGPS Coverage Figure 10 CDGPS Percentage 96 Coverage Map as of June 6 2007 below is a conservative map of the coverage areas that CDGPS guarantees The coverage may be better in your area 9D 95 100 Figure 10 CDGPS Percentage 96 Coverage Map as of June 6 2007 In Figure 10 10096 coverage means that a correction is received for every visible satellite at or above 10 degrees 90 coverage means that a correction is received for 90 of visible satellites For example if a user views 10 satellites but has 9096 coverage then there are no corrections available for one of the satellites In that case our firmware shows that a correction is missing for that SV and excludes it from the position calculation 4 1 2 2 Performance For the OEMV Family CDGPS position accuracy is 0 7 m circular error probable CEP Refer also to the Performance section of the Technical Specifications appendix in the OEMV Family Installation and Operation User Manual 1 Please see Page 52 for CDGPS contact information 2 CEP The radius of a circle such that 5096 of a set of events occur inside the boundary 26 GPS Reference
25. starting on Page 39 The third civil GPS frequency at 1176 45 MHz beginning with the first Block IIF NAVSTAR GPS satellite to be launched in 2007 This frequency is located within the 960 1215 MHz frequency band The L5 signal is equally split between an in phase I data channel and a quadrature Q data free channel which improves resistance to interference especially from pulse emitting systems in the same band as LS See also Chapter 8 L5 Overview starting on Page 40 A particular discrete ambiguity value on one carrier phase range measurement or double difference carrier phase observation The type of measurement is not specified L1 L2 L1 L2 iono free An observation set as described on Page 74 taken by the receiver on which the software is operating A coordinate system based on a plane tangent to the ellipsoid s surface at the Plane user s location The three coordinates are east north and up Latitude longitude and height positions operate in this coordinate system A position solution which is based on a prediction A model based on previous base station observations is used to estimate what the observations will be at a given time epoch These estimated base station observations are combined with actual measurements taken at the rover station to provide a position solution Bearing relative to magnetic north compass bearing corrected for deviation Heading relative to magnetic north GPS Reference Manual Rev 0l
26. zero value that is all heights are referenced to this surface What is an ellipsoid An ellipsoid also known as a spheroid is a mathematical surface which is sometimes used to represent the Earth Whenever you see latitudes and longitudes describing the location this coordinate is being referenced to a specific ellipsoid GPS positions are referred to an ellipsoid known as WGS84 or WGS 84 World Geodetic System of 1984 What is the relationship between a geoid and an ellipsoid The relationship between a geoid and an ellipsoid is shown in Figure 2 Illustration of Receiver Height Measurements on Page 11 References 1 Topography 2 Geoid mean sea level 3 Spheroid ellipsoid H Receiver computed height above below geoid N Geoidal Height undulation h GPS system computed height above the spheroid N h H Figure 2 Illustration of Receiver Height Measurements From the above diagram and the formula h H N to convert heights between the ellipsoid and geoid we require the geoid ellipsoid separation value This value is not easy to determine A world wide model is generally used to provide these values NovAtel GPS receivers store this value internally This model can also be augmented with local height and gravity information A more GPS Reference Manual Rev 0l 11 Chapter 1 GPS Overview 1 3 12 precise geoid model is available from government survey agencies for example U S National Geodetic Survey or
27. 0 wavelength 78 waypoint 69 75 76 78 Waypoint Products Group 15 29 website 8 50 51 WGS84 11 13 34 35 78 wide area 20 21 25 27 wide lane 78 X XYZ system 13 70 Y yaw 69 72 Y code 67 75 78 83 rN Nolte OM 20000039 Rev Ol 2007 07 16
28. 07 714285 weeks 5 days 432 000 seconds 48 600 seconds 480 600 seconds 55 lcm Electrostatic Discharge Control ESD Practices 13 1 Overview Static electricity is electrical charge stored in an electromagnetic field or on an insulating body This charge can flow as soon as a low impedance path to ground is established Static sensitive units can be permanently damaged by static discharge potentials of as little as 40 volts Charges carried by the human body which can be thousands of times higher than this 40 V threshold can accumulate through as simple a mechanism as walking across non conducting floor coverings such as carpet or tile These charges may be stored on clothing especially when the ambient air is dry through friction between the body and or various clothing layers Synthetic materials accumulate higher charges than natural fibers Electrostatic voltage levels on insulators may be very high in the order of thousands of volts Various electrical and electronic components are vulnerable to electrostatic discharge ESD These include discrete components hybrid devices integrated circuits ICs and printed circuit boards PCBs assembled with these devices 13 2 Handling ESD Sensitive Devices 56 ESD sensitive devices must only be handled in static controlled locations Some recommendations for such handling practices follow e Handling areas must be equipped with a grounded table floor mats and wrist strap
29. 110 38 111011 59 1010000 80 10010 18 100111 39 111100 60 1010001 81 10011 19 101000 40 111101 61 1010010 82 10100 20 101001 41 111110 62 1010011 83 10101 21 101010 42 111111 63 1010100 84 10110 22 101011 43 1000000 64 1010101 85 10111 23 101100 44 1000001 65 1010110 86 11000 24 101101 45 1000010 66 1010111 87 11001 25 101110 46 1000011 67 1011000 88 11010 26 101111 47 1000100 68 1011001 89 11011 27 110000 48 1000101 69 1011010 90 11100 28 110001 49 1000110 70 1011011 91 11101 29 110010 50 1000111 71 1011100 92 11110 30 110011 51 1001000 72 1011101 93 11111 31 110100 52 1001001 73 1011110 94 100000 32 110101 53 1001010 74 1011111 95 100001 33 110110 54 1001011 75 1100000 96 100010 34 110111 55 1001100 76 1100001 97 100011 35 111000 56 1001101 77 1100010 98 100100 36 111001 57 1001110 78 1100011 99 1100100 100 a These binary to decimal equivalents only go up to decimal 100 for the purpose of example Please use a calculator for other conversions 54 GPS Reference Manual Rev 0l Unit Conversion 12 6 GPS Time Conversions Chapter 12 The following sections provided examples for converting to and from GPS Time 12 6 1 GPS Time of Week To Day of Week with Time of Day The value given for GPS Time of Week represents the number of seconds into the week Therefore to determine the day and time from that value calculations are performed to break down the number of seconds into day hour minute and second values For example s
30. 2 Handling ESD Sensitive Devices sss 56 13 3 Prime Static Accumulators ssssssssssssseeeee ennemis 57 13 4 Handling Printed Circuit Boards sssssssseeeee enne 58 14 Acronyms 59 15 Glossary 67 4 GPS Reference Manual Rev 0l o o 100iAcnD NAVSTAR Satellite Orbit Arrangement seen 9 Illustration of Receiver Height Measurements see 11 Accuracy versus Precision eese eee 12 The WGS84 ECEF Coordinate System sse 13 Example Differential Positioning Setup seeeeennennen ene 14 SBAS atnid NovAtel e e eee Ere Rr ue RD PUE 20 The SBAS Concept x engCRRPRBOC ER AER e ERO Cn 22 L band Concept 3 os epe erred 23 CDGPS Frequency Beams eese nennen nnnm nennen nnne 25 CDGPS Percentage 96 Coverage Map as of June 6 2007 suse 26 View of GPS and GLONASS Satellite Orbit Arrangement sees 31 GPS and GLONASS L1 Frequencies seen 32 GLONASS Antipodal Satellites eeeeeeseeeeeennenm nmn 33 GNSS Signal Multipath vs Increased Antenna Height eeeeee 41 Multipathy 2 52 uu nii ete nto nel e Ie et iuba aee tee Dara we Do e i eic els 42 Time Delay 2 see neu inei ee tet iq euet iei uera ett ier ue sake felt iu eoe oor is 43 G A Code Distortion EEEIDIP
31. ASS and GPS Characteristics Parameter Detail GLONASS GPS Satellites Number of satellites 21 3 spares 21 3 spares Number of orbital planes 3 6 Orbital plane inclination degrees 64 8 55 Orbital radius kilometers 25 510 26 560 Signals Fundamental clock frequency MHz 5 0 10 23 Signal separation technique b FDMA CDMA Carrier frequencies MHz L1 1598 0625 1609 3125 1575 42 L2 1242 9375 1251 6875 1227 6 Code clock rate MHz C A 0 511 1 023 P 5 11 10 23 Code length chips C A 511 1 023 P 5 11 x 10 6 187104 x 10 C A code Navigation Superframe duration minutes 2 5 12 5 Message Superframe capacity bits 7 500 37 500 Superframe reserve capacity bits 620 2 750 Word duration seconds 2 0 0 6 Word capacity bits 100 30 Number of words within a frame 15 50 Technique for specifying satellite ephemeris Time reference 4 Position reference geodetic datum Geocentric Cartesian coordinates and their derivatives UTC SU PZ 90 Keplarian orbital elements and perturbation factors UTC USNO WGS84 a At the time of publication April 2007 there are 29 operational GPS satellites and 12 operational GLONASS satellites in orbit b Full GLONASS system operation will consist of 24 satellites and only 12 channels Such a system of simultaneous multiple transmissions is known as frequency division multiple access FDMA and distinguishes GLONASS from GPS which is a code division multiple access CDMA
32. Chairs finished wood vinyl fiberglass Packing and handling common polyethylene bags wraps envelopes and bubble pack pack foam common plastic trays and tote boxes Assembly cleaning and repair areas spray cleaners common solder sucker common soldering irons common solvent brushes synthetic bristles cleaning drying and temperature chambers GPS Reference Manual Rev 0l 57 Chapter 13 Electrostatic Discharge Control ESD Practices 13 4 Handling Printed Circuit Boards 58 ESD damage to unprotected sensitive devices may occur at any time ESD events can occur far below the threshold of human sensitivity Follow this sequence when it becomes necessary to install or remove a circuit board 1 After you are connected to the grounded wrist strap remove the circuit board from the frame and place it on a static controlled surface grounded floor or table mat Remove the replacement circuit board from the static shielding bag or clamshell and insert it into the equipment Place the original board into the shielding bag or clamshell and seal it with a label Do not put repair tags inside the shielding bag or clamshell Disconnect the wrist strap GPS Reference Manual Rev 0l 1PPS 2 D or 2D 3 D or 3D cc CCITT CD CD cd CDGPS CDMA CDPD CDU One Pulse Per Second Two Dimensional Three Dimensional Alternating Current Analog to Digital Analog to Digital Convertor Acc
33. EY NGS Information Services NOAA N NGS12 National Geodetic Survey SSMC 3 9202 1315 East West Highway Silver Spring MD 20910 3282 Phone 301 713 3242 Fax 301 713 4172 E Mail ngs infocenter noaa gov Website http www ngs noaa gov NAVSTAR GPS NAVSTAR GPS United States Naval Observatory USNO 3450 Massachusetts Avenue NW Washington DC 20392 5420 Phone 202 762 1467 Website http tycho usno navy mil gps html GLONASS Coordinational Scientific Information Center Moscow Russia Phone 7 495 333 72 00 Fax 7 495 333 81 33 E Mail glonass ianc 9 mcc rsa ru Website http www glonass ianc rsa ru GPS Reference Manual Rev 0l 51 Chapter 11 Standards References CDGPS Province of British Columbia Ministry of Sustainable Resource Management Base Mapping and Geomatic Services PO Box 9355 STN PROV GOVT Victoria BC Canada V8W 9M2 Phone 1 250 387 6316 Fax 1 250 356 7831 Website http www cdgps com OMNISTAR OmniSTAR Inc 8200 Westglen Drive Houston TX 77063 USA Phone 1 800 338 9178 U S amp Canada or 1 713 785 5850 E Mail dgps2 omnistar com Website http www omnistar com SOCIETY OF AUTOMOTIVE ENGINEERING SAE World Headquarters 400 Commonwealth Drive Warrendale PA 15096 0001 USA Phone 724 776 4841 Fax 724 776 0790 E Mail CustomerService sae org Website http www sae org servlets index 52 GPS Reference Manual Rev 0l Sections 12 1 to 12 4 list commonly used e
34. However because of errors in the IMU sensor measurements that accumulate over time an inertial only solution will degrade with time unless external updates such as position velocity or attitude are supplied NovAtel s SPAN system s combined GPS INS solution integrates the raw inertial measurements with all available GPS solution and raw measurement information to provide the optimum solution possible in any situation By using the high accuracy of the GPS solution the INS measurement errors can be modeled and mitigated Conversely the continuity and relative accuracy of the INS solution enables faster GPS signal re acquisition and RTK solution convergence The advantages of using SPAN technology are its ability to e Provide a full attitude solution roll pitch and azimuth e Provide continuous solution output in situations when a GPS only solution is impossible e Provide faster signal re acquisition and RTK solution resolution over stand alone GPS because of the tightly integrated GPS and IMU observations e Output high rate up to 100 Hz position velocity and attitude solutions for high dynamic applications e Use raw phase observation data to constrain INS solution drift even when too few satellites are available for a full GPS solution lt Refer to the SPAN Technology User Manual available from our website at http www novatel com support docupdates htm GPS Reference Manual Rev 0l 19 Chapter 3 Satellite Based Au
35. Manual Rev 0l L band Positioning Chapter 4 4 2 L band Service Levels Two levels of service are available Standard Sub meter accuracy from OmniSTAR VBS subscription required and CDGPS Extra Performance Decimeter accuracy from OmniSTAR XP subscription required High Performance Sub decimeter accuracy from OmniSTAR HP subscription required 4 2 1 Standard Service The OmniSTAR VBS service uses multiple GPS base stations in a solution and reduces errors due to the GPS signals travelling through the atmosphere It uses a wide area DGPS solution WADGPS and data from a relatively small number of base stations to provide consistent accuracy over large areas A unique method of solving for atmospheric delays and weighting of distant base stations achieves sub meter capability over the entire coverage area regardless of your location relative to any base station CDGPS is able to simultaneously track two satellites and incorporate the corrections into the position The output is SBAS like see WAAS32 WAASAS in the OEMV Family Firmware Reference Manual and can incorporate these corrections to generate differential quality position solutions CDGPS allows anyone within the area of coverage to take advantage of its benefits CDGPS and OmniSTAR VBS services are available on OEMV 1 and OEMV 3 based products NovAtel s ProPak V3 provides GPS with L band corrections in one unit using a common antenna This means that with CDGPS o
