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1. euenire 10 1 GRSGWHON SS i aceti ordo toe o m Eier et 52 10 2 TINI EGDESGIODIL 15 dcn Deer eb Yet ocu de 53 teet Real Time Kinematic GPS System Via the Internet 10 3 GPS Applet ControllBr ioi ore ERR oet err ees 54 10 4 Communicate with the Receiver sssseessussssss 55 10 4 1 Fix Master Receiver Location susssss 56 10 4 2 Logging Master Receiver Data 56 10 4 3 Set DGPS TImIBOUL i ort e v Te RENE 57 10 4 4 Receive Data from Master Receiver 57 10 4 5 Logging Rover Receiver Data sss 58 10 4 6 Display Rover Location esesseseeeeeeese 58 10 4 7 Manually Enter Command suse 59 10 5 Editing the GPS Applet Controller sssssss 60 10 6 Accuracy of the Computed Location sssssuuse 60 11 Thesis Promotion Mm 62 11 1 WBDSIIB oe o ex o REIR ERR RUE eom xU RE ER 62 11 2 Promotional OD 45g ce es ehe ERE ub ee See eee eats 63 12 Further Development ccceceeeeeeeeeeeeeeaeeeeeeeeeeeeeseseeeeeeneenees 64 12 1 Additional Serial port and Address space 64 12 2 Host Internet Server sssssssssssssseene 65 12 3 Display Features cose vtto cts eroe ER ERE EE LEER PUE 65 12 4 Further Experimentation Lseseeeeeeeesesess 65 12 5 Remove Unnec
2. 11 3 2 Transmission Control Protocol Internet Protocol TCP IP 14 4 Introduction to smartGPS TINI board eese 4 1 TINI board hardware details Specifications 16 4 1 1 The TINI Chip set sese 16 4 1 2 The TINI Runtime Environment 16 4 1 3 Supported Applications Programs Interfaces APlIs 18 4 1 4 The TINI Java Virtual Machine ssss 18 4 1 5 TINI System Architecture ssssssesssssssses 18 4 1 6 TINI Software Development sssssssesssse 19 4 1 7 Compiling and Running in Java Code on TINI 20 4 2 DGPS and RTK using smartGPS ssssssssuss 20 4 3 smartGPS User Interface sessessssssesesee 21 4 4 Flow Diagram of User Diagram sese 22 5 Introduction to Java programming eee 5 1 Object Oriented Language sssssssssseeseesesses 23 52 Tradeoffs text ea tye tac ee nee cede ne e ED EIS 23 5S3 NetWork Savvy iiie ce tdi ceived Au cU ERR 24 5 4 High Performance eseseeseeeeeeseee 25 23 A Real Time Kinematic GPS System Via the Internet 10 Possible applications cccceceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeaeeeeeeeaeee 6 1 Courier Shipment Tracking Services sss 26 6 2 Allocation of Engineering Res
3. Distance Velocity x Time Distance between satellite amp receiver Speed of light x Signal travel time But in order to calculate the distance between them how can we be sure they both have the synchronized clock We can t That is why beside the latitude longitude and altitude we have one more unknown the GPS receivers clock error totally four unknowns Figure 1 2 The relative size of each sphere Obviously four equations can solve four unknowns Similarly a GPS receiver can use four or more satellites to calculate these unknowns By precisely calculate these distances relative to each other only one possible point can intersect as shown in the diagram above and therefore able to find the exact GPS receiver position ad A Real Time Kinematic GPS System Via the Internet 2 2 GPS satellite signals We know the satellites are transmitting signals using L1 and L2 microwave frequencies but what sorts of signals are being sent Three different signals are sent The first two are binary codes are for military users the P code and civilians the C A code The third signal is a navigation message which is available to all users The purpose of the navigation message is to let the GPS receiver know the satellite is in good condition so the signals can be used in confidence The GPS receiver then used a specialized computer to calculate its location based on these satellite signals The re
4. Packet size Packet travel time Packet error rate 256 bytes 1 1 ms 0 00 512 bytes 1 5 ms 0 00 1460 bytes 2 6 ms 0 00 For a UNSW University Node to Cable modem University Node to Cable Modem UDP Unicast connection From UNSW Residential college 129 94 199 101 100Mbps To Optus Cable modem Kingsford Sydney 203 164 51 563 512kbps Packet size Unicast speed Packet travel time Packet error rate 256 bytes 0 77 Mbps 26 5 ms 14 7 512 bytes 0 84 Mbps 48 9 ms 42 1 1460 bytes 1 94 Mbps 60 1 ms 50 6 University Node to Cable modem TCP IP connection From UNSW Residential college 129 94 199 101 100Mbps To Optus Cable modem Kingsford Sydney 203 164 51 563 512kbps Packet size Packet travel time Packet error rate 256 bytes 75 ms 0 00 512 bytes 86 ms 0 00 1460 bytes 102 ms 0 00 47 ud A Real Time Kinematic GPS System Via the Internet For a 56kbps modem to 56kbps modem 56kbps modem to 56kbps modem UDP Unicast connection From ihug 56kbps modem Kensington Sydney 203 173 128 88 33 6kbps To ihug 56kbps modem Randwick Sydney 203 173 131 70 56 6kbps Packet size Unicast speed Packet travel time Packet error rate 256 bytes 0 04 Mbps 45 7 ms 25 496 512 bytes 0 07 Mbps 61 3 ms 39 296 1460 bytes 0 15 Mbps 75 0 ms 67 196 56kbps modem to 56kbps modem TCP IP connection From ihug 56kbps modem Kensington S
