RT-Base RT-Base User Manual - Industrial Measurement Solutions
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1. RT Base User Manual Confidently Accurately Oaxrs Legal Notice Information furnished is believed to be accurate and reliable However Oxford Technical Solutions Limited assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or patent rights of Oxford Technical Solutions Limited Specifications mentioned in this publication are subject to change without notice and do not represent a commitment on the part of Oxford Technical Solutions Limited This publication supersedes and replaces all information previously supplied Oxford Technical Solutions Limited products are not authorised for use as critical components in life support devices or systems without express written approval of Oxford Technical Solutions Limited All brand names are trademarks of their respective holders Copyright Notice Copyright 2007 Oxford Technical Solutions Revision Document Revision 070316 See Revision History for detailed information Contact Details Oxford Technical Solutions Limited 77 Heyford Park Upper Heyford Oxfordshire OX25 5HD England Tel 44 0 1869 238 015 Fax 44 0 1869 238 016 http www oxts co uk mailto info oxts co uk a Oxford Technical Solutions RT Base User Manual Czxzz Table of Contents Introduction O2. as part of its data You have to use a modem that can transmit all the data sent The settings of the data sent from the RT Base are given in Table 8 The radio modem must use these settings or the data will not be transmitted correctly Revision 070316 Oaxrs Table 8 Serial Port Settings for RT Base transmissions Parameter Setting Baud Rate 9600 Data Bits 8 Parity None Stop Bits 1 The Power Output pin of the GPS Configuration connector supplies between 11V and 15V depending on whether the internal batteries are charging or flat If you are using a standard modem cable then take care in case this power damages the modem You will probably have to make a special cable so that the signals and power from this connector can go to the radio modem correctly Note that this output is not fused individually shorting the power on this connector will blow the main fuse in the RT Base You are recommended to always make connections to the GPS Configuration port when the power 1s off When using an external modem it is not possible to close the top of the RT Base Without the top closed the RT Base is not rated to IP65 and protection from moisture is required EJ Oxford Technical Solutions RT Base User Manual Czxzz Special Configuration of the RT Base Sometimes it is necessary to store more than one position for the base station antenna For example the RT Base may be used at more than one location The software in t
3. is sensitive to electro static discharge ESD e The display may go blank when ESD occurs to some parts of the RT Base e Other components in RT Base continue to operate correctly even if diplay appears blank due to ESD j Oxford Technical Solutions RT Base User Manual Czxzz Discussion on Repeatability Differential Corrections for GPS change the way that a GPS receiver works When using Differential Corrections the GPS receiver is effectively measuring the position relative to the base station not the absolute position on earth This leads to several effects that the user should be aware of 1 H the base station antenna is moved then the remote GPS receivers move too It is important to put the GPS antenna in a location where it cannot move or be moved See Figure 6 2 The base station has to measure its own position If the base station gets this position wrong then the remote GPS receivers will also be wrong They will be correct relative to the base station but they will have the same error on the earth that the base station has This is important when turning the RT Base off and on again See Figure 7 Figure 6 Shifting Base Station Antenna Example Shifting the base station antenna shifts the remote position as well The problem of shifting the antenna typically occurs when The tripod is knocked over and picked up again It is hard to get the antenna back to the same location accurate to lcm If th