36. TAPPROXTIME command or RTCAEPHEM message The GPS Reference Manual Rev 0l 47 Chapter 10 TTFF and Satellite Acquisition RTCAEPHEM message contains GPS week and seconds and the receiver will use that GPS Time if the time is not yet known Several logs provide base station coordinates and the receiver will use them as an approximate position allowing it to compute satellite visibility Alternately you can set an approximate position by using the SETAPPROXPOS command or any of the following messages RTCAREF CMRREF or the RTCMV3 messages The OEMV does not use a real time clock Approximate time and position must be used in conjunction with a current almanac to aid satellite acquisition For a summary of the OEMV family command and logs used to inject an approximated time or position into the receiver see Table 4 or the OEMV Family Firmware Reference Manual Table 4 Approximate Time and Position Methods Approximate Command Log Time SETAPPROXTIME RTCAEPHEM Position SETAPPROXPOS RTCAREF or CMRREF or RTCM3 Base station aiding can help in environments such as urban canyons or forests where there can be frequent loss of lock or when no recent ephemerides new or stored are available A set of ephemerides can be injected into a rover station by broadcasting the RTCAEPHEM message from a base station GPS ephemeris is three frames long within a sequence of five frames Each frame requires 6 seconds of continuous lock t
37. a free component allows the receiver to track the carrier at lower signal to noise ratios Neuman Hoffman encoding reduces the effect of narrowband interference and improves the cross correlation properties between SV signals FEC encoding permits a receiver to correct errors introduced in the transmission process due to noise or interference and makes it easier to extract the navigation message from weak signals e 6dB stronger signal and more robust signal structure than L1 Greater reliability for safety of life applications interference mitigation worldwide and position accuracies are provided The OEMV 3 is hardware capable for tracking L5 but requires a future firmware upgrade to enable L5 positioning This will be available when a usable number of satellites are in orbit See also Section 7 2 NovAtel s GNSS Modernization on Page 39 1 For further information on the L5 signal you may wish to refer to NAVSAT GPS L5 Signal Specification Document No RTCA DO 261 See also RTCA contact details on Page 50 40 GPS Reference Manual Rev 0l Multipath signal reception is one of the most plaguing problems that detracts from the accuracy potential of GNSS differential positioning systems This section provides a brief look at the problems of multipath reception and some solutions Multipath antenna hardware solutions such as site selections away from structures that block the satellite signal or reflective surfaces that distort th
38. ading provides an estimate of the carrier phase observation on one frequency with the effects of the ionosphere removed It provides a different ambiguity value non integer than a simple measurement on that frequency The user s GPS antenna is moving In GPS this term is typically used with precise carrier phase positioning and the term dynamic is used with pseudorange positioning L band is a frequency range between 390 MHz and 1 55 GHz which is used for satellite communications and for terrestrial communications between satellite equipment L band includes the GPS carrier frequencies L1 L2 CDGPS and the OmniSTAR satellite broadcast signal See also Chapter 4 L band Positioning starting on Page 23 The 1575 42 MHz GPS carrier frequency which contains the course acquisition C A code as well as encrypted P code and navigation messages used by commercial GPS receivers See also Chapter 1 GPS Overview starting on Page The 1227 60 MHz secondary GPS carrier frequency containing only encrypted P code used primarily to calculate signal delays caused by the ionosphere Currently GPS satellites transmit the civilian C A code on the L1 frequency and the military P Y code on both the L1 and L2 frequencies New Block IIR M GPS satellites will transmit the same signals as previous GPS satellites but will also have a new signal called L2C on the L2 frequency See also Chapter 1 GPS Overview starting on Page 9 and Chapter 7 L2C Overview
39. al Oscillator Original Equipment Manufacturer Operational Parameters Open Service Pulsed Aperture Correlator Personal Computer Phase Centre Precise Code Power Up Built In Test Printed Circuit Board Personal Computer Memory Card International Association Power and Data Card Power Distribution Function Portable Document File Position Dilution Of Precision Pseudorange Delta Phase Parameters of the Earth 1990 see PZ90 Position Indicator Phase Lock Loop Parts Per Million Point to Point Protocol Precise Positioning Service or Pulse Per Second PseudoRandom Noise Number Public Regulated Service Part Serial Number Pseudorange Position Valid Position Velocity Time Parametry Zemli 1990 see PE 90 Quadrature Data Free Channel Random Access Memory Remote Access Service Rescue Coordination Centre Radio Frequency GPS Reference Manual Rev 0l Acronyms RFDC Chapter 14 Radio Frequency Direct Current Radio Frequency Uplink Right Hand Circular Polarization Ring Indicator Receiver Independent Exchange Format Ring Laser Gyro Restriction of the use of Hazardous Substances Raw Measurements Read Only Memory Return Material Authorization Root Mean Square Residual Solution Status Real Time Clock Radio Technical Commission for Aviation Services Radio Technical Commission for Maritime Services RTCM Version 3 0 Real Time Kinematic Request To Send Received Data SMART ANTENNA Selective Availab
40. alileo Chapter 6 will be equipped with a transponder which is able to transfer the distress signals from the user transmitters to the Rescue Co ordination Centre RCC which will then initiate the rescue operation At the same time the system will provide a signal to the user informing them that their situation has been detected and that help is under way This latter feature is new and is considered a major upgrade compared to the existing system which does not provide a feedback to the user Five categories of services have been defined 1 A free Open Service OS 2 Ahighly reliable Commercial Service CS 3 A Safety of Life Service SOL 4 A government encrypted Public Regulated Service PRS 5 A Search and Rescue Service SAR 6 1 1 Open Service This single frequency service will involve the provision of a positioning navigation and precise timing service It will be available for use by any person in possession of a Galileo receiver No authorisation will be required to access this service Galileo is expected to be similar to GPS in this respect The principal applications will be general navigation and positioning network timing traffic information systems systems including information on alternative routes in the event of congestion and wireless location for example with mobile telephony Studies clearly show that the availability of these services will be significantly enhanced by the existence of a greater number of
41. ansistor Logic Media Access Control Ethernet Multipath Assessment Tool Megabit Megabyte Multiplexed Binary Offset Carrier Multipath Estimating Delay Lock Loop Medium Earth Orbit Multipath Elimination Technology Meteorological Military Grid Reference System MegaHertz Management Information Base Military Multiple Independent NOmadic Stargazer Mark Input Mission Key Management Facility Multimedia Communications Exchange Lucent Multipath Mitigation Technology Minimum Operational Performance Standard Message Processor Modulated Precision Clock Multipath Meter Millisecond MTSAT Satellite Based Augmentation System Japan Mobile Satellite Most significant bit Mean sea level Measure Output Mean Time Between Failures Multi Functional Transport Satellite Not Applicable GPS Reference Manual Rev 0l 63 Chapter 14 64 NAS NASA NTS NAV NAVSTAR N C or NC NCC PZ90 Q Channel RAM RAS RCC RF Acronyms National Airspace System U S National Aeronautics and Space Administration U S National Topographic Series Canada RINEX Ephemeris File NAVigation Satellite Timing And Ranging synonymous with GPS Not Connected Network Control Center OmniSTAR Numerically Controlled Oscillator Navigation Data Neuman Hoffman National Marine Electronics Association Nautical mile Network Operations Center Nanosecond Non Volatile Memory RINEX Observation File Oven Controlled Cryst
42. apter 1 GPS Overview 1 1 GPS System Design The GPS system design consists of three parts e The Space segment e The Control segment e The User segment All these parts operate together to provide accurate three dimensional positioning timing and velocity data to users worldwide 1 1 1 The Space Segment The space segment is composed of the NAVSTAR GPS satellites The constellation of the system consists of 24 satellites in six 55 orbital planes with four satellites in each plane plus room for spares The orbit period of each satellite is approximately 12 hours at an altitude of 20 183 kilometers This provides a GPS receiver with at least six satellites in view from any point on Earth at any particular time The GPS satellite signal identifies the satellite and provides the positioning timing ranging data satellite status and the corrected ephemerides orbit parameters of the satellite to the users The satellites can be identified either by the Space Vehicle Number SVN or the Pseudorandom Code Number PRN The PRN is used by the NovAtel receiver The GPS satellites transmit on several L band frequencies L1 is centered at 1575 42 MHz L2 at 1227 60 MHz and L5 at 1176 45 MHz The L1 carrier is modulated by the C A code Coarse Acquisition and the P code Precision which is encrypted for military and other authorized users The L2 carrier is modulated with the P code and L2C civilian code beginning with the GPS IIR M sat
43. asurement or double difference carrier phase observation when the difference of the L1 and L2 measurements is used It is a carrier phase observable formed by subtracting L2 from L1 carrier phase data b b Dy The corresponding wavelength is 86 2 cm An ellipsoid designed to fit the shape of the entire Earth as well as possible with a single ellipsoid It is often used as a reference on a worldwide basis while other ellipsoids are used locally to provide a better fit to the Earth in a local region GPS uses the centre of the WGS84 ellipsoid as the centre of the GPS ECEF reference frame An encrypted form of P code Satellites transmit Y Code in replace of P code when Anti Spoofing is in effect See P Code and Anti Spoofing GPS Reference Manual Rev 0l A acceleration 19 31 49 accelerometers 19 accuracy 41 69 positioning 16 versus precision 12 acquisition almanac aid 67 and TTFF 47 coarse C A 10 42 68 INS solution 19 L1 73 L5 40 SPAN 19 with PAC 41 address 50 67 Aeronautical Radio Navigation Services ARNS 40 almanac 10 47 48 67 altitude 9 10 77 ambiguity 67 68 70 72 76 78 antenna 46 active 15 dual frequency 15 models 15 single frequency 15 site 17 antipodal satellites 32 67 anti static 56 58 ASCH 67 74 ascii 67 atmosphere 14 27 42 45 attenuation 67 attitude 19 autonomous 19 azimuth 19 67 B band pass filtering 15 baseline
44. at allows the range to the receiver to be calculated using the satellite s unique identity C A code is modulated by a chipping sequence To convert code chips to meters for the L1 frequency divide the speed of light by the signal s chipping rate which for L1 is 1 023 MHz so that 1 chip 293 05 m The pseudorange is measured to four satellites and solved for four unknowns x y z and t where 1t is the clock bias However other error sources exist which are not so easily removed For example satellite orbit and satellite clock errors come from the satellite Atmospheric errors such as ionospheric and tropospheric errors can be larger than those due to multipath Software models are used to compensate for these There may be errors from radio frequency RF noise such as jamming Closer to the antenna there are also receiver noise errors filtering errors and multipath errors We concentrate on the latter in here GPS Reference Manual Rev 0l Multipath Chapter 9 The pseudorange is calculated by measuring the time delay At see also Figure 16 between the received signal code from the satellite and the replica code generated by the receiver The pseudorange measurement is given by psuedorange Atx C where C is the speed of light Code from satellite Code replicated in receiver At i Figure 16 Time D
45. ber of available hardware channels Sequential receivers periodically reassign hardware channels to particular satellite signals in a predetermined sequence NovAtel s Waypoint Software Concurrent period of time between two observation files at two different stations One of the two stations will be the remote and the other will be the master The arrow on the screen will be pointing from the master to the remote The direction is determined by GrafNet in order to form loop closures as well as to minimize the number of legs from a control point Each session will be processed individually and combined in either a network adjustment or traverse solution A session can have different statuses and colors depending on whether certain tests passed or failed A sidereal day is the rotation period of the Earth relative to the equinox and is equal to one calendar day the mean solar day minus approximately four minutes Signal Quality Monitoring SQM technology is used to monitor GNSS and GEO signals in space for anomalous behavior The radius of a sphere centred at the user s true location that contains 50 percent of the individual three dimensional position measurements made using a particular navigation system Sometimes known as ellipsoid a perfect mathematical figure which very closely approximates the geoid Used as a surface of reference for geodetic surveys A positioning service made available by the United States Department of Defen
46. bility 47 48 SBAS 20 21 segment 10 30 67 68 self test 48 59 sidereal day 31 77 Signal Quality Monitoring SQM 77 signals 47 single point positioning 12 16 17 SNAS Chinese SBAS 20 space vehicle number SVN 10 42 SPAN technology 19 speed 75 Spherical Error Probable SEP 77 spheroid 11 77 78 static 12 15 28 56 58 statistics 26 68 71 76 77 steer 69 72 support 8 50 survey differential 14 dual frequency 39 geodetic 70 77 government 12 25 51 GPS Reference Manual Rev 0l RTK 43 US foot 53 SVN see space vehicle number synchronize 72 T TCXO see oscillators time 29 35 39 42 43 48 55 time to first fix TTFF 47 48 track 69 77 78 tracking satellite acquisition and TTFF 47 49 67 base station 10 carrier phase 68 CDGPS 27 correlators 41 43 45 cycle slip 69 Doppler aiding 70 ECEF coordinates 13 GLONASS 29 30 L2C 39 L5 40 Observation set 74 OmniSTAR 24 SafeTrak 76 troposphere 16 17 42 71 U U S National Geodetic Survey 51 uncertainty 12 70 undulation 11 78 update rate 41 78 upgrade 24 upgrade firmware 8 uplink 21 23 68 user segment 30 UTC see Coordinated Universal Time V variable field 78 velocity GLONASS 30 31 GNSS 9 10 70 72 number of satellites 10 precise service 75 SPAN 19 GPS Reference Manual Rev 0l Index SSII dynamics 49 vertical 29 71 78 W WAAS US SBAS 2
47. c error is much larger than the noise and multipath error e tropospheric effects These produce typical position errors of approximately 1 cm per 10 km of baseline length This error increases if there is a significant height difference between the base and rover stations as well as if there are significantly different weather conditions between the two sites A related issue is that of multipath interference the dominant error on short differential baselines Generally multipath can be reduced by choosing the antenna s location with care and by the use of a GPS 700 family antenna no need for a choke ring or a L1 L2 antenna and a choke ring antenna ground plane See also Table 1 on Page 15 and Chapter 9 Multipath starting on Page 41 GPS Reference Manual Rev 0l 17 Chapter 1 GPS Overview Convergence Time The position estimate becomes more accurate and more precise with time However convergence time is dependent upon baseline length while good results are available after a minute or so for short baselines the time required increases with baseline length Convergence time is also affected by the number of satellites which can be used in the solution the more satellites the faster the convergence and by the errors listed in Baseline Length above 18 GPS Reference Manual Rev 0l Chapter 2 SPAN Inertial Navigation Overview GPS positioning observes range measurements from orbiting Global Positioning System Satellites From thes