5. or int i 0 i lt 6 latitudeSD i data fileReadLine charAt 76 1i 82 A Real Time Kinematic GPS System Via the Internet for rnt tS 0 EGE Ep x longitudeSD i data fileReadLine charAt 83 1 for int i 0 i lt 6 itt heightSD i data fileReadLine charAt 90 1 For int i 0 i lt 15 itt latitudeValue latitudeValue latitude i for int i 0 i 15 i longitudeValue longitudeValue longitude i For int i OF i 7 145 4 heightValue heightValue height i For int i 0 i lt 6 itt latitudeSDValue latitudeSDValue latitudeSD i for int i 0 i lt 6 itt longitudeSDValue longitudeSDValue longitudeSD i for int x 0 i 6 itt heightSDValue catch IO System out println Error else if String command labelOne setText labelTwo setText labelThree setText labelFour setText labelFive setText labelOne setText labelTwo setText labelThree setText labelFour setText labelFive setText labelSix setText Rover Receiver location is listed below labelSeven setText e g latitudeData setText Latitude latitudeValue longitudeData setText Longitude heightData setText Height latitudeSDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard D
6. Control master receiver Fix Master Receiver location P Set DGPS timeout Submitted log com2 RTCAREF ontime 10 Note RTCA Standard Format Data Logs Binary 56 f A Real Time Kinematic GPS System Via the Internet 10 4 3 Set DGPS Timeout The DGPSTIMEOUT command allows the reference station to set the delay by which it will inhibit utilization of new ephemeris data in its differential corrections This delay ensures that the remote receivers have had sufficient time to collect updated ephemeris data as well Command DGPSTIMEOUT dgps delay ephem delay Pee Applet GPSCard APPLET CONTROLLER Control master receiver Fix Master Receiver location Logding Master Receiver data Set DGPS timeout Submitted dapstimeout 2 300 Since this thesis project is dealing with Real Time Kinematics therefore only 2 seconds of delay is given to rover stations to collect updated ephemeris After the delay period is passed the reference station will begin using new ephemeris data 10 4 4 Receive Data from Master This command is used to set the GPSCard s COM port command interpreter for acceptance of various data formats Once initialized the rover GPSCard receiver will operate in single point mode until the differential message are received If data is lost the GPSCard will revert to single point positioning until the pseudorange correction message are restored Command ACCEPT p
7. A Real Time Kinematic G PS system viathe Internet a Au Andy Ming Yu 2248819 tup e Ying Tsz To Donald 2247089 iag Bachelor of Engineering oo Submission Date 5 November 2002 dr ees A Real Time Kinematic GPS System Via the Internet Abstract Real Time Kinematic RTK is a high precision GPS based positioning technique that requires raw carrier phase data to be transmitted from a master GPS receiver to the rover GPS receiver via a data link with very low latency This data link could be appears in different forms such as GSM GPRS Internet or simply a Serial cable Each of them has its own advantages and disadvantages Internet is chosen as the data link between the GPS receivers in this thesis project Hence investigation would be performed on the protocols and hardware for using the Internet to deliver such data to the rover receiver This document outlines the background theory concepts and testing of the Real Time Kinematic System ad A Real Time Kinematic GPS System Via the Internet Table of Contents 1 INTPOGUCHION E 2 Introduction to Global Positioning System 2 1 How does GPS Work eee a ntt rere eed hose ope rU 6 2 2 GPS satellite Signals e ect En d obe uror 8 2 3 How accurate is OBS oae Eee ke cai nS 8 3 Introduction to Data Networking eeeeeeeeeeeeeeeeeee 3 1 Open Systems Interconnection OSI Reference Model