4. it computes position and time Figure 1 Differential GPS Overview e Oxford Technical Solutions RT Base User Manual Czxzz For RTK Real Time Kinematic Carrier Phase measurements the principle is the same but the GPS in the car also has to figure out the difference in the number of carrier phase cycles between the RT Base and the car The RT Base measures the carrier phase of the signals from each satellite and transmits it to the car Differential GPS works in real time because the corrections from each satellite vary slowly and predictably The GPS in the car uses a model to predict the error from each satellite It can update its model when the radio link transmits new data It is not necessary for the GPS in the car to wait until the radio has transmitted the correction before it outputs its latest value Table 1 below lists information about each of the different correction types that are available Table 1 Summary of Differential Correction Types Max Age Packet RT Base Correction Measurement Accuracy f 2 typical Type Model RT Base 20 s 1 Differential L1 Pseudo Range 45cm 60s RTCAI RT Base 2 Ll L1 Carrier Phase 20cm 30s mm MU RT Base 2 L1 L2 L1 L2 Carrier Phases 2cm 30s RTCAOBS a a Note 1 Using the smoothing of the Inertial Navigation System the RT3000 can achieve 40cm of position accuracy using Differential GPS Note 2 The RT Base also transmits the RTCAREF packet For Pseudo Range not ca
5. 050919 14ap or later 070316 Updated images incl different radio modems Revision 070316 ie
6. Operation Follow these steps to operate your RT Base unit correctly Charging Before using the RT Base for the first time charge the battery in the unit by connecting it to the mains A switch next to the mains plug can be used to turn the mains power on or off The RT Base takes about 2 hours to fully charge Choosing a Suitable Location For correct operation of the RT Base it is essential to locate the GPS antenna in a location where it has a full view of the sky down to an elevation of 10 degrees in all directions It must also be away from reflective objects like buildings and trees Figure 3 RT Base Location away from Buildings Trees and Reflective Objects 2 bu ta bb x h h af The RT Base unit should not be left in direct sunlight or the internal temperature may exceed the specification The temperature range of the unit is restricted because of the internal battery Revision 070316 Cxzsz Connecting the RT Base System Connect the GPS Antenna to the tripod or to a secure pole The mounting should ensure that the antenna does not move including in wind or gusts such as when a car drives past Connect the GPS Antenna Cable to the GPS Antenna and to the GPS Antenna input on the RT Base unit Ensure that the link wire is fitted between the two 9 way D type connectors to activate the internal radio see section on Using an External Radio for more details Note Never extend or shorten the GP
7. S Antenna Cable The loss in the cable is carefully matched to the GPS Receiver and lengthening or shortening the cable will reduce the performance of the RT Base system Connect the GPS Cable to the GPS Antenna TNC on the front of the RT Base Note Never connect the GPS Antenna to the Radio Aerial connector The use of two TNC connectors is required since they have much better ground properties compared to BNC connectors The Radio Aerial output has a high power signal that may damage the GPS Antenna Locate the Radio Modem Aerial at least 2m away from the GPS Antenna Clip the Radio Modem Aerial on a metal object such as the roof of a car Connect the Radio Modem Aerial to the Radio Aerial connector on the RT Base unit Figure 4 RT Base Connections Figure 4 above shows the connections for the GPS Antenna and the Radio Aerial Ey Oxford Technical Solutions RT Base User Manual Czxzz Using the RT Base System After turning on the RT Base unit it follows the sequence in Figure 5 below Figure 5 RT Base Flowchart Booting sat 0 Dev ID 030611 14ap A Restore Save a Searching sat 3 GPS Pos Set To Load Searching sat 0 Dev ID 030611 14ap Averaging sat 5 Time Remaining 2 58 RTCA OK sat 8 Lon 1 2345678 RTCA OK sat 8 Lat 51 2345678 Display Rotates RTCA OK sat 8 Alt 123 456m Longitude of the base station s ante
8. arranty Oxford Technical Solutions Limited warrants the RT Base products to be free of defects in materials and workmanship subject to the conditions set forth below for a period of one year from the Date of Sale Date of Sale shall mean the date of the Oxford Technical Solutions Limited invoice issued on delivery of the product The responsibility of Oxford Technical Solutions Limited in respect of this warranty is limited solely to product replacement or product repair at an authorised location only Determination of replacement or repair will be made by Oxford Technical Solutions Limited personnel or by personnel expressly authorised by Oxford Technical Solutions Limited for this purpose In no event will Oxford Technical Solutions Limited be liable for any indirect incidental special or consequential damages whether through tort contract or otherwise This warranty is expressly in lieu of all other warranties expressed or implied including without limitation the implied warranties of merchantability or fitness for a particular purpose The foregoing states the entire liability of Oxford Technical Solutions Limited with respect to the products herein Revision 070316 u Cxzsz Conformance Notices The RT Base complies with the radiated and conducted emission limits Class B of FCC CFR 47 Class B of Part 15 of the FCC rules with the conducted emissions limits for Class A of EN 61326 with the radiated emissions limits for Cl