48. ce which is available to all GPS civilian users on a continuous worldwide basis typically using C A Code Sometimes used as SVID A unique number assigned to each satellite for identification purposes The space vehicle is a GPS satellite Time Dilution of Precision See Dilution of Precision DOP The number of hours per day when four or more satellites are available with acceptable positioning geometry Four visible satellites are required to determine location and altitude Navigation mode in which altitude and horizontal position are determined from satellite range measurements NovAtel s Waypoint Software Such a point may also be called a loop tie closure and is formed when two or more sessions point to it Thus there is a redundant determination at this point The actual time required by a GPS receiver to achieve a position solution This specification will vary with the operating state of the receiver the length of time since the last position fix the location of the last fix and the specific receiver design The single resultant direction from a point of departure to a point of arrival or subsequent position at any given time may be considered synonymous with Course Made Good GPS Reference Manual Rev 0l 77 Chapter 15 Traverse Station True Bearing True Heading Two Dimensional 2D Coverage Two Dimensional Navigation Undulation Update Rate UTC VDOP Variable Field Waypoint Wide
49. ces Severe multipath conditions could skew range measurements by as much as 100 meters or more See also Chapter 9 Multipath starting on Page 41 1 3 4 4 RTK When referring to the performance of RTK software two factors are introduced baseline length and convergence time Baseline Length Baseline length the position estimate becomes less precise as the baseline length increases Note that the baseline length is the distance between the phase centres of the two antennas Identifying the exact position of your antenna s phase centre is essential this information is typically supplied by the antenna s manufacturer or vendor The RTK software automatically makes the transition between short and longer baselines but the best results are obtained for baselines less than 10 km The following are factors which are related to baseline length ephemeris errors These produce typical position errors of 0 75 cm per 10 km of baseline length ionospheric effects The dominant error for single frequency GPS receivers on baselines exceeding 10 km Differential ionospheric effects reach their peak at around 2 pm local time being at a minimum during hours of darkness Ionospheric effects can be estimated and removed on dual frequency GPS receivers greatly increasing the permissible baseline length but at the cost of introducing additional noise to the solution Therefore this type of compensation is only used in cases where the ionospheri
50. d by the different correlation technologies As can be seen standard correlators are susceptible to substantial multipath biases for C A code chip delays of up to 1 5 code chips with the most significant C A code multipath bias errors occurring at about 0 25 to 0 75 code chips approaching 80 m error The Narrow Correlator tracking technology multipath susceptibility peaks at about 0 2 code chips about 10 m error and remains relatively constant out to 0 95 code chips where it rapidly declines to negligible error after 1 1 code chips On the other hand the PAC 1 NovAtel s GPS Receiver The High Performance OEM Sensor Of The Future Pat Fenton Bill Falkenberg Tom Ford and Keith Ng NovAtel Inc AJ Van Dierendonck AJ Systems http www novatel com Documents Papers File1 pdf 2 Theory and Performance of the Pulse Aperture Correlator J Jones P Fenton and B Smith NovAtel Inc http www novatel com Documents Papers PAC pdf GPS Reference Manual Rev 0l Multipath Chapter 9 technology multipath susceptibility peaks at about 0 1 code chips about 5 m error then reduces to a negligible amount at about the 0 2 code chip mark While positioning in single point mode the multipath and ranging improvement benefits of a PAC technology receiver versus narrow or standard correlators are overridden by a multitude of GNSS system biases atmospheric and other errors With or without PAC in single point mode positioning accuracy will be
51. d road tolls GPS Reference Manual Rev 0l 37 Chapter 6 Galileo Controlled access to this service for end users and the providers of value added services will be based on protected access keys in the receivers This will also enable revenue to be collected from users The commercial service will be transmitted in the E6 frequency band at 1278 75 MHz 6 1 3 Safety of Life Service The safety of life service will be offered to users who are highly dependant on precision signal quality and signal transmission reliability It will offer a high level of integrity and consequently provide the user with a very rapid warning of any possible malfunctions It will need to be certified in accordance with the regulations applicable to the various modes of transport the International Civil Aviation Organization ICAO regulations in the case of air transport the International Maritime Organization IMO regulations in the case of sea transport This service will require specialised receivers providing access to this enhanced quality signal The safety of life service will be transmitted in two frequency bands L1 at 1575 42 MHz and E5b at 1207 14 MHz Users may receive signals from the two frequency bands independently 6 1 4 Public Regulated Service The PRS will be a restricted access service offered to government agencies that require a high availability navigation signal The PRS service will utilize ranging codes that are encrypted with a
52. e 2001 2002 24 RIMS C receivers Integrity Channel SNAS China 2000 2002 e 73 WAAS WRS receivers WAAS USA 1996 1999 1st Generation e 148 WRS receivers e 21 GUS receivers WAAS G Il Receivers Technology Refresh 2004 2006 e 160 WAAS G II receivers Geostationary Command amp Control Segment 2004 2007 17 L1 L5 Signal Generators e 19 L1 L5 GUS receivers 6 NLES GUS receivers 4 UPC receivers Key A Wide Area Master Station Wide Area Reference or Earth Station EGNOS RIMS Site GAGAN India 2005 e 18 WAAS G Il receivers 3L1 L5 GUS receivers e 3 L1 L5 Signal Generators Figure 6 SBAS and NovAtel GRAS Australia 2007 e 23 WAAS G II receivers 1 Last updated in August 2007 GPS Reference Manual Rev 0l Satellite Based Augmentation System Chapter 3 3 1 SBAS is made up of a series of Reference Stations Master Stations Ground Uplink Stations and Geo stationary Satellites GEOs see Figure 7 The SBAS Concept on Page 22 The Reference Stations which are geographically distributed pick up GPS satellite data and route it to the Master Stations where wide area corrections are generated These corrections are sent to the Ground Uplink Stations which up link them to the GEOs for re transmission on the GPS L1 frequency These GEOs transmit signals which carry accuracy and integrity messages and which also provide additional ranging signa
53. e between a pair of stations for which simultaneous GPS data has been collected 2 NovAtel s Waypoint Software Connection between two stations with one or more sessions Normally a session and a baseline can be considered the same However in some cases there may be more than one session per baseline This is called a duplicate session baseline and it is plotted yellow on the screen The GPS receiver which is acting as the stationary reference It has a known position and transmits messages for the rover receiver to use to calculate its position GPS Reference Manual Rev 0l 67 Chapter 15 Bearing Broadcast Ephemerides Canada Wide Differential Global Positioning System CDGPS Carrier Carrier Phase Ambiguity Carrier Phase Measurements C Band Check Point Checksum Circular Error Probable CEP Coarse Acquisition C A Code Communication Protocol Control Point Control Segment 68 Glossary The horizontal direction of one terrestrial point from another terrestrial point expressed as the angular distance from a reference direction usually measured from 000 at the reference direction clockwise through 360 The reference point may be True North Magnetic North or Relative ship s head A set of parameters which describe the location of satellites with respect to time and which are transmitted broadcast from the satellites The CDGPS system is a free Canada wide DGPS service that is acc
54. e observations the receiver can compute position and velocity with high accuracy NovAtel GPS positioning systems have been established as highly accurate positioning tools however GPS in general has some significant restrictions which limit its usefulness in some situations Accurate GPS positioning requires line of site view to at least four satellites simultaneously If these criteria are met differential GPS positioning can be accurate to within a few centimetres If however some or all of the satellite signals are blocked the accuracy of the position reported by GPS degrades substantially or may not be available at all In general an Inertial Navigation System INS uses forces and rotations measured by an IMU to calculate acceleration velocity and attitude This capability is embedded in the firmware of our plus and OEMV series of receivers Forces are measured by accelerometers in three perpendicular axes within the IMU and the gyros measure rotations around those axes Over short periods of time inertial navigation gives very accurate acceleration velocity and attitude output Since the IMU sensor measures changes in orientation and acceleration the INS determines changes in position and attitude The IMU must have prior knowledge of its initial position initial velocity initial attitude Earth rotation rate and gravity field Once these parameters are known an INS is capable of providing an autonomous solution with no external inputs
55. e signal are capable of achieving varying degrees of multipath reception reduction For example site selection A as seen in Figure 14 will mean less multipath reception than site selection B Figure 14 GNSS Signal Multipath vs Increased Antenna Height You must also have the correct antenna type for the types of frequencies for example L1 L2 or L band you are tracking These options however require specific conscious efforts on the part of the GNSS user In many situations especially kinematic few if any of the above solutions will be effective or even possible to incorporate By far the best solutions are those that require little or no special efforts in the field on the part of the GNSS user This is what makes NovAtel s internal receiver solutions so desirable and practical NovAtel has placed long term concerted effort into the development of internal receiver solutions and techniques that achieve multipath reduction all of which are transparent to the receiver user These achievements have led first to Narrow Correlator tracking technology and then PAC technology that utilizes innovative patented correlator delay lock loop DLL techniques With patented PAC technology and a powerful 32 bit processor the OEMV family receivers offer multipath resistant processing at high data update rates Excellent acquisition and re acquisition times allow the receivers to operate in environments where very high dynamics and frequent inte
56. eal day such that after eight sidereal days the GLONASS satellites have completed exactly 17 orbital revolutions A sidereal day is the rotation period of the Earth relative to the equinox and is equal to one calendar day the mean solar day minus approximately four minutes Because each orbital plane contains eight equally spaced satellites one of the satellites will be at the same spot in the sky at the same sidereal time each day The satellites are placed into nominally circular orbits with target inclinations of 64 8 degrees and an orbital height of about 19 140 km which is about 1 050 km lower than GPS satellites The GLONASS satellite signal identifies the satellite and provides the positioning velocity and acceleration vectors at a reference epoch for computing satellite locations synchronization bits data age satellite health offset of GLONASS time from UTC SU formerly Soviet Union and now Russia almanacs of all other GLONASS satellites Some of the GLONASS transmissions initially caused interference to radio astronomers and mobile communication service providers The Russians consequently agreed to reduce the number of frequencies used by the satellites and to gradually change the L1 frequencies in the future to 1598 0625 1605 375 MHz Eventually the system will only use 12 primary frequency channels plus two additional channels for testing purposes GPS Reference Manual Rev 0l 31 Chapter 5 GLONASS O
57. ean Time Combined GPS and GLONASS NMEA talker ID Ground Global Navigation Satellite System Ground Plane GPS NMEA talker ID General Purpose Analog Input Global Positioning System Ground based Regional Augmentation System Australia GPS Reference Manual Rev 0l 61 Chapter 14 62 GRC GRCN GSS GSTB GTR GTS GUI GUS GUST GUSTR HDOP hex HFOM HMAC HP HTDOP Hz Iand Q I Channel IBIT IC ICAO ICD ICP ID IEC IEEE IERS IF IGP IGRF IGS CB IM IMLA IMO IMU INH INS YO IODE IOV IP IRQ ISG ISO ITRF JPL JTAG KPA Kb Acronyms Galileo Reception Chain Galileo Reception Chain Non PRS Galileo Sensor Stations Galileo System Test Bed Galileo Test Receiver Galileo Test Signal Generator Graphical User Interface Ground Uplink Station WAAS GUS Type 1 WAAS GUST Type 1 Receiver Horizontal Dilution Of Precision Hexadecimal Horizontal Figure of Merit Hashed Message Authentication Code High Performance standard OmniSTAR service Horizontal Position and Time Dilution Of Precision Hertz In Phase and Quadrature Channels In phase Data Channel Initiated Built In Test Integrated Circuit International Civil Aviation Organization Interface Control Document Integrated Carrier Phase Identification International Electrotechnical Commission Institute of Electrical amp Electronics Engineers International Earth Rotation Service Intermediate Frequency Ionospheric Grid Point
58. ect to time Strictly a specific point in time Typically when an observation is made A character or string of characters immediately preceded by a field delimiter NovAtel SUPERSTAR II based L1 receivers provide an estimated accuracy level The accuracy level estimate is provided in the horizontal and vertical Figure of Merit FOM The FOM reflects a 9596 confidence level for the position solution accuracy estimate The FOM accounts for all major sources of errors in the pseudoranges of the satellites used in the position solution The error sources which are included are ionospheric and tropospheric errors satellite position errors based on transmitted user range error and thermal noise Carrier phase ambiguity estimates which are set to a given number and held constant Usually they are set to integers or values derived from linear combinations of integers Carrier phase ambiguities which are set to values that are members of a predetermined set of discrete possibilities and then held constant A field in which the number of characters is fixed including the cyclic redundancy check CRC field Carrier phase ambiguities which are set to integer values and then held constant Programmable read only memory Galileo will be the Europe Union s own global navigation satellite system providing a highly accurate guaranteed global positioning service under civilian control The fully deployed Galileo system will consist of 30 satellites