8. After the executable file is built it is then sent to the TINI The build program is called TINIConvertor and is supplied by Dallas Semiconductor The output file has a tini extension TiniConvertor can be run as follows C gt java TINIConvertor f Filename1 class f Filename2 class f Filename3 class o Filename tini d lt TINI Install Dir gt firmware tini db The usage of the TINIConverter command involves listing each class file after a f tag followed by a o and the name of the output file Finally the location of the tini db file which describes how files are converted is referenced with a d tag 4 2 DGPS and RTK using smartGPS SmartGPS provides data communication facilities to the GPS receivers It has ability to accept messages and transmit them to other machines Consequently it should have same ability for many GPS units to form a network However we would only use the two existing smartGPS units which allow us to do testing between one master GPS receiver and one rover receiver as seen in the figure 20 p A Real Time Kinematic GPS System Via the Internet Figure 4 3 Experimental scenario for a smartGPS Internet RTK DGPS network SATELLITE gt SIGNAL EY MASTER GPS RECEIVER ESS SSD Master IFA Roveri CHJ INTERNET UDP SATELLITE gt SIGNAL 3 ROVER GPS RECEIVER ESS gy 4 3 SmartGPS user interface SmartGPS is a very user friendly device th
9. AppleTalk only network environment 67 ees A Real Time Kinematic GPS System Via the Internet 13 Conclusion Based on the experimental results most TCP IP or UDP transmission with different packet size within a Local Area Network are also capable of providing throughput fast enough to accommodate Real Time Kinematic GPS applications Among these connections the best transmission path between the Master and Rover receiver is using the UDP protocol with 512 bytes packet size within a Local Area Network 10 100Mbps On average it only requires 1 2 micro sec to transfer a packet with 2 3 packet error rate It has also been demonstrated that the use of Cable modem 512kbps or 56kbps modem does not satisfies the RTK latency minimum requirement although some Cable modem connections are suitable for other GPS strategies such as DGPS The GPSApplet Controller provides a costless and advantageous way to control the Master or Rover receiver in any operating system Further development suggestions have been made so that the Real Time Kinematic can further reduce the packet travel time between GPS receivers 68 ees A Real Time Kinematic GPS System Via the Internet 14 References This thesis project is built upon the previous year s project smartGPS Written By Adrian Clark Antony Histon Peter von Konigsmark Electrical Engineering Undergraduate Project UNSW 2001 Australian Communications Authority Class Licensing
10. Extracted from the GPSCard log SPRTKA 154 266190 00 1 000 5 5 5 33 91776926442 151 23182328433 86 9908 0 0000 61 0 0128 0 0157 0 0369 0 0 4 52 1334321 4D PRTKA Structure SPRTKA week sec lag sv high L1L2 high lat undulation datum ID lat SdDev lon SdDev hgt SdDev rtk status posn type idle stn ID xx CR LF Field Field type Data Description SPRTKA lon hgt soln status Example PRTKA 872 2 hg Dinterential tag in seconds 5 f Number of matched sateliles may differ from the number in view fhigh Number of matched satellites above RTK mask angle observations from satellites LIL2 1 week 3 sec GPS time into the week in seconds lag 6 below mask are heavily de welghtod fhigh Number of matched satelites above RTK mask angle with both L1 and L2 available 7 8 lat Latitude of position in current datum in decimal fraction format A negative sign implies South latitude 9 Longitude of position in current datum in decimal fraction formal A negative sign Height of position in current datum in meters above mean sea level 174963 00 51 11358042429 114 04358006710 10594105 16 2617 fil 0 n 5 6 15 o Standard deviation of satution element in meters Solution status see Table D 1 Page 142 sn type xx lon 1 hgt 1 undulatio Geoidal separation in meters where ve is above ellipsoid and