9. ass B of EN 61326 and immunity limits of EN 61326 These limits are designed to provide reasonable protection against harmful interference in a residential installation This equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with the instructions may cause harmful interference to radio communications However there is no guarantee that interference will not occur in a particular installation If this equipment does cause harmful interference to radio or television reception which can be determined by turning the equipment off and on the user is encouraged to try to correct the interference by one or more of the following measures Re orient or relocate the receiving antenna Increase the separation between the equipment and the receiver It is occasionally possible for the LCD display of the RT Base unit to become black following electrostatic discharge however the RT Base continues to work correctly The RT Base incorporates a GPS receiver Any GPS receiver will not be able to track satellites in the presence of strong RF radiations within 70 MHz of either GPS frequencies 1575 MHz L1 1228 MHz L2 The RT Base conforms to the requirements for CE Regulator Testing Standards e EN55022 e EN61000 4 2 e EN61000 4 3 e EN61000 4 4 e EN61000 4 5 e EN61000 4 6 e EN61000 4 11 FCC CFR 47 Class B l i Oxford Technical Solutions RT Base User Manual Qaxrs
10. e RT Base is used one day packed up then returned to the same location the next day It is very hard to replace the tripod in the same location It is better to have a pole that is fixed to the ground if you intend to use the same surveyed location on several days Revision 070316 Ea Figure 7 Averaging to a Different Position Example gt Averaging to different positions leads to different positions on Q lt the track lt The problem of averaging to a different position happens each time that the RT Base goes through its averaging process There is nothing magical about the RT Base that allows it to get its own position accurate to 2cm or better It is subject to the same errors that all GPS receivers have and can only average its position to about 1 8m CEP If the user is prepared to wait a long time typically more than 24 hours then GPS is able to improve the accuracy of the base station antenna so it is accurate to 2cm or better However since the timescale for this is long it is not usually practical except for permanent installations Even when you have a permanent installation it is not required since all it does is allows you to relate your measurements to a surveyors measurements and this is rarely required To overcome the problem of averaging the save restore feature of the RT Base should be used When using the Save Restore feature the RT Base will save the position where it last averaged and then use t
11. ecified 77C0002B Power Cable Internal Radio Link fit to use internal radio RT Base User Manual RT Base Quick Guide Table 5 Summary of the RT Base Components with Futaba radio Qty 1 Description RT Base Unit GPS C006 15m GPS Antenna Cable GPS 702 GG GPS Antenna Radio Antenna SMA connector and Magnetic Base 2m SMA SMA Antenna Extension Cable 5m SMA SMA Antenna Extension Cable TNC SMA Adaptor fitted to one of the Radio Antennas Lightweight Tripod IEC US Mains Lead 77C0002B Power Cable 14C0045A RT3000 Futaba Radio Cable Internal Radio Link fit to use internal radio Futaba Radio Modem for remote vehicle RT Base User Manual RT Base Quick Guide a Oxford Technical Solutions RT Base User Manual Cbxzz Figure 2 RT Base Components Revision 070316 C xzsz Specification The technical specification of the RT Base unit is shown in Table 6 below Table 6 Technical Specification except Radio Modem Parameter Specification Mains Power 110 240 V AC 50 60Hz 3A Max Battery 12V 7Ah Sealed Lead Acid Charge Time 2 hours Operating Time gt 10 hours Operating Temperature 0 to 50 C Charge Temperature 10 to 40 C Environment IP65 with lid closed Relative Humidity 95 non condensing Corrections RTCA Differential L1 L2 Frequency 1 Hz Format RS232 Dimensions 486 x 392 x 192 mm Weight 12 6 kg EJ Oxford Technical Solutions RT Base User Manual Czxzz W