59. eference System Service IERS Leap seconds are used to keep UTC close to mean solar time Mean solar time based on the spin of the Earth on its axis is not uniform and its rate is gradually changing due to tidal friction and other factors such as motions of the Earth s fluid core GLONASS time is maintained within 1 ms and typically better than 1 microsecond us of UTC SU by the control segment with the remaining portion of the offset broadcast in the navigation message As well Moscow offsets GLONASS time from UTC SU by plus three hours The GLOCLOCK log refer to the OEMV Family Firmware Reference Manual contains the offset information between GPS and GLONASS time Datum A datum is a set of parameters translations rotations and scale used to establish the position of a reference ellipsoid with respect to points on the Earth s crust If not set the receiver s factory default value is the World Geodetic System 1984 WGS84 GLONASS information is referenced to the Parametri Zemli 1990 PZ 90 or in English translation Parameters of the Earth 1990 PE 90 geodetic datum and GLONASS coordinates are reconciled in the receiver through a position filter and output to WGS84 See also the DATUM command in the OEMV Family Firmware Reference Manual available in PDF format from our website at http www novatel com support docupdates htm GPS Reference Manual Rev 0l GLONASS Overview Chapter 5 Table 2 Comparison of GLON
60. elay PAC improves accurate reception of C A code and also reduces the effect of multipath on pseudorange measurements The code accuracy is important to carrier phase positioning used in high accuracy applications such as real time kinematic RTK survey because the receiver can accurately start carrier phase measurements based on C A code Poor code measurements where a potential cause is multipath can lead to poor RTK fixes 9 1 2 Tracking Loops and Correlators PAC utilizes innovative patented correlator delay lock loop DLL techniques As stated previously correlators find the relationship in the code between the errors in position and time between measurements All GNSS receivers use correlators to track signals but consumer grade receivers typically use wide correlators In practice the GNSS signal is distorted to some extent by multipath and other phenomena Wide correlators track the distorted signal with some error Narrow correlators more easily reject this distortion 1 2 1 0 maenna 0 8 pe 0 6 bm 0 4 Amplitude 0 2 fem 0 0 1 5 3 Code Chips Figure 17 C A Code Distortion GPS Reference Manual Rev 0l 43 Chapter 9 Multipath 44 The NovAtel receiver uses the entire signal bandwidth broadcast by the GNSS satellites Consumer grade receivers typically band limit this signal to 2 MHz Figure 17 lon Page 43 shows that the narrower the filter becomes the more sinusoidal the transit
61. ellites Please see also Section 9 1 starting on Page 42 which includes a sub section on code and carrier 1 1 2 The Control Segment The control segment consists of a master control station five base stations and three data up loading stations in locations all around the globe The base stations track and monitor the satellites via their broadcast signals The broadcast signals contain the ephemeris data of the satellites the ranging signals the clock data and the almanac data These signals are passed to the master control station where the ephemerides are re computed The resulting ephemerides corrections and timing corrections are transmitted back to the satellites via the data up loading stations 1 1 3 The User Segment 10 The user segment such as the NovAtel receiver consists of equipment which tracks and receives the satellite signals The user equipment must be capable of simultaneously processing the signals from a minimum of four satellites to obtain accurate position velocity and timing measurements The NovAtel OEMV receiver can track 14 satellites which can occur at high latitudes GPS Reference Manual Rev 0l GPS Overview Chapter 1 1 2 Height Relationships What is a geoid An equipotential surface is any surface where gravity is constant This surface best represents mean sea level and not only covers the water but is projected throughout the continents In North America this surface is most commonly used at its
62. ems Service Version 2 3 Radio Technical Commission For Maritime Services 1800 North Kent St Suite 1600 Arlington VA 22209 USA Phone 1 703 527 2000 Fax 1 703 351 9932 E Mail information rtcm org Website http www rtcm org RTCA STANDARDS REFERENCE For copies of the Minimum Aviation System Performance Standards DGNSS Instrument Approach System Special Category 1 SCAT 1 contact RTCA Inc 1828 L Street NW Suite 805 Washington DC 20036 Phone 202 833 9339 Fax 202 833 9434 E Mail info rtca org Website http www rtca org GPS SPS SIGNAL SPECIFICATION REFERENCE For copies of the Interface Control Document ICD GPS 200 contact ARINC Research Corporation 2551 Riva Road Annapolis MD 21401 7465 Phone 800 633 6882 Fax 410 573 3300 Website http www arinc com 50 GPS Reference Manual Rev 0l Standards References Chapter 11 NMEA REFERENCE National Marine Electronics Association 0183 Standard for Interfacing Marine Electronic Devices NMEA Executive Director Seven Riggs Avenue Severna Park MD 21146 Phone 410 975 9425 Fax 410 975 9450 E Mail info nmea org Website http www nmea org GEODETIC SURVEY OF CANADA Natural Resources Canada Geodetic Survey Division Geomatics Canada 615 Booth Street Room 440 Ottawa Ontario Canada K1A OE9 Phone 613 995 4410 Fax 613 995 3215 E Mail information geod nrcan gc ca_ Website http www geod nrcan gc ca U S NATIONAL GEODETIC SURV
63. eological Survey Coordinated Universal Time Coordinated Universal Time former Soviet Union now Russia Volts Alternating Current Volts Direct Current Variable Frequency Virtual Base Station standard OmniSTAR service Voltage Controlled Temperature Compensated Crystal Oscillator Vertical Dilution of Precision Vacuum Fluorescent Display Vertical Figure of Merit Voltage Standing Wave Ratio Wide Area Augmentation System WAAS Reference Receiver G II Wide Area DGPS Waste Electrical and Electronic Equipment World Geodetic System Windows Hardware Quality Lab Microsoft WAAS Message Processor Week number of almanac Waypoint Extra Performance standard OmniSTAR service Crosstrack Error Zero Velocity Update GPS Reference Manual Rev 0l Chapter 15 Glossary Acquisition Address Field ADR Almanac Almanac Data Ambiguity Anti Spoofing Antipodal Satellites ASCII Attenuation Azimuth Baseline Base Station The process of locking onto a satellite s C A code and P code A receiver acquires all available satellites when it is first powered up then acquires additional satellites as they become available and continues tracking them until they become unavailable For sentences in the NMEA standard the fixed length field following the beginning sentence delimiter HEX 24 For NMEA approved sentences composed of a two character talker identifier and a three character sentence formatt
64. er For proprietary sentences composed of the character P HEX 50 followed by a three character manufacturer identification code Accumulated Doppler Range Carrier phase in cycles A set of orbit parameters that allows calculation of approximate GPS satellite positions and velocities The almanac is used by a GPS receiver to determine satellite visibility and as an aid during acquisition of GPS satellite signals A set of data which is downloaded from each satellite over the course of 12 5 minutes It contains orbital parameter approximations for all satellites GPS to universal standard time UTC conversion parameters and single frequency ionospheric model parameters The integer number of carrier cycles between a satellite and receiver Denial of the P code by the Control Segment is called Anti Spoofing It is normally replaced by encrypted Y code see P Code and Y Code Antipodal satellites are satellites in the same orbit plane separated by 180 degrees in argument of latitude A 7 bit wide serial code describing numbers upper and lower case characters special and non printing characters Typically used for textual data Reduction of signal strength The horizontal direction of a celestial point from a terrestrial point expressed as the angular distance from 000 reference clockwise through 360 The reference point is generally True North but may be Magnetic North or Relative ship s head 1 The lin
65. essible coast to coast throughout most of the continental United States and into the Arctic See also Section 4 1 2 Canada America Wide CDGPS starting on Page 25 for more information The steady transmitted RF signal whose amplitude frequency or phase may be modulated to carry information The number of integer carrier phase cycles between the user and the satellite at the start of tracking Sometimes ambiguity for short These are Accumulated Doppler Range ADR measurements They contain the instantaneous phase of the signal modulo 1 cycle plus some arbitrary number of integer cycles Once the receiver is tracking the satellite the integer number of cycles correctly accumulates the change in range seen by the receiver When a lock break occurs this accumulated value can jump an arbitrary integer number of cycles this is called a cycle slip C Band is the original frequency allocation for communications satellites C Band uses 3 7 4 2 GHz for downlink and 5 925 6 425 Ghz for uplink NovAtel s Waypoint Software A station with known coordinates but these coordinates are only used as a check against GrafNet s computed coordinates By NMEA standard a validity check performed on the data contained in the sentences calculated by the talker appended to the message then recalculated by the listener for comparison to determine if the message was received correctly Required for some sentences optional for all others Ci
66. etres at the horizon Ephemeris Errors Some degree of error always exists between the broadcast ephemeris predicted satellite position and the actual orbit position of the satellites These errors directly affect the accuracy of the range measurement Satellite Clock Errors Some degree of error also exists between the actual satellite clock time and the clock time predicted by the broadcast data This broadcast time error causes some bias to the pseudorange measurements Receiver Clock Errors Receiver clock error is the time difference between GPS receiver time and true GPS Time All GNSS receivers have differing clock offsets from GPS Time that vary from receiver to receiver by an unknown amount depending on the oscillator type and quality TCXO versus OCXO and GPS Reference Manual Rev 0l GPS Overview Chapter 1 so on However because a receiver makes all of its single point pseudorange measurements using the same common clock oscillator all measurements are equally offset and this offset can generally be modeled or quite accurately estimated to effectively cancel the receiver clock offset bias Thus in single point positioning receiver clock offset is not a significant problem Multipath Multipath signal reception can potentially cause large pseudorange and carrier phase measurement biases Multipath conditions are very much a function of specific antenna site location versus local geography and man made structural influen
67. euman Hoffman code 40 NMEA 51 67 68 74 78 nmea 34 noise number 64 non volatile memory NVM 47 74 NovAtel Inc 2 50 null field 74 81 Index 82 O observation set 73 74 OCXO see oscillators offset 34 OmniSTAR 23 24 27 28 75 operational satellites 9 29 35 orbital 10 30 31 35 67 68 71 72 oscillators 16 17 64 66 overview 36 39 40 P PAC technology 41 44 45 parallel receiver 75 parity 75 path 42 56 69 P code 10 32 67 73 75 78 perigee 75 phase center 15 pitch 19 position 47 power 47 48 precision 10 12 14 PRN number 10 20 28 32 42 74 75 processing Doppler aiding 70 post mission 15 real time 12 15 user equipment 10 propagation 16 46 pseudolite 75 pseudorange 14 16 17 43 75 pulse 59 64 PZ 90 34 35 Q quadrature Q data free channel 40 73 R radio frequency RF 68 range 16 17 19 42 68 71 73 75 71 78 re acquisition 47 49 76 real time 14 15 23 29 43 76 receiver 33 reflectors 42 relative positioning see differential positioning reset 34 residual 76 revision manual 2 84 RMS see root mean square roll 19 root mean square RMS 76 rotation 19 31 34 69 route 21 69 76 rover station 14 RT 2 76 RT 20 76 RTCA 50 RTCM 50 RTK 17 19 27 28 43 76 S SafeTrak 76 satellite 49 acquisition 47 almanac 67 clock 16 orbit arrangement 9 visi
68. ev 0l 27 Chapter 4 L band Positioning 4 3 L band Commands and Logs The ASSIGNLBAND command allows you to set OmniSTAR or CDGPS base station communication parameters It should include relevant frequency and data rate for example assignlband omnistar 1536782 1200 Or assignlband cdgps 1547547 4800 The PSRDIFFSOURCE command lets you identify from which source to accept RTCA1 RTCMI CDGPS or OmniSTAR VBS differential corrections For example in the PSRDIFFSOURCE command OMNISTAR enables OmniS TAR VBS and disables other DGPS types AUTO means the first received RTCM or RTCA message has preference over an OmniSTAR VBS or CDGPS message The RTKSOURCE command lets you identify from which source to accept RTK RTCM RTCMV3 RTCA CMR CMRPLUS and OmniSTAR HP or XP differential corrections For example in the RTKSOURCE command OMNISTAR enables OmniSTAR HP or XP if allowed and disables other RTK types AUTO means the NovAtel RTK filter is enabled and the first received RTCM RTCA or CMR message is selected and the OmniSTAR HP or XP message if allowed is enabled The position with the best standard deviation is used in the BESTPOS log The HPSEED command allows you to specify the initial position for OmniSTAR HP The HPSTATICINIT command allows you to speed up the convergence time of the HP or XP process when you are not moving The PSRDIFFSOURCE and RTKSOURCE commands are useful when the receiver is receiving corrections from multip
69. ferential Positioning In single point positioning coordinates of a GPS receiver at an unknown location are sought with respect to the Earth s reference frame by using the known positions of GPS satellites being tracked The position solution generated by the receiver is initially developed in Earth Centered Earth Fixed ECEF coordinates which can subsequently be converted to any other coordinate system See Figure 4 on Page 13 for a definition of the ECEF coordinates With as few as four GPS satellites in view the absolute position of the receiver in three dimensional space can be determined Only one receiver is needed Definitions Origin Earth s center of mass Z Axis Parallel to the direction of the Conventional Terrestrial Pole CTP for polar motion as defined by the Bureau International de l Heure BIH on the basis of the coordinates adopted for the BIH stations X Axis Intersection of the WGS 84 Reference Meridian Plane and the plane of the CTP s Equator the Reference Meridian being parallel to the Zero Meridian defined by the BIH on the basis of the coordinates adopted for the BIH stations Y Axis Completes a right handed earth centered earth fixed ECEF orthogonal coordinate system measured in the plane of the CTP Equator 909 East of the X Axis BIH Defined CTP 1984 0 WGS 84 ac Earth s Center of Mass BIH Defined Zero Meridian 1984 0 S P Y WGS 84 X WGS 84 Analogous to the