11. Label Label RTK GPS Rover reciever location 2 add new add new add lati add long add heig add lati add long Label Label tudeData itudeData htData tudeSDData itudeSDData 79 A Real Time Kinematic GPS System Via the Internet add height SDData add new add new add new Label Label Label bButtonOne addActionListener this bButtonTwo addActionListener this bButtonThree addActionListener this bButtonFour addActionListener this bButtonFive addActionListener this bButtonSix addActionListener this b addActionListener this public void actionPerformed ActionEvent e if e getSource bButtonOne SimpleWrite sw new SimpleWrite Sw messageString fix position 33 91776927 115 2318233055 86 983 labelOne setText Submitted fix position 33 9 115 2 86 9 labelTwo setText labelThree setText labelFour setText labelFive setText labelSix setText labelSeven setText e g unlogall unfix etc latitudeData setText Latitude longitudeData setText Longitude heightData setText Height latitudeSDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard Deviation else if e getSource bButtonTwo SimpleWrite sw ne
12. STATUS AND TIME Commands Descriptions CLOCKADJUST Enable clock modelling amp 1PPS adjust DIFF_PROTOCOL 1 Differential protocol control EXTERNALCLOCK Sets default parameters of an optional external oscillator EXTERNALCLOCK Sets clock rate SETTIMESYNC Enable or disable time synchronization SUTCA Download UTC data 1 Intended for advanced users of GPS only es A Real Time Kinematic GPS System Via the Internet 75 Dn A Real Time Kinematic GPS System Via the Internet Command J z TM1A i T J Table 2 2 GPSCard Command Summary Description Syntax QTobows NowAlel ASCII log format loliows NovAtel ASCII jog format ober NovAtel ASCII log format lolows NowAlet ASCII log format oberes NowAiel ASCII log format lotows NovAtel ASCII log format QTolows NovAtel ASCII log format lobows NowAlel ASCI tog format eric retraction corrections li cfs latest co nutec patio oc and acceleration acts raw GPS en 1s njects RTCA format GPS comections in ASC Type 1 njacts RTCM format differential corrections in ASCII Type T injects receiver time ef 1 PPS acts UTC imormabon Power to the low noise amplifier of an active antenna on a pri to channel In assign a channel n assiqn al channels r i E CLOCKADJUST Disable cock mechanism COM T inkilize Serial Pon 1 9 2 COMn DTR Programmable DTR leaditail time mpm eium Sets maium age c
13. Short Range Spread Spectrum Devices 2001 online http www aca gov au publications info spreadsp htm Bertsekas D amp Gallager R Data Network Prentice Hall 2 Edition 1992 Chancogne D amp Austin M A short Java course 1996 online http www isr umd edu doc Java Course chap3 html Corvallis Mcirotechnology Inc Introduction to GPS 2002 online http www ctinc com gpsbook index htm Dick Smith Electronics Product Catalogue 2001 2002 online http www dse com au DHL Australia Tracking center May 2002 online http www dhl com au Goldman J Rawles P Applied Data Communications A Business Oriented Approach 3 Edition 2001 GPS GLONASS Data Center Germany 2002 online http igs ifag de index euref htm Gran D M An Introduction to Java 2001 online http www cs bsu edu bsjug intro html 69 ad A Real Time Kinematic GPS System Via the Internet Hada H Uehara K Sunahara H Murai J Petrovski l Torimoto H Kawaguchi S Differential and RTK corrections for the Internet car 1999 online http neo sfc wide ad jp watari WEB gnss99 pdf Hedling G Jonsson B Lilje C amp Lilje M SWEPOS The Swedish Network of Permanent GPS Reference Station June 2001 Huber J F Weiler D amp Brand H UMTS the Mobile Multimedia Vision for IMT 2000 A Focus on Standardization IEEE Communications Magazine September 2000 Kurose J amp Ross K Computer
14. ae mezsagss over reris 4 4 Flow Diagram of User Interface In order to show how user can control smartGPS with the buttons and system menu several screenshots are shown in appendices The first second and the third flow diagrams show available selections under Applications Diagnostics and Settings options respectively 22 eek A Real Time Kinematic GPS System Via the Internet 5 Introduction to Java Programming This introduction is meant to clarify the main issues of Java and to separate some of the myths and facts The purpose of this introduction is not to explain programming constructs but rather to clarify the purpose of the Java language Java was originally planned as a programming language for controller chips and various consumer electronics Given that a controller on a motor or some device may need upgrading in the future the idea was to write a language that would be very portable across different hardware In time the idea evolved into a language for desktop computers and in keeping with modern trends a language which interfaces to the Internet Gran An Introduction to Java 5 1 Object Oriented Language Java is an object oriented language The object oriented model focuses on the data and methods which manipulate the data Through the use of classes and other object oriented constructs the programmer models the behavior associated with data The object oriented approach to programming has the advantage o