12. he RT Base cannot do this and the extra positions have to be stored elsewhere and then programmed to the RT Base using a computer Setting the Base Station Position If you want to use a previously computed position to match earlier surveys or work and this is not the position saved in the RT Base you can follow the procedure here 1 Remove the Link Cable that connects the Radio Configuration connector to the GPS Configuration connector Connect a Null Modem Serial cable between a PC COM Serial Port and the GPS Configuration connector 2 Run a serial port application such as Hyperterminal Configure the communications for 9600 baud 8 data bits no parity 1 stop bit no handshaking and no flow control same as Table 8 above 3 The RT Base may be sending some undecipherable data over this port these are the Differential Corrections Ignore the data sent from the RT Base 4 Type the following commands FIX NONE FIX POSITION XX XXXXXXXX VV VVVVVVVV 222 2224 where XX XXXXXXXX is the Latitude in degrees yy yyyyyyyy is the Longitude in degrees and zzz zzz is the Altitude in degrees You should enter at least 8 decimal places for the Latitude and Longitude and three decimal places for the Altitude It is often difficult to type these correctly especially since the RT Base will be sending data all the time It is usually easier to type them into an editor such as Notepad and then paste them into the serial por
13. his next time instead of averaging again This way the error is the same each time and the repeatability is perfect You must remember to put the antenna in the same location each time accurate to lcm or better when using the Save Restore feature Ey Oxford Technical Solutions RT Base User Manual Czxzz Using an External Radio It is possible to disable the internal radio and use an external radio instead This is useful if you need to use the RT Base in several countries and different radios are required to conform to the local licensing laws On the RT Base panel are two 9 way D type connectors Radio Configuration and GPS Configuration These are linked to activate the internal radio To use an external radio disconnect the link wire the GPS Configuration connector is wired as a standard 9 way D type connector with the exception of the ring pin which has power on it Table 7 gives the pin connections for the GPS Configuration connector Table 7 Pin Connections of the GPS Configuration connector Pin Direction Signal 1 N C 2 In Receive 3 Out Transmit 4 N C 5 Out Ground 6 N C 7 N C 8 N C 9 Out Power from internal batteries To use the internal radio replace the link cable The RT Base does not use the hardware handshake lines so it is necessary to use a modem that does not need these lines You cannot use a modem that requires software handshaking since the data on the RT Base will include the XON and XOFF characters
14. nna Latitude of the base station s antenna Altitude of the base station s antenna Revision 070316 EI Cxzsz Step 1 The RT Base unit boots the GPS receiver Step 2 The GPS receiver starts searching for satellites This normally takes about 90s but can take up to 20 minutes if the unit has been turned off for a long period of time or has been moved a significant distance since last time it was used The number following the sat counts the number of satellites being tracked Step 3 Once the GPS receiver has found its position it averages the position for three minutes This does not give a very repeatable position For repeatable performance the averaged position should be saved and restored next time To use the Restore Save button you must have the GPS Antenna in exactly the same location ideally to 2mm or better as when the position was saved Once the Position Averaging has started you cannot use the Restore feature any longer Turn the RT Base off and on again if you need to use the Restore feature Step 4 In Step 4 the RT Base unit starts transmitting corrections the radio will be inactive until now The display shows the Latitude Longitude and Altitude of the location of the GPS Antenna Once at Step 4 press the Restore Save button to save this location This will overwrite the last saved location and can be restored next time the RT Base unit is started ESD notice e The LCD display
15. nse free in USA Brazil Freewave Canada Futaba 2 4 GHz band 10 mW maximum 2 km License free in Japan e Oxford Technical Solutions RT Base User Manual Czxzz Scope of Delivery Table 3 Table 4 and Table 5 list all the items that are delivered with an RT Base and the respective radio modem The customer must check that the radio can be used without a license or obtain a suitable license before using the RT Base Oxford Technical Solutions cannot be held responsible for using this equipment illegally without the correct radio license Table 3 Summary of the RT Base Components with SATEL radio Qty Description 1 RT Base Unit 1 GPS C006 15m GPS Antenna Cable 1 GPS 702 GG GPS Antenna 1 SATEL Satelline 3 ASd Radio Modem for remote vehicle 2 Radio Modem Aerial Antenna with 3m cable and Magnetic Mount 1 Lightweight Tripod 1 IEC Mains Cable UK EU and US style plugs can be specified 1 77C0002B Power Cable 1 Internal Radio Link fit to use internal radio 1 RT Base User Manual 1 RT Base Quick Guide Revision 070316 Ea Table 4 Summary of the RT Base Components with Freewave radio Qty 1 Description RT Base Unit GPS C006 15m GPS Antenna Cable GPS 702 GG GPS Antenna Freewave FGR 115RC 900MHz Radio for remote vehicle 14C0044B Freewave Radio Cable Car Antenna short with 20ft cable Base Station Antenna long with 20ft cable Lightweight Tripod IEC Mains Cable UK EU and US style plugs can be sp