70. gmentation System 20 A Satellite Based Augmentation System SBAS is a type of geo stationary satellite system that improves the accuracy integrity and availability of the basic GPS signals Accuracy is enhanced through the use of wide area corrections for GPS satellite orbits and ionospheric errors Integrity is enhanced by the SBAS network quickly detecting satellite signal errors and sending alerts to receivers to not use the failed satellite Availability is improved by providing an additional ranging signal to each SBAS geo stationary satellite SBAS includes the Wide Area Augmentation System WAAS the European Geo Stationary Navigation System EGNOS and the MTSAT Satellite Based Augmentation System MSAS The Chinese SNAS Indian GAGAN and Australian GRAS systems are in progress At the time of publication there are two WAAS satellites over the Pacific Ocean PRN 135 and PRN 138 an EGNOS satellite over the eastern Atlantic Ocean PRN 120 an EGNOS satellite over the Indian Ocean PRN 126 and another EGNOS GEO satellite over the African mid continent PRN 124 SBAS data is available from any of these satellites and more satellites will be available in the future lt Since July 2003 WAAS has been certified for Class 1 Class 2 civilian aircraft navigation Figure 6 shows the regions applicable to each SBAS system mentioned in the paragraph above and how NovAtel is involved in each of them EGNOS Europ
71. ility Society of Automotive Engineers Search and Rescue Search and Rescue Satellite Aided Tracking Satellite Based Augmentation System Safety Computer Special Category I Standard Deviation Spherical Error Probable Signal Generator Soviet Geodetic System 1990 Syst me Internationale WAAS GUS Type 1 Signal Generator Signal in Space Serial Line Internet Protocol Satellite Navigation Augmentation System China Signal to Noise Ratio Safety of Life Standard Position Service Symbols Per Second Synchronized Position Attitude Navigation Signal Quality Monitoring Static Random Access Memory SUPERSTAR II former Soviet Union now Russia Space Vehicle Space Vehicle Identifier Space Vehicle Number Software Software Replacement Unit Transmission Control Protocol GPS Reference Manual Rev 0l 65 Chapter 14 66 TCXO TDOP TES TIL TNM TOA TOE TOW TRAIM TTFF TTL ZUPT Acronyms Temperature Compensated Crystal Oscillator Time Dilution Of Precision Time Estimator Status Time Integrity Limit Telecommunications Network Management Time of Almanac Time of Ephemeris Time of Week Time Receiver Autonomous Integrity Monitor Time To First Fix Transistor Transistor Logic Time to Narrow Lane Transient Voltage Suppressor Transmitted Data Universal Asynchronous Receiver Transmitter User Datagram Protocol User Differential Range Error Ultra High Frequency Universal Serial Bus United States G
72. ilution of Precision factors e decreased occupation times means faster RTK results In order to determine a position in GPS only mode the receiver must track a minimum of four satellites representing the four unknowns of 3 D position and time In combined GPS GLONASS mode the receiver must track five satellites representing the same four previous unknowns and at least one GLONASS satellite to determine the GPS GLONASS time offset With the availability of combined GPS GLONASS receivers users have access to a potential 48 satellite combined system With 48 satellites performance in urban canyons and other locations with restricted visibility such as forested areas improves as more satellites are visible in the non blocked portions of the sky A larger satellite constellation also improves real time carrier phase differential positioning performance Russia has committed itself to bringing the system up to the required minimum of 18 active satellites by the end of 2007 and signed an agreement with India that provides for the launches of GLONASS satellites on Indian launch vehicles At the time of publication April 2007 there are 12 operational GLONASS satellites and one newly launched GLONASS satellite at its commissioning phase The Russian Government have set 2009 as the full deployment date of the 24 satellite constellation and ensured financial support to meet that date The OEMV 2 and OEMV 3 receivers acquire and track GPS and GLONASS
73. in the 960 1215 MHz frequency band already used worldwide for Aeronautical Radio Navigation Services ARNS as well as by the Department of Defense DoD Certain measures have been taken within the United States to ensure that L5 can coexist with government systems operating at the same or nearby frequencies The carriers of the L5 signal are modulated by two bit streams in phase quadrature The L5 power spectrum is contained within a 24 MHz band centered about L5 L5 power is increased by 6 dB compared to the L1 signal 154 dBW versus 160 dBW This is equally split between an in phase 1 data channel and a quadrature Q data free channel which improves resistance to interference especially from pulse emitting systems in the same band as L5 Both I and Q channels are encoded with the Neuman Hoffman codes The L5 signal is also Forward Error Correction FEC encoded Code Division Multiple Access CDMA techniques allow differentiation between the SVs since all SVs transmit the same L5 frequency The benefits of the L5 signal include e Signal redundancy where the L5 signal is completely redundant to the L1 signal creates frequency diversity and includes a direct acquisition capability so that you do not have to rely on the L1 and L2 signals for initial acquisition Civilian capability to perform ionospheric delay corrections Higher integrity level and continuity of service Enhanced interference rejection capabilities e Coherent dat
74. ion for Aeronautics RTCA Radio Technical Commission for Maritime Services RTCM Real Time Kinematic RTK SafeTrak Satellite Based Augmentation System SBAS Selective Availability SA Selected Waypoint 76 Glossary In a double difference implementation measurements are differenced between different satellites on one receiver in order to cancel the correlated errors Usually one satellite is chosen as the reference and all others are differenced with it See Base Station Bearing relative to heading or to the vessel See Rover Station In the context of measurement the residual is the misclosure between the calculated measurements using the position solution and actual measurements A probability level of 68 A planned course of travel usually composed of more than one navigation leg The GPS receiver which does not know its position and needs to receive measurements from a base station to calculate differential GPS positions The terms remote and rover are interchangeable NovAtel s Double Differencing Technology for real time kinematic RTK carrier phase floating ambiguity resolution An organization which developed and defined a message format for differential positioning An organization which developed and defined the SC 104 message format for differential positioning A type of differential positioning based on observations of carrier phase In NovAtel documents it is als
75. ions of the C A code become By utilizing PAC tracking techniques the receiver is capable of pseudorange measurement improvements better than 4 1 when compared to consumer grade wide correlation techniques and 2 1 when compared to narrow correlation techniques PAC dramatically reduces multipath reception This is due to PAC s narrowed and therefore more multipath resistant pattern than other correlators See also Figure 18 Comparison of Correlator Patterns below 0 3 0 3 o E 15 VA N f 41 5 15 A A 415 o N 7 Y o E e Zz 0 3 0 3 Delay C A chips Delay C A chips Narrow Correlator Patterns PAC Correlation Pattern Figure 18 Comparison of Correlator Patterns representations from paper not to scale 9 1 2 1 Pulse Aperture Correlator Technology PAC NovAtel s OEM4 and OEMV family of receivers achieve a higher level of pseudorange positioning performance versus standard wide or narrow correlator receivers by virtue of their celebrated PAC technology By utilizing PAC tracking techniques the receiver is capable of pseudorange measurement improvements better than 4 1 when compared to standard wide correlation techniques and 2 1 when compared to narrow correlation techniques The PAC technology dramatically reduces multipath reception by virtue of its very narrow correlation function Figure 19 Comparison of Multipath Envelopes on Page 45 illustrates relative multipath induced tracking errors encountere
76. l receiver clock error To derive the closest GPS Time you must subtract the clock offset shown in the TIME log from GPS Time reported refer to the OEMV Family Firmware Reference Manual 1 NovAtel User Manuals are available from our website at http www novatel com support docupdates htm GPS Reference Manual Rev 0l 33 Chapter 5 GLONASS Overview GPS Time is based on an atomic time scale Coordinated Universal Time as maintained by the U S Naval Observatory UTC USNO reported in NMEA logs is also based on an atomic time scale with an offset of an integer number of seconds with respect to GPS Time GPS Time is designated as being coincident with UTC USNO at the start date of January 6 1980 00 hours GPS Time does not count leap seconds and therefore an offset exists between UTC USNO and GPS Time at this date in April 2007 14 seconds The GPS week consists of 604800 seconds where 000000 seconds is at Saturday Sunday midnight GPS Time Each week at this time the week number increments by one and the seconds into the week resets to 0 5 222 GLONASS Time vs Local Receiver Time 5 3 34 GLONASS time is based on an atomic time scale similar to GPS This time scale is UTC as maintained by Russia UTC SU Unlike GPS the GLONASS time scale is not continuous and must be adjusted for periodic leap seconds Leap seconds are applied to all UTC time references as specified by the International Earth Rotation and R
77. le sources Several L band specific logs also exist and are prefixed by the letters RAWLBAND LBAND or OMNI CDGPS corrections are output similarly to SBAS corrections There are four SBAS fast corrections logs WAAS32 WAAS35 and one slow corrections log WAAS45 for CDGPS The CDGPS PRN is 209 D4 1 In addition to a NovAtel receiver with L band capability a subscription to the OmniSTAR or use of the free CDGPS service is required 2 All PSRDIFFSOURCE entries fall back to SBAS even NONE for backwards compatibility Refer to the OEMV Family Firmware Reference Manual for more details on individual L band commands and logs 28 GPS Reference Manual Rev 0l Chapter 5 GLONASS Overview The OEMV 1G based OEMV 2 based and OEMV 3 based products are GLONASS enabled with full code and carrier phase RTK positioning as well as the ability to record raw GPS and GLONASS measurements We discuss these capabilities further in this overview RTK performs significantly better when tracking both GPS and GLONASS satellites than when tracking GPS satellites only Adding GLONASS to GPS improves all aspects of satellite navigation and RTK operation availability reliability stability time of RTK initialization and so on The use of GLONASS in addition to GPS provides very significant advantages e increased satellite signal observations e markedly increased spatial distribution of visible satellites e reduced Horizontal and Vertical D
78. ls for added availability continuity and accuracy These GEO signals are available over a wide area and can be received and processed by NovAtel receivers with appropriate firmware GPS user receivers are thus able to receive SBAS data in band and use not only differential corrections but also integrity residual errors and ionospheric information for each monitored satellite The signal broadcast via the SBAS GEOs to the SBAS users is designed to minimize modifications to standard GPS receivers As such the GPS L1 frequency 1575 42 MHz is used together with GPS type modulation for example a Coarse Acquisition C A pseudorandom PRN code In addition the code phase timing is maintained close to GPS Time to provide a ranging capability The primary functions of SBAS include data collection determining ionospheric corrections determining satellite orbits determining satellite clock corrections determining satellite integrity independent data verification SBAS message broadcast and ranging system operations amp maintenance SBAS Receiver All OEMV models many OEM4 and several SSII models of NovAtel receivers are equipped with SBAS capability The ability to incorporate the SBAS corrections into the position is available in these models SBAS data can be output in log format and can incorporate these corrections to generate differential quality position solutions Standard SBAS data messages are analyzed based
79. lution of precision DOP 60 70 72 distance 53 Doppler 47 59 67 68 70 double difference 46 70 73 76 78 downlink 68 71 dynamic 19 27 41 49 73 E Earth coordinate system 70 core 34 crust 34 ellipsoid 78 environmental biases 16 parameters 34 perigee 75 reference frame 13 rotation 19 31 34 surface 32 70 71 UTC 69 earth centered earth fixed ECEF 13 70 78 eccentricity e 70 EGNOS European SBAS 20 electrostatic discharge ESD 56 58 elevation 24 41 47 48 70 74 ellipsoid 11 12 34 70 72 73 77 78 e mail 8 ephemeris 10 16 35 42 47 48 71 76 epoch 31 70 71 73 errors ephemeris 16 in single point positioning 14 multipath 74 pseudorange 69 ESD see electrostatic discharge F field command 67 71 74 78 electromagnetic 56 57 gravity 19 survey 41 figure of merit FOM 71 flash 71 forest 29 48 four unknowns 42 frequency 70 frequency division multiple access FDMA 35 G GAGAN Indian SBAS 20 Galileo 36 62 71 GDOP see dilution of precision GEO SBAS 21 geodesic 72 geodetic datum see datum Geodetic Survey of Canada 51 geoid 11 12 70 71 77 Geological Survey of Canada 25 geo stationary satellites 20 23 72 76 GPS Reference Manual Rev 0l GLONASS 15 30 31 33 35 GPS overview 9 10 12 14 42 standards and references 50 Time 16 33 34 47 48 GrafNav 29 gravity 11 19 71 great circle
80. ma followed by either the checksum delimiter HEX 2A or the sentence delimiters lt CR gt lt LF gt HEX ODOA Note the ASCII Null character HEX 00 is not to be used for null fields Term used to describe periods of time when a GNSS receiver s line of sight to GNSS satellites is blocked by natural or man made objects 1 Any measurement 2 NovAtel s Waypoint Software Raw measurement file collected from a receiver that is set up over a stationary point GrafNet only accepts GPB files Other formats must be converted first See the GrafNav Grafnet User Guide for supported formats GrafNet also requires single frequency carrier phase data as a minimum and accepts dual frequency if available Users wishing to perform code only processing should use GrafNav A set of receiver measurements taken at a given time which includes one time for all measurements and the following for each satellite tracked PRN number pseudorange or carrier phase or both lock time count signal strength and tracking status Only L1 measurements are included in the set The observation set is assumed to contain information indicating how many satellites it contains and which ones have L1 only and which ones have L1 L1 pairs GPS Reference Manual Rev 0l Glossary OmniSTAR Origin Waypoint Parallel Receiver Parity Perigee P Code PDOP Precise Positioning Service PPS PRN Number Pseudolite Pseudorange Pseudorange Measurements