15. longitudeData new Label heightData new Label latitude longitudeSDData new Label heightSDData new Label labelSeven new Label Latitude Longitude Height SDData new Label Standard Deviation Standard Deviation Standard Deviation e g unlogall unfix etc String message inputTex fileRead setLayou add new add new add new t new TextField message 15 Line 0 t new GridLayout 17 3 Label Label GPSCard APPLET CONTROLLER yy Label add new add new add new add bBut add bBut add bBut add labe add labe add labe add new add new add new Label Control master receiver Label Label tonOne tonTwo tonThree lone lTwo lThree Label Label Label r LO LO add new add new add new add bBut add bBut add bBut add labe add labe add labe add new add new add new add new Label Control rover receiver Label Label tonFour tonFive tonSix lFour lFive lSix Label Label Label add new add new add inpu add b add new add labe add new add new add new add new add new add new Label Manually enter command here Label Label tText Label lSeven Label Label Label Label
16. Avg 22 56 Rx Min 48 11 Max 55 84 Avg 54 32 UDP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 Tx Min 0 0 Max 91 M A Real Time Kinematic GPS System Via the Internet Data UDP 512 Bytes Unicast All Test Summary Tests Completed 10 Elapsed Time 00 00 22 TCP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Throughput in Mbits s Tx Min 1 62 Max 4 31 Avg 3 37 Rx Min 4 31 Max 4 73 Avg 4 53 Data UDP 256 Bytes Broadcast All Test Summary Tests Completed 10 Elapsed Time 00 00 22 TCP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Throughput in Mbits s Tx Min 0 83 Max 2 27 Avg 2 02 Rx Min 2 73 Max 2 94 Avg 2 84 Data UDP 256 Bytes Unicast All Test Summary Tests Completed 10 Elapsed Time 00 00 22 TCP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Throughput in Mbits s T3 AS Min 2 66 Max 2 81 Avg 2 84 Rx Min 2 94 Max 3 54 Avg 3 39 Data TCP 4 0 MByte All Test Summary Tests Completed 10 Elapsed Time 00 00 40 TCP Throughput in Mbits s Te Min 13 92 Max 24 04 Avg Rx Min 51 34 Max 54 83 Avg UDP Throughput in Mbits s TX Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Packet Error Rate Tx Min 0 0 Max Rx Min 0 0 M
17. Time Kinematics GPS system requirement Time out between Master receiver and around 0 02 seconds Rover receivers Physical distance between receivers 0 15 km does not apply on this project explained below Number of Satellites has to view in 4 or 5 sometimes common Time out between Master and Rover receivers If the time taken to send correction messages packet from the Master to Rover receiver is more than 0 02 seconds the Rover information would not get enough data to compute its exact location Therefore our aim is to make sure the Internet packet travel time is less than 0 02 seconds Types of connections to consider are 1 LAN to LAN within a network 2 Cable to modem and vice versa and 3 56kbps modem to 56kbps modem The other consideration is the transfer protocol of either TCP IP with respond and error checking or UDP without respond or error checking 42 aes A Real Time Kinematic GPS System Via the Internet Physical distance between receivers Since most people dealing with RTK GPS are using radio wave to transmit data from the master to the rover receiver there is a separation distance limit depending on the transmission range of the radio modem But this limitation does not apply to this thesis project because we are using Internet as a transfer media Number of Satellites has to view in common Although there is no radio wave limitation in this thesis project in
18. a response Figure 9 6 The snapshot usage of the PING command c Command Prompt A l C gt ping n 18 1 512 203 206 19 114 Pinging 203 206 19 from 283 from 283 from 283 from 203 from 283 from 283 from 283 from 283 from 283 from 283 266 266 206 266 266 206 206 206 206 206 114 with 512 bytes of data 19 19 a Be 19 19 19 19 19 19 19 114 114 114 114 114 114 114 114 114 114 bytes 512 bytes 512 bytes 512 bytes 512 bytes 512 bytes 512 bytes 512 bytes 512 bytes 512 bytes 512 Ping statistics for 203 266 19 114 Packets Sent Approximate round trip times in milli seconds Minimum C N am The additional options of the PING command that was used during testing were Usage Options Detailed test results are discussed in the section below ping 18 Received 180 Lost 169ms n count n count size target_name Maximum 282ms Number of echo request to send I size time 282ms time 27 ms time 278ms time 276ms time 264ms time 273ms time 212ms time 169ms time 178ms time 266ms Average Send buffer size TTL 117 TTL 117 TTL 117 TTL 117 TTL 117 TTL 11 TTL 11 TTL 11 TTL 11 TTL 11 loss 241ms target_name The targeted IP address 45 ud A Real Time Kinematic GPS System Via the Internet 9 6 Packet Travel Time Measurement The