16. rrier phase Differential GPS the corrections can be up to 60s old depending on the GPS in the car For RTK corrections 20cm and 2cm the corrections can be up to 30s old again depending on the GPS in the car Features The RT Base is a self contained unit that includes e The Base Station GPS receiver e Battery suitable for over 12 hours of operation e Radio Modem e Mains Power Supply and Battery Charger Revision 070316 Ea Cxzsz e GPS Antenna 15m Cable and Tripod e Radio Modem Aerial Cable and Magnetic Mount The RT Base also includes a Remote Radio Modem and Antenna for use on the vehicle The Radio Modem in your RT Base will be factory configured for use in a particular country or territory Typically the radio can transmit between 2 km and 5 km line of sight Trees buildings hills and other obstructions limit the range that can be used The RT Base is also suitable for use as a general base station for other products such as the Datron MicroSAT The RT Base transmits corrections in RTCA format accepted by many GPS receivers Table 2 Overview of different radios Radio Specification 380 480 MHz band up to 1 W typically 5 km License free bands SATEL available for many European countries Radio will typically cover 8 bands with 25 kHz channel spacing 869 MHz band up to 500 mW typically 2 km License free across most of poles European Union 900 MHz band up to W typically gt 10 km Lice
17. t application 5 Check on the RT Base display that the position you have requested has been received correctly and that the display matches the values you have entered You can save this location to the RT Base by pressing the Save Restore button on the RT Base Otherwise the previously saved position will remain in the RT Base but the new location will be used until power off Revision 070316 Ea Cxzsz To use the RT Base immediately you need to reconnect the Link Cable between the Radio Configuration and GPS Configuration connectors This must be done very carefully if the power is left on since it is possible to short between Pin 9 of the GPS Configuration connector and the connector chassis this will blow the internal fuse It is recommended to save the new location to the RT Base turn off the RT Base connect the Link Cable turn the RT Base on again and press the Save Restore button to restore the new location Saving the RT Base Position You can save the RT Base Position by writing down the Latitude Longitude and Altitude values that are displayed in the LCD display You should write down all 8 decimal places for the Latitude and Longitude a Oxford Technical Solutions RT Base User Manual Czxzz Revision History Table 9 Revision History Revision Comments 030617 Initial Version 051116 Added Repeatability Discussion External Radio connection external configuration of position requires Software Dev Id
18. verview Features Scope of Delivery 7 Specification 10 Warranty II Conformance Notices 12 Regulator Testing Standards 12 Operation 13 Charging 13 Choosing a Suitable Location 13 Connecting the RT Base System 14 Using the RT Base System 15 ESD notice 16 Discussion on Repeatability 17 Using an External Radio 19 Special Configuration of the RT Base 21 Setting the Base Station Position 21 Saving the RT Base Position 22 Revision History 23 Revision 070316 Hi Oaxrs Introduction The RT Base is a GPS Base Station suitable for transmitting Differential corrections to the RT3000 and other products that use GPS The position accuracy of Differential and RTK GPS receivers is improved when using the RT Base Two models of the RT Base exist the RT Base 20 can supply L1 corrections suitable for 20cm positioning and the RT Base 2 can supply L1 L2 corrections suitable for 2cm positioning Both models are identical in their operation The RT Base is available with several different radio options Different radios are required for license free operation in different countries Overview Figure 1 below gives an overview of how Differential GPS works The information from each satellite is measured by both the RT Base and by the GPS in the car The RT Base works out the error in the satellite s information and transmits it to the car using a radio link The GPS in the car then applies the correction to each satellite s measurement before
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