81. mode It has been discussed that careful site selection and a GPS 700 series antenna or good antenna design combined with a choke ring ground plane are fairly effective means of reducing multipath reception Internal receiver solutions for multipath elimination are achieved through various types of correlation techniques where the standard correlator is the reference by which all other techniques can be compared PAC technology has a four fold advantage over standard correlators Reasons for this advantage are improved ranging measurements due to a sharper less noisy correlation peak and reduced susceptibility to multipath due to rejection of C A code delays of greater than 0 1code chip When used with a choke ring ground plane PAC technology provides substantial performance gains over standard or narrow correlator receivers operating in differential mode GPS Reference Manual Rev 0l IPIE MIU TTFF and Satellite Acquisition Time to First Fix TTFF is the time it takes the receiver to calculate a position after a reset or upon power up The TTFF varies and depends on what is stored in non volatile memory NVM at the time of power up and on what other information is available such as almanac ephemeris or time The speed at which the receiver locates and locks onto new satellites is improved if the receiver has approximate time and position as well as an almanac This allows the receiver to compute the elevation of each satellite so i
82. n the Earth s equatorial plane pointing to the Greenwich prime meridian the Z axis pointing to the north pole and the Y axis in the equatorial plane 90 from the X axis with an orientation which forms a right handed XYZ system A dimensionless measurement defined for a conic section where e 0 is a circle e lis anellipse 0 lt e lt 1 is a parabola and e gt 1 isa hyperbola The eccentricity of GPS is nominally 1 02 The angle from the horizon to the observed position of a satellite A smooth mathematical surface which represents the Earth s shape and very closely approximates the geoid It is used as a reference surface for geodetic surveys GPS Reference Manual Rev 0l Glossary Ellipsoidal Height Ephemeris Ephemeris Data Epoch Field Figure of Merit Fixed Ambiguity Estimates Fixed Discrete Ambiguity Estimates Fixed Field Fixed Integer Ambiguity Estimates Flash ROM Galileo Galileo Industries GaIn Geometric Dilution of Precision GDOP Geoid Chapter 15 Height above a defined ellipsoid approximating the surface of the Earth A set of satellite orbit parameters that are used by a GPS receiver to calculate precise GPS satellite positions and velocities The ephemeris is used in the determination of the navigation solution and is updated periodically by the satellite to maintain the accuracy of GPS receivers The data downlinked by a GPS satellite describing its own orbital position with resp
83. nk to 6 DGPS uplink L band geo stationary satellite L band DGPS signal Correction data are received and applied real time CON DO GPS Reference Manual Rev 0l 23 Chapter 4 L band Positioning 4 1 The OmniSTAR system is designed for coverage of most of the world s land areas A subscription charge by geographic area is required The CDGPS system is a free Canada wide DGPS service that is accessible coast to coast throughout most of the continental United States and into the Arctic By default the OEMV 1 OEMV 3 and ProPak V3 models with L band software support the standard CDGPS sub meter L1 L2 service and the OmniSTAR Virtual Base Station VBS sub meter L1 service The OmniSTAR VBS service is upgradeable on the OEMV 3 and ProPak V3 to the Extra Performance XP decimeter L1 L2 service or High Performance HP sub decimeter L1 L2 service via a coded message from an OmniSTAR satellite Coverage The two systems provide different coverage areas e OmniSTAR Most of the World s Land Areas e CDGPS Canada America Wide 4 1 1 OmniSTAR Geographic Areas 24 In most world areas a single satellite is used by OmniSTAR to provide coverage over an entire continent or at least very large geographic areas In North America a single satellite is used but it needs three separate beams to cover the continent The three beams are arranged to cover the East Central and Western portions of North America The same data is broadcast o
84. o collect the ephemeris data This gives a minimum of 18 s and a maximum of 36 s continuous lock time 10 2 SUPERSTAR Il based Products 48 The receiver enters Navigation mode refer to the Operational States section of the SUPERSTAR II User Manual and provides valid outputs in less than 45 s warm start after completion of the self test and the following initialization criteria have been met Valid time 10 minutes and position data 100 km from actual position Valid almanac data less than a year old At least 4 satellites greater than 5 elevation above the horizon HDOP lt 6 ic The maximum time for self test and device initialization is less than 5 seconds In the case where the following additional conditions are met the TTFF is reduced to 15 s hot start Unit has not been off for more than a week before nominal power is re applied e Last navigation fix occurred within the last 2 hours e Valid ephemeris data less than 4 hours old for at least 5 satellites With no initialization the time from power application to valid navigation output is typically 166 s GPS Reference Manual Rev 0l TTFF and Satellite Acquisition Chapter 10 cold start There is no disruption of navigation data output when a satellite signal is lost unless there is a power interruption for a period of less than or equal to 200 ms Also the receiver re acquires the satellite signal within 0 3 seconds after satellite visibility has been resto
85. o used with reference to RT 2 and RT 20 The receiver tracks a satellite by replicating the satellite s PRN code and aligning it with the received PRN code A cross correlation check is performed to check alignment and the cross correlation channel shifts its code phase repeatedly to measure the power If necessary the tracking channel re acquires the satellite to remove the cross correlation error A type of geo stationary satellite system that improves the accuracy integrity and availability of the basic GPS signals This includes WAAS EGNOS and MSAS See also Chapter 3 Satellite Based Augmentation System starting on Page 20 The method used in the past by the United States Department of Defence to control access to the full accuracy achievable by civilian GPS equipment generally by introducing timing and ephemeris errors The waypoint currently selected to be the point toward which the vessel is travelling Also called to waypoint destination or destination waypoint GPS Reference Manual Rev 0l Glossary Sequential Receiver Session Sidereal Day Signal Quality Monitoring SQM Spherical Error Probable SEP Spheroid Standard Positioning Service SPS Space Vehicle ID SV TDOP Three Dimensional Coverage hours Three Dimensional 3D Navigation Tie Point Time To First Fix TTFF Track Made Good Chapter 15 A GPS receiver in which the number of satellite signals to be tracked exceeds the num
86. oints and there must always be at least one 3 D point or else one horizontal and one vertical point per project Predetermined hardware or software activity designed to establish or maintain two machines or programs in synchronization Handshaking concerns the exchange of messages or packets of data between two systems with limited buffers Hardware handshaking uses voltage levels or pulses in wires to carry the handshaking signals Software handshaking uses data units for example binary bits carried by some underlying communication medium The direction in which a vessel points or heads at any instant expressed in degrees 000 clockwise through 360 and may be referenced to True North Magnetic North or Grid North The heading of a vessel is also called the ship s head Heading is a constantly changing value as the vessel oscillates or yaws across the course due to the effects of the air or sea cross currents and steering errors See Dilution of Precision DOP See Dilution of Precision DOP Carrier phase ambiguity estimates which are only allowed to take on integer values GPS Reference Manual Rev 0l Glossary Chapter 15 Iono Free Carrier Phase A linear combination of L1 and L2 carrier phase measurements which Observation Kinematic L band L1 Frequency L2 Frequency L5 Frequency Lane Local Observation Set Local Tangent Plane Low Latency Solution Magnetic Bearing Magnetic He
87. on RTCA standards for GPS WAAS airborne equipment Please refer to your SUPERSTAR II Firmware Reference Manual or OEMV Firmware Reference Manual for details on SBAS commands and logs An SBAS capable receiver permits anyone within the area of coverage to take advantage of its benefits with no subscription fee GPS Reference Manual Rev 0l 21 Chapter 3 Satellite Based Augmentation System 10 Figure 7 The SBAS Concept Reference Description Reference Description 1 Geo stationary Satellite GEO 8 C Band 2 GPS Satellite Constellation 9 SBAS Reference Station 3 L1 10 SBAS Master Station 4 L1 and C Band 11 Ground Uplink Station 5 L1 and L2 6 GPS User 7 Integrity data differential corrections and ranging control 22 GPS Reference Manual Rev 0l Chapter 4 L band Positioning The transmission of OmniSTAR or Canada Wide Differential Global Positioning System CDGPS corrections are from geo stationary satellites The L band frequency of these geo stationary satellites is sufficiently close to that of GPS that a common single antenna such as the NovAtel 702L may be used Both systems are portable and capable of sub meter accuracy over their coverage areas See Figure 8 g Q SE An e ty Figure 8 L band Concept Reference Description 1 GPS satellites 2 Multiple L band ground stations 3 Send GPS corrections to 4 4 Network Control Center where data corrections are checked and repackaged for upli
88. or any area They may be arranged prior to travelling to a new area or after arrival Contact OmniSTAR at www omnistar com for further details 1 Please see Page 52 for more OmniSTAR contact information GPS Reference Manual Rev 0l L band Positioning Chapter 4 4 1 2 Canada America Wide CDGPS In order to enable CDGPS positioning you must set the L band frequency for the geographically appropriate CDGPS signal using the ASSIGNLBAND command Refer to the OEMV Family Firmware Reference Manual or to Volume 2 of the OEM4 User Manual set The CDGPS signal is broadcast on 4 different spot beams on the MSAT 1 satellite Depending on your geographic location there will be a different frequency for the CDGPS signal as shown in Figure 9 Figure 9 CDGPS Frequency Beams The following are the spot beam names and their frequencies in KHz or Hz East 1547646 or 1547646000 East Central 1557897 or 1557897000 West Central 1557571 or 1557571000 West 1547547 or 1547547000 lt The CDGPS service does not include the MSAT Alaska Hawaii beam shown in Figure 9 The data signal is structured to perform well in difficult or foliated conditions so the service is available more consistently than other services and has a high degree of service reliability CDGPS features wide area technology possible spatial integrity with all Government of Canada maps and surveys 12 24 hour 7 days a week built in network redundancies and an openly
89. ovatel com support knowledgedb htm 8 GPS Reference Manual Rev 0l Chapter 1 GPS Overview The Global Positioning System GPS is a satellite navigation system capable of providing a highly accurate continuous global navigation service independent of other positioning aids GPS provides 24 hour all weather worldwide coverage with position velocity and timing information The system uses the NAVSTAR NAVigation Satellite Timing And Ranging satellites which consists of 24 active satellites to provide a GPS receiver with at least six satellites in view at all times A minimum of four satellites in view are needed to allow the receiver to compute its current latitude longitude altitude with reference to mean sea level and the GPS system time As of 2007 there are 30 operational satellites At the time of publications the current GPS constellation consists of 29 satellites and the most recent Block IIR M satellite was launched on September 26 2005 The GPS constellation and individual satellite status is updated every working day by NAVSTAR See Chapter 11 Standards References starting on Page 50 for their contact information and a link to their website Figure 1 NAVSTAR Satellite Orbit Arrangement lt NovAtel Application Notes on the topics covered in this reference manual and many more are available from our website at http www novatel com support applicationnotes htm GPS Reference Manual Rev 0l 9 Ch
90. part to the United States GPS and the European Union s Galileo positioning systems When complete the GLONASS space segment will consist of 24 satellites in three orbital planes with eight satellites per plane in three orbital planes The satellites are placed into nominally circular orbits with target inclinations of 64 8 degrees and an orbital height of about 19 140 km which is about 1 050 km lower than GPS satellites See also Chapter 5 GLONASS Overview starting on Page 29 Full name is NAVSTAR Global Positioning System A space based radio positioning system which provides suitably equipped users with accurate position velocity and time data GPS provides this data free of direct user charge worldwide continuously and under all weather conditions The GPS constellation consists of 24 orbiting satellites four equally spaced around each of six different orbital planes The system is being developed by the Department of Defence under U S Air Force management See also Chapter 1 GPS Overview starting on Page 9 The shortest distance between any two points along the surface of a sphere or ellipsoid and therefore the shortest navigation distance between any two points on the Earth Also called Geodesic Line NovAtel s Waypoint Software A reference station with known latitude longitude and height coordinates The user may also assign horizontal and vertical standard deviations for these values There can be horizontal vertical or 3 D p
91. quivalents between the SI Syst me Internationale units of weights and measures used in the metric system and those used in the imperial system A complete list of hexadecimal values with their binary equivalents is given in Section 12 5 while an example of the conversion from GPS Time of week to calendar day is shown in Section 12 6 12 1 Distance 1 meter m 100 centimeters cm 1000 millimeters mm 1 kilometer km 1000 meters m 1 nautical mile 1852 m 1 international foot 0 3048 m 1 statute mile 1609 344 m 1 US survey foot 0 3048006096 m 1 inch 25 4 mm 12 2 Volume 1 liter 1 1000 cubic centimeters cc 1 gallon Imperial 4 546 liters 1 gallon US 3 785 liters 12 3 Temperature degrees Celsius 5 9 x degrees Fahrenheit 32 degrees Fahrenheit 9 5 x degrees Celsius 32 12 4 Weight 1 kilogram kg 1000 grams 1 pound 0 4536 kilogram kg GPS Reference Manual Rev 0l 53 Chapter 12 Unit Conversion 12 5 Hexadecimal Binary and Decimal Equivalents Hex Binary Decimal Hex Binary Decimal Hex Binary Decimal Hex Binary Decimal 0 0000 0 4 0100 4 8 1000 8 C 1100 12 1 0001 1 5 0101 5 9 1001 9 D 1101 13 2 0010 2 6 0110 6 A 1010 10 E 1110 14 3 0011 3 7 0111 7 B 1011 11 F 1111 15 Binary Decimal Binary Decimal Binary Decimal Binary Decimal 10000 16 100101 37 111010 58 1001111 79 10001 17 100