19. and the Internet GPRS based data transfer using PDAs is among the promising techniques for Real Time access to both geo information GIS and geo referencing RTCM data using the same communication channels 34 Fee A Real Time Kinematic GPS System Via the Internet Figure 8 1 Reference stations in EUREF During the investigation on the protocols and other issues about Real Time GPS data streaming over Internet for instance latency accuracy system error rate etc few testing on this software was undertaken However because the list of EPN servers are only available in European countries true RTK GPS cannot be achieved as our rover RTK receiver was out of the maximum range from reference stations EUREF 2002 8 5 2 Differential and RTK Corrections for the Internet Car In Japan the common GPS correction services are depending on the radio broadcasting Internet actually is an alternative and excellent solutions for hunting high accuracy in GPS Internet offers many advantages over traditional radio link First the global Internetworking infrastructure offers high mobility and accessibility With sufficient resources such as software hardware technical support Internet can provide a low cost GPS service to people Differs from radio communications link radio broadcast licenses are no longer required Wherever Internet is available precise RTK GPS works as long as master and rover receivers are within certain acceptab
20. be smaller In general UDP packet header is small Disadvantage Smaller packet size means more packets have to be sent Since each packet has its own header therefore more Internet traffic is generated 39 Fee A Real Time Kinematic GPS System Via the Internet Large packet size e g 1460 Bytes Advantage Larger packet size can handle more data in each packet less packets means less header information has to be wasted Disadvantage Larger packet size would increase the probability of transmission errors which the data would not be resent But first of all we have to make sure the message traveling time and accuracy satisfy the Real Time Kinematic requirement in the Internet environment Figure 9 2 Possible location between GPS receivers SY i 3 km apart 2 i oy it J acme Andy s house Maroubra 25 km apart am Master receiver i ien Donald s house Parramatta In this chapter the Internet environment will be fully analysed via variety of experiments including the connection speed and the packet error rate with different types of Internet protocols Typical questions to consider are Connection speed Since the correction information required by the rover receiver is simple ASCII data would a 56kbps modem be capable of doing this 40 ad A Real Time Kinematic GPS System Via the Internet Type of connections It is important to minimise the traveling time of the correction message and it
21. cache memory therefore even modifications are made on the applet the browser usually can be updated promptly To overcome this problem the appletviewer which comes with the Java development kit can be used In the DOS command prompt change to the directory which contains the compiled GPSApplet version java and GPSApplet html files and type appletviewer GPSApplet html 10 6 Accuracy of the Computed Locations After the Rover receiver computed its location for example longitude 123 latitude 456 and height 789 it is hard to know how accurate these values are unless these values come with the standard deviation A good example of a computed Rover location using Real Time Kinematics is Figure 10 5 Comparison of the Actual and Rover receiver computed values located at EE Building UNSW Sydney Actual location Computed Values Standard deviation Latitude 33 91776927 33 91776529 0 011 Longitude 151 2318233055 151 23182334 0 015 Height 86 983 86 995 0 026 ees A Real Time Kinematic GPS System Via the Internet The above computed results are extremely accurate as the standard deviations are only around 2 cm 0 02 meter This is because the above value was taken when the master and rover were using the same antenna located at the rooftop of the EE building with the communication using 100Mbps within the University network If the communication link between the receivers is no
22. fraction format A negative sign plies West longitude Height of position in current datum in meters above mean sea level 114 04358003164 1059 4105 Geoidal separation in meters where positive is above elipsoid and negative is 16 2617 below ellipsoid Current datum see Appendix G Page 234 Standard deviation of latitude solution element in meters Lae tgo 15 soln status a RIK status see Tables D 3 D 4 Page 143 posn type Position type see Table D 2 Page 143 Dyna Standard deviation of longtude solution element in meters Standard deviation of height solution element in meters Solution Status see Tawe D 1 Page 142 Reference station identification RTCM 0 1023 or RTCA 266305 15179385 ICRILF 90 fe M A Real Time Kinematic GPS System Via the Internet Appendix D Selected Experimental Results University Local Area Network UDP and TCP IP Test Results From UNSW Residential college 129 94 199 101 100Mbps To UNSW T E Blue Tooth lab 149 171 37 185 100Mbps Date Monday 16th Tuesday 17th and Saturday 21st September 2002 Data UDP 1460 Bytes Broadcast All Test Summary Tests Completed 10 Elapsed Time 00 00 24 TCP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Throughput in Mbits s Xx Min 3 00 Max 5 82 Avg 5 39 Rx
23. rover location would not be accurate In the experiment performed except for some Local Area Network UDP connections all other UDP based connections failed this requirement From the experimental result it suggested that if the connection involved traffic outside a local area network for example involving other network or modem users then the transfer of packet correction information between receivers would not be fast enough to satisfy the Real Time Kinematic requirement 49 A Real Time Kinematic GPS System Via the Internet Hence only LAN connections can satisfy the RTK GPS requirements From To Type of Packet size Travel time Error speed speed connection bytes micro sec rate 100MbpsLAN 100MbpsLAN UDP 256 bytes 0 7 0 11 100MbpsLAN 100MbpsLAN UDP 512 bytes 1 1 2 6796 100MbpsLAN 100MbpsLAN UDP 1460 bytes 2 0 6 1196 100MbpsLAN 100MbpsLAN TCP IP 256 bytes 1 1 096 100MbpsLAN 100MbpsLAN TCP IP 512 bytes 1 5 096 100MbpsLAN 100MbpsLAN TCP IP 1460 bytes 2 6 096 From these six connections in order to select the best connection a decision has to be made on whether TCP IP or UDP is to be used For Real Time Kinematic it is best to use UDP since the packet travel time is relatively less than the TCP IP Although there would be error packet generated when using UDP it will not affect the accuracy of the computed position if the error rate is relat
24. single user to afford 8 4 Network RTK A set of reference station network is a way of increasing the range of the RTK corrections Since the atmospheric errors are distance dependent the single station RTK corrections may not work if distance from master to rover stations is more than 10 km If Internet is combined with the use of RTK network RTK service can provide high accuracy and large area coverage S Wahlund 2002 33 tenet A Real Time Kinematic GPS System Via the Internet 8 5 Different Approach on DGPS and RTK 8 5 1 EUREF EUREF European Reference Frame is a Sub Commission of IAG s International Association of Geodesy Commission X on Global and Regional Geodetic Networks In order to disseminate RTCM corrections using Internet Protocol in Real Time for precise differential positioning and navigation purposes EUREF sets up and maintains a differential GNSS infrastructure DGNSS on the Internet using stations of its European Permanent Network EPN The free client software called Euref ip rtcm Windows 98 00 XP ftp igs ifag de software euref ip rtcm zip is available for users who want to access data streaming over Internet and connected GSM GPRS cellular phone network for GPS positioning and other navigator applications This software aims to meet the growing need for Europe wide improved Real Time determination of coordinates It makes use of recent developments in the interconnection of mobile communication