92. r a subscription to the OmniSTAR VBS service the ProPak V3 is a high quality receiver with sub meter capabilities The position from the GPSCard in the receiver is used as the L band system s first approximation After the L band processor has taken care of the atmospheric corrections it then uses its location versus the base station locations in an inverse distance weighted least squares solution L band technology generates corrections optimized for the location It is this technique that enables the L band receiver to operate independently and consistently over the entire coverage area without regard to where it is in relation to the base stations 42 2 High and Extra Performance Services The OEMV 3 or ProPak V3 with OmniSTAR High Performance HP service gives you more accuracy than the OmniSTAR VBS or CDGPS services OmniSTAR HP computes corrections in dual frequency RTK float mode within about 10 cm accuracy The XP service is similar to HP but less accurate 15 cm and more accurate than VBS 1 m HP uses reference stations while XP uses clock model data from NASA s Jet Propulsion Laboratory JPL To obtain these corrections your receiver must have an HP or XP subscription from OmniSTAR visit www omnistar com for details lt 1 For optimal performance allow the OmniSTAR HP or XP solution to converge prior to starting any dynamic operation 2 OmniSTAR XP is now available over a wider coverage area GPS Reference Manual R
93. rcular error probable the radius of a circle such that 5096 of a set of events occur inside the boundary A pseudorandom string of bits that is used primarily by commercial GPS receivers to determine the range to the transmitting GPS satellite The 1023 chip C A code repeats every 1 ms giving a code chip length of 300 m which is very easy to lock onto A method established for message transfer between a talker and a listener which includes the message format and the sequence in which the messages are to be transferred Also includes the signalling requirements such as bit rate stop bits parity and bits per character See Ground Control Point GRP The Master Control Station and the globally dispersed Reference Stations used to manage the GPS satellites determine their precise orbital parameters and synchronize their clocks GPS Reference Manual Rev 0l Glossary Controller Area Chapter 15 A rugged serial bus with a protocol that provides services for processes data and Network Bus CAN Bus network management Coordinated Universal Time Course Course Made Good CMG Course Over Ground COG Cross Track Error XTE Cycle Slip Dead Reckoning Destination Differential GPS DGPS GPS Reference Manual Rev 0l This time system uses the second defined true angular rotation of the Earth measured as if the Earth rotated about its Conventional Terrestrial Pole However UTC is adjusted only in incremen
94. red When a satellite signal is lost due to signal masking the signal is typically re acquired within 2 3 seconds after the satellite signal meets the minimum input levels The vehicle dynamics during the masking period are assumed to be less than or equal to 0 5 g acceleration and 100 m s velocity When total signal masking occurs navigation resumes within 3 5 seconds of a Navigation mode criteria being met The receiver is capable of acquiring satellite signals with a minimum input carrier to noise density ratio C N9 to the correlator of 34 dB Hz Once a signal has been acquired the receiver is capable of tracking satellite signals with a minimum input carrier to noise density ratio C No to the correlator of 31 dB Hz GPS Reference Manual Rev 0l 49 OE IGE EM Standards References DX Website addresses are subject to change however they are accurate at the time of posting NOVATEL INC Contact your local NovAtel dealer first for more information To locate a dealer in your area or if the problem is not resolved contact NovAtel Inc directly Customer Service Department 1120 68 Avenue NE Calgary AB Canada T2E 8S5 Phone 1 800 NOVATEL U S amp Canada or 1 403 295 4900Fax 1 403 295 4901 E mail support novatel com Website http www novatel com RTCM STANDARDS REFERENCE For detailed specifications of RTCM refer to RTCM SC104 Recommended Standards for Differential GNSS Global Navigation Satellite Syst
95. requency Antipodal satellites are in the same orbit plane separated by 180 degrees in argument of latitude This is possible because the paired satellites will never appear at the same time in view of an operational receiver that is on the Earth s surface see Figure 13 GLONASS Antipodal Satellites on Page 33 At the time of publication April 2007 four pairs of operational satellites share frequencies 1 Refer to the GLONASS Interface Control Document ICD Version 5 0 Moscow 2002 for more details You can find GLONASS contact information on Page 51 GPS Reference Manual Rev 0l GLONASS Overview Chapter 5 Figure 13 GLONASS Antipodal Satellites A comparison of GPS with GLONASS satellites signals and messages is in Table 2 on Page 35 5 2 Time As stated earlier both GPS and GLONASS satellites broadcast their time within their satellite messages NovAtel s OEMV family of receivers are able to receive and record both time references as well as report the offset information between GPS and GLONASS time Although similar GPS and GLONASS have several differences in the way they record and report time Please see the following sections for information on GPS and GLONASS time as well as on how NovAtel s OEMV receivers are GPS week rollover compliant 5 2 31 GPS Time vs Local Receiver Time All logs output by the receiver report GPS Time expressed in GPS weeks and seconds into the week The time reported is not corrected for loca
96. rol ESD Practices Chapter 13 Where protective measures have not been installed a suitable alternative would be the use of a Portable Field Service Grounding Kit for example 3M Kit 8501 or 8507 This consists of a portable mat and wrist strap which must be attached to a suitable ground A circuit board in a static shielding bag or clamshell may be shipped or stored in a cardboard carton but the carton must not enter a static controlled area such as a grounded or dissipative bench top or repair zone Do not place anything else inside the bag for example repair tags Treat all PCBs and components as ESD sensitive Assume that you will damage the PCB or component if you are not ESD conscious Do not use torn or punctured static shielding bags A wire tag protruding through the bag could act as a lightning rod funneling the entire charge into the components inside the bag e Do not allow chargeable plastics such as binders within 0 6 m of unshielded PCBs e Do not allow a PCB to come within 0 3 m of a computer monitor 13 3 Prime Static Accumulators Table 5 provides some background information on static accumulating materials Table 5 Static Accumulating Materials Work Surfaces formica waxed or highly resistive finished wood synthetic mats writing materials note pads etc Floors wax finished vinyl Clothes common cleanroom smocks personal garments all textiles non conductive shoes
97. rruption of signals can be expected GPS Reference Manual Rev 0l 41 Chapter 9 Multipath 9 1 Multipath Basics Multipath errors are GNSS errors caused by the interaction of the GNSS satellite signal and its reflections as in Figure 15 Multipath is inescapable even with careful setups away from obvious reflectors because of the constantly moving GNSS satellite constellations Antenna hardware solutions are capable of achieving varying degrees of multipath suppression NovAtel s internal receiver solutions are a desirable and practical accompaniment Figure 15 Multipath 9 1 1 Pseudorange and Code Chips 42 Notice in Figure 15 how the signal path d1 d2 is longer than the d3 path This multipath delay the additional time for the signal to travel d1 d2 can also be seen in Figure 19 Comparison of Multipath Envelopes on Page 45 Searching for a GNSS signal uses the mathematical process of correlation Correlation is used to find the relationship between the errors in position and time between the measurements The GPS satellite signal identifies the satellite and provides the positioning timing ranging data satellite status and the corrected ephemerides orbit parameters of the satellite to the users The satellites can be identified either by the Space Vehicle Number SVN or the Pseudorandom Code Number PRN The PRN is used by NovAtel receivers The coarse acquisition C A code is a pseudorandom string th
98. satellites as is the case when both GPS and Galileo are in operation This is particularly important for land based services such as private car navigation where service is mostly required in down town cores and where satellite shadowing is minimised by the combination of the systems The Open Service will be transmitted in the E5a frequency band at 1176 45 MHz 6 1 2 Commercial Service Service providers using the multi frequency commercial services will have the opportunity to give added value to their range of products for which they can charge the end customer and will in turn pay a fee to the Galileo operator The signal will contain data relating to the additional commercial services being offered In return for the fee the Galileo operator will be able to offer certain service guarantees This aspect of service guarantee and the commensurate liabilities is one area where Galileo is significantly differentiated from GPS A key component in achieving this is an independent system within Galileo for monitoring the satisfactory working of the system and informing the end user of this by an integrity signal incorporated in the data stream The main applications for this service concern professional users who are ready to pay for a service guaranteed by the Galileo operator notably in the areas of technical surveys in activities involving customs and excise operations network synchronisation sea fleet management vehicle fleet management an
99. signal loss Though it is possible to use other high quality antenna cables the performance specifications of NovAtel receivers are warranted only when used with NovAtel supplied accessories 1 3 4 3 GNSS System Errors In general GPS SPS C A code single point pseudorange positioning systems are capable of absolute position accuracies of about 1 8 meters or less This level of accuracy is really only an estimation and may vary widely depending on numerous GNSS system biases environmental conditions as well as the GNSS receiver design and engineering quality There are numerous factors which influence the single point position accuracies of any GNSS code receiving system As the following list shows a receiver s performance can vary widely when under the influences of these combined system and environmental biases e Ionospheric Delays The Earth s ionospheric layers cause varying degrees of GNSS signal propagation delay Ionization levels tend to be highest during daylight hours causing propagation delay errors of up to 30 meters whereas night time levels are much lower and may be as low as 6 meters Tropospheric Delays The Earth s tropospheric layer causes GNSS signal propagation delays The amount of delay is at the minimum about three metres for satellite signals arriving from 90 degrees above the horizon overhead and progressively increases as the angle above the horizon is reduced to zero where delay errors may be as much as 50 m
100. signals Combined GPS and GLONASS measurements allow both real time and post processing GNSS applications OEMV based output is compatible with GrafNav post processing software from NovAtel s Waypoint Products Group Visit our website at http www novatel com products waypoint pps htm for details 1 This GLONASS Overview section was originated and reviewed with contributions from Professor Richard B Langley Geodetic Research Laboratory Department of Geodesy and Geomatics Engineering University of New Brunswick Fredericton N B Canada E3B 5A3 http www unb ca GGE 2 Refer to the Russian Space Agency s website at http www glonass ianc rsa ru GPS Reference Manual Rev 0l 29 Chapter 5 GLONASS Overview 5 1 GLONASS System Design As with GPS the GLONASS system uses a satellite constellation to provide ideally GLONASS receiver with six to twelve satellites at most times A minimum of four satellites in view allows a GLONASS receiver to compute its position in three dimensions as well as become synchronized to the system time The GLONASS system design consists of three parts e The Control segment e The Space segment e The User segment All these parts operate together to provide accurate three dimensional positioning timing and velocity data to users worldwide 5 1 1 The Control Segment The Control Segment consists of the system control center and a network of command tracking stations across Russia
101. sing P code A number assigned by the GPS system designers to a given set of pseudorandom codes Typically a particular satellite will keep its PRN and hence its code assignment indefinitely or at least for a long period of time It is commonly used as a way to label a particular satellite An Earth based transmitter designed to mimic a satellite The calculated range from the GPS receiver to the satellite determined by taking the difference between the measured satellite transmit time and the receiver time of measurement and multiplying by the speed of light Contains several sources of error Measurements made using one of the pseudorandom codes on the GPS signals They provide an unambiguous measure of the range to the satellite including the effect of the satellite and user clock biases Parametri Zemli 1990 PZ 90 or in English translation Parameters of the Earth 1990 PE 90 geodetic datum GLONASS information is referenced to the PZ 90 geodetic datum and GLONASS coordinates are reconciled in GLONASS capable NovAtel receivers through a position filter and output to WGS84 A GPS receiver specification which indicates the number of independent hardware signal processing channels included in the receiver design GPS Reference Manual Rev 0l 75 Chapter 15 Reference Satellite Reference Station Relative Bearing Remote Station Residual Root Mean Square RMS Route Rover Station RT 20 Radio Technical Commiss
102. system See also Section 5 1 3 1 GPS and GLONASS Satellite Identification starting on Page 32 c Refer to the GLONASS Interface Control Document ICD Version 5 0 Moscow 2002 for more details You can find GLONASS contact information on Page 51 d GLONASS and GPS use different time systems GLONASS time is referenced to UTC SU the Russian National Etalon time scale whereas GPS Time is referenced to UTC as maintained by the U S Naval Observatory UTC USNO The GLONASS control segment periodically applies a time step to bring the System s time within several hundred nanoseconds of UTC e GLONASS ephemerides are referenced to the Parametry Zemli 1990 PZ 90 or in English translation Parameters of the Earth 1990 PE 90 reference frame The realization of the PZ 90 frame through adopted reference station coordinates has resulted in offsets in origin and orientation as well as a difference in scale with respect to WGS84 used by GPS Relationships between PZ 90 and WGS84 have now been established GPS Reference Manual Rev 0l 35 Chapter 6 6 1 36 This chapter is intended to give you information on the Galileo signals and their use Overview Galileo will be Europe s own global navigation satellite system providing a highly accurate guaranteed global positioning service under civilian control It will be inter operable with GPS and GLONASS the two other global satellite navigation systems A user will be able
103. t can tell which satellites are visible and their Doppler offsets improving TTFF Without this information the receiver must blindly search through all possible satellite PRN codes and Doppler offsets as in a cold start Re acquisition is the resumption of tracking and measurement processing after a brief loss of lock 10 1 OEMV based Products Once satellites are acquired the receiver will normally require another 18 36 seconds to receive broadcast ephemeris data to calculate a position To avoid this delay the receiver saves ephemeris data in its NVM and will use that data if it is less than 2 hours old Table 3 Typical Receiver TTFF for OEMV Based Products Information Available to the Receiver Typical TTFF Approx Approx Aima ac Recent Position Time Ephemeris Cold Start No almanac or no no no no 50s ephemeris and no approximate position or time Warm Start Almanac yes yes yes no 40s approximate position and time no recent ephemeris Hot Start Almanac and recent yes yes yes yes 30s ephemeris saved and approximate position gt lt The TTFF numbers quoted assume an open environment Poor satellite visibility or frequent signal blockage increases TTFF Upon power up the receiver does not know its position or time and therefore cannot use almanac information to aid satellite acquisition To aid in initial positioning or timing you can set an approximate GPS Time using the SE
104. tage of differential positioning is that much greater precision presently as low as 2 mm depending on the method and environment can be achieved than by single point positioning In order for the observations of the base station to be integrated with those of the rover station differential positioning requires either a data link between the two stations if the positioning is to be achieved in real time or else post processing of the data collected by the rover station At least four GPS satellites in view are still required The absolute accuracy of the rover station s computed position will depend on the accuracy of the base station s position rd 1 i Rover Base Figure 5 Example Differential Positioning Setup Reference Description A ProPak V3 receiver for the rover station User supplied NovAtel GNSS antenna User supplied data storage device to COM1 User supplied power supply User supplied radio device to COM2 A ProPak V3 receiver for the base station User supplied laptop PC for setting up and monitoring to COM1 NOOO fP WD GPS Reference Manual Rev 0l GPS Overview Chapter 1 1 3 2 Static vs Kinematic Positioning Static and kinematic positioning refer to whether a GPS receiver is stationary or in motion while collecting GPS data Refer to Chapter 5 of the OEMV Family Installation and Operation Manual for more details on static and kinematic positioning SUPERSTAR II and OEM4 based product manuals also con
105. tain a chapter on positioning modes of operation Portable Document Format PDF manuals are available from our website at http www novatel com support docupdates htm 1 3 8 Real time vs Post mission Data Processing Real time or post mission data processing refer to whether the GPS data collected by the receiver is processed as it is received or after the entire data collection session is complete Refer to Chapter 5 of the OEMV Family Installation and Operation Manual set for more details on post processed and real time positioning OEMV based output is compatible with post processing software from the Waypoint Products Group NovAtel Inc See also our website at www novatel com for details 1 3 4 Performance Considerations 1 3 4 1 Antenna Selection An active antenna is required because its Low Noise Amplifier LNA boosts the power of the incoming signal to compensate for the line loss between the antenna and the receiver NovAtel offers a variety of single and dual frequency GNSS antenna models as indicated in Table 1 below All include band pass filtering and an LNA The GNSS antenna you choose will depend on your particular application Each of these models offer exceptional phase center stability as well as a significant measure of immunity against multipath interference Each one has an environmentally sealed radome The ANT 532 ANT 533 ANT 534 ANT 536 ANT 537 ANT 538 GPS 702L GPS 701GG and GPS 702GG are RoHS compliant
106. tarting with a GPS Time of Week of 51 200 seconds the calculations are done as follows 511200 seconds Day of Week 511200 86400 seconds per day 5 916666667 days Hour 0 916666667 x 86400 3600 seconds per hour 22 0000 hours Minute 0 000 x 3600 60 seconds per minute 0 000 minutes Second 0 000 x 60 seconds per minute 0 000 seconds Therefore 511200 seconds represents day 5 Thursday 22 hours 0 minutes 0 seconds into Friday 12 6 2 Calendar Date to GPS Time Converting a calendar date to GPS Time is calculated as shown in the example below using the calendar date 13 30 hours January 26 2005 Years from January 6 1980 to January 28 2005 Number of days in 25 years 25 years x 365 days year Add one day for each leap year a year which is divisible by 4 but not by 100 unless it is divisible by 400 as every 100 years a leap year is skipped Add days from January 6 to January 27 January 28th is not finished Total days Total number of seconds 9154 days x 86400 seconds day Total number of weeks 790 905 600 seconds 604 800 seconds week Days into week 0 714285 x 7 days week Number of seconds in 5 days 5 days x 86400 seconds day Add number of seconds into the 6th day January 28th 13 5 hours x 3600 seconds hour Total seconds into week The resulting value for GPS Time is Week 1307 480 600 seconds GPS Reference Manual Rev 0l 25 years 9 125 days 7 days 22 days 9 154 days 790 905 600 seconds 13
107. to take a position with the same receiver from any of the satellites in any combination By offering dual frequencies as standard however Galileo will deliver real time positioning accuracy down to the metre range which is unprecedented for a publicly available system It will guarantee availability of the service under all but the most extreme circumstances and will inform users within seconds of a failure of any satellite This will make it suitable for applications where safety is crucial such as running trains guiding cars and landing aircraft The first experimental satellite part of the so called Galileo System Test Bed GSTB was launched in the second semester of 2005 The objective of this experimental satellite is to characterize the critical technologies which are already in development under European Space Agency ESA contracts Thereafter up to four operational satellites will be launched in the 2007 2008 time frame to validate the basic Galileo space and related ground segment Once this In Orbit Validation IOV phase has been completed the remaining satellites will be installed to reach the Full Operational Capability FOC in 2010 The fully deployed Galileo system consists of 30 satellites 27 operational 3 active spares positioned in three circular Medium Earth Orbit MEO planes in 23616 km altitude above the Earth and at an inclination of the orbital planes of 56 degrees with reference to the equatorial plane Once this
108. ts of one second The time zone of UTC is that of Greenwich Mean Time GMT The horizontal direction in which a vessel is to be steered or is being steered the direction of travel through the air or water Expressed as angular distance from reference North either true magnetic compass or grid usually 000 north clockwise through 360 Strictly the term applies to direction through the air or water not the direction intended to be made good over the ground see Track Made Good Differs from heading The single resultant direction from a given point of departure to a subsequent position the direction of the net movement from one point to the other This often varies from the track caused by inaccuracies in steering currents cross winds etc This term is often considered to be synonymous with Track Made Good however Course Made Good is the more correct term The actual path of a vessel with respect to the Earth a misnomer in that courses are directions steered or intended to be steered through the water with respect to a reference meridian this will not be a straight line if the vessel s heading yaws back and forth across the course The distance from the vessel s present position to the closest point on a great XTE Circle line connecting the current waypoint coordinates If a track offset has been specified in the receiver SETNAV command the cross track error will be relative to the offset track great circle line
109. tude longitude height HTDOP Uncertainty of 2 D and time parameters latitude longitude time HDOP Uncertainty of 2 D parameters latitude longitude VDOP Uncertainty of height parameter TDOP Uncertainty of clock offset parameter The change in frequency of sound light or other wave caused by movement of its source relative to the observer Theoretical Doppler The expected Doppler frequency based on a satellite s motion relative to the receiver It is computed using the satellite s coordinates and velocity and the receiver s coordinates and velocity Apparent Doppler Same as Theoretical Doppler of satellite above with clock drift correction added Instantaneous Carrier The Doppler frequency measured at the receiver at that Doppler Frequency epoch A signal processing strategy which uses a measured Doppler shift to help a receiver smoothly track the GPS signal to allow more precise velocity and position measurement A mathematical technique comparing observations by differencing between receiver channels and then between the base and rover receivers Carrier phase ambiguities which are differenced between receiver channels Carrier Phase and between the base and rover receivers They are estimated when Ambiguitya double difference mechanism is used for carrier phase positioning Sometimes double difference ambiguity or ambiguity for short This is a coordinate ordinate system which has the X coordinate i
110. ual frequency civil users many of who needed a civil code to replace semi codeless tracking e Scientific earthquakes volcanoes continental drift weather e Cadastral and construction land survey e Guidance and control mining construction agriculture e Land and offshore land and mineral exploration Marine survey and construction NovAtel s GNSS Modernization NovAtel s OEMV 3 GNSS engine is a triple frequency board that includes L2C GLONASS measurements and hardware support for the future L5 GPS frequency It is a drop in replacement for the OEM4 G2 with compatible commands and logs The EuroPak L1L5E5a receiver offers superior 16 channel tracking of GPS L1 L5 Galileo L1 E5a and SBAS signals See also Section 6 2 LIL5E5a Receiver on Page 38 While providing today s leading edge technology the WAAS G II has the added advantage of expandability for the future With the capability to hold up to 12 Euro form factor cards in three independent receiver sections the WAAS G II is ready to support additional receiver cards for tracking such signals as GPS L5 and L2C Galileo and GLONASS As a result the WAAS G II is ready for the future in the world s wide area reference networks GPS Reference Manual Rev 0l 39 Chapter 8 L5 Overview The United States plans to implement a third civil GPS frequency L5 at 1176 45 MHz beginning with the first Block IIF NAVSTAR GPS satellite to be launched in 2007 This frequency is located with
111. umulated Doppler Range Accumulated Delta Range Automatic Gain Control Authentication Key Alarm Limit Alternate Binary Offset Carrier American Satellite Aircraft Power Conditioner Aeronautical Radio Navigation Services Antenna Reference Point Anti Spoofing American Standard Code for Information Interchange Application Specific Integrated Circuits Automatic Vehicle Location Binary Coded Decimal Borland Database Engine Black Diamond System Broadband Fiber Source Bureau l International de l Heure Built In Self Test Built In Test Binary Numerical Representation Binary Offset Carrier Bits per Second Bi Phase Shift Key Baseband Signal Generator Conventional Terrestrial System BIH defined Bandwidth Coarse Acquisition Code Controller Area Network Coherent Adaptive Subcarrier Modulation Continuous Built In Test Cubic Centimeters Command Control and Intelligence Technical Test Clock Drift Compact Disc Change Directory Canada Wide Differential Global Positioning System Code Division Multiple Access Cellular Digital Packet Data Control and Display Unit GPS Reference Manual Rev 0l 59 Chapter 14 60 CE CEP CF CFGP CISPR CMR C No CoCom COG COGO COSPAS CPLD CPU CR CRC CRR CS CSA CSIC CTP CTS CTS CW dB dBm DC DCD DCE DCO DDS DGNSS DGPS DHCP DL DLL DoD DOP DPB DR DRAM DRMS DSP DSR DTE DTR Acronyms Conformit Europ enne Circular Error Probable Compact
112. ver all three beams but the user system must select the proper beam frequency The beams have overlaps of several hundred miles so the point where the frequency must be changed is not critical The L band frequency can be changed using the ASSIGNLBAND command Refer to the OEMV Family Firmware Reference Manual or to Volume 2 of the OEM4 User Manual set The North American OmniSTAR Network currently consists of ten permanent base stations in the Continental U S plus one in Mexico These eleven stations track all GPS satellites above 5 degrees elevation and compute corrections every 600 milliseconds The corrections are sent to the OmniSTAR Network Control Center NCC in Houston via wire networks At the NCC these messages are checked compressed and formed into packets for transmission up to the OmniSTAR satellite transponder This occurs approximately every few seconds A packet will contain the latest corrections from each of the North American base stations All of the eastern Canadian Provinces the Caribbean Islands Central America south of Mexico and South America is covered by a single satellite AM Sat A single subscription is available for all the areas covered by this satellite OmniSTAR currently has several high powered satellites in use around the world They provide coverage for most of the world s land areas Subscriptions are sold by geographic area Any Regional OmniS TAR service center can sell and activate subscriptions f
113. verview 32 5 1 3 1 GPS and GLONASS Satellite Identification The GLONASS satellites each transmit on slightly different L1 and L2 frequencies with P code on both L1 and L2 and with C A code at present only on L1 GLONASS M satellites reportedly transmit the C A code on L2 Every GPS satellite transmits the L1 frequency centered at 1575 42 MHz The GPS satellites are identifiable by their Pseudorandom Code Number PRN with a NovAtel receiver Unlike GPS all GLONASS satellites transmit the same code at different frequencies They derive signal timing and frequencies from one of three on board cesium atomic clocks operating at 5 MHz For example L1 1602 MHz n x 0 5625 MHz where n the frequency channel number n 0 1 2 and so on It means that satellites transmits signals on their own frequency separated by multiples of 0 5625 MHz or 562 5 kHz from the frequency of other satellites See also Figure 12 below n 1 n 5 n io MHz Al Ges satellites use L1 1602 5625 L1 1604 8125 L1 1607 625 an L1 frequency centered at GLONASS satellites each have a unique or an antipodal frequency 1575 42 Mhz For GLONASS L1 L1 1602 MHZ n x 0 5625 MHz Figure 12 GPS and GLONASS L1 Frequencies The signals are right hand circularly polarized like GPS signals and have comparable signal strength GLONASS accomplishes system operation 24 satellites and only 12 channels by having antipodal satellites transmit on the same f

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