25. the use of sequenced acknowledgment with retransmission of packets while UDP provides a simple message delivery for transaction oriented services TCP IP is very reliable but it may not suitable for high precision Real Time applications such as Real Time Kinematic RTK positioning since it requires an acknowledgement to confirm the data arrival On the other hand UDP is able to provide faster data transmission although the reliability is not as high as TCP with a possibility of data losses Since fast differential data transmission is essential for the success of a Real Time positioning system to derive accurate positions UDP protocol is preferred when dealing with the Internet based RTK DGPS system 31 eet A Real Time Kinematic GPS System Via the Internet 8 Real Time Kinematic RTK means the position is obtained in real time Master station with known position while a moving rover station at unknown point Usually RTK is considered when DGPS is being used At least four or more satellites need to lock the position of receiver continuously in order to achieve RTK The corrections will increase the accuracy if both master and rover stations have atmospheric biases 8 1 Principle The receiver should be capable of a one second update rate The location of the reference station will be the same as for a code phase tracking DGPS system The processor used in the reference station will compute the pseudo range and carrier phas
26. 1460 Bytes Unicast Ld Data UDP 256 Bytes Broadcast d Data UDP 256 Bytes Unicast Da Data UDP 512 Bytes Broadcast 4 Data UDP 512 Bytes Unicast Tl 3 Nodes I1 19 Packages Tests Completed 500 Elapsed Time 00 28 42 TCP Throughput in Mbits s Min 0 00 Max 0 00 Avg 0 00 Min 0 00 Max 0 00 Avg 0 00 UDP Throughput in Mbits s Tx Min 0 46 Max 2 04 Avg 1 75 x gt Tesi BIET Tie A Progress as E TCP mi UM VATER ABMS Mower Mir TM TIT Pv 15 1 0 05 00 All Data T T inei e MP Elapsed Time 00 28 42 192 168 1 102 gt 192 168 1100 Testing Finished This program can be used to create real world application traffic hence the network performance can be tested It can generate TCP IP or UDP traffic using different packet sizes 256 512 or 1460 Bytes To use this program a folder within the program has to be shared publicly with the ability of full access control therefore two computers can communicate and perform testing 44 A Real Time Kinematic GPS System Via the Internet The Windows build in DOS command ping was also used in our experiments The PING command sends a test packet data to a designated IP address If the data packet arrives it will send a response and the approximate round trip times in milli seconds could then be calculated But this command only works with TCP IP because UDP would not provide
27. E Mamusiky enter command here Submt Command 9 acceptipot mode HTK GPE Rover reciever localion em Lande Lorgitade Height Standyrd Deviation Btancdsrd Deviaton Starcterd Deviaton zi E Apeiat Apina iara gt 7 gu To use this applet it is assumed that the computer s serial port COM is connected to the receiver s COM1 port and that a remote terminal is connected to the receiver s COM2 port Also this computer is required to connect to the Internet or a local area network 54 ees A Real Time Kinematic GPS System Via the Internet 10 4 Communicate with the Receiver Communication with the receiver consists of issuing commands through the COM1 or COM2 port from an external serial communications device The communication between the GPS receiver and a computer is achieved by virtue of the GPS firmware that resides within the GPS receiver For communication to occur both the receiver and operator interface have to be configured properly The receiver s default port settings are as follows RS232C 9600 bps no parity 8 data bits 1 stop bit no handshaking echo off Changing the default settings requires using the COMn command which is described in the MiLLennium Command Descriptions Manual Although the receiver can operate at bit rates as low as 300bps this may not always be desirable For example if several data logs are active i e a significant amount of information needs to be trans
28. INI board and the method of handling GPS receiver data that would further enhance the attractiveness of the project Figure 12 1 A Real Time Kinematic GPS system via the Internet i MASTER REFERENCE STATION MOVING ROVER STATION ONE MOVING ROVER STATION TWO 12 1 Additional Serial ports and Address space The address space of the TINI is designed in such a way that the user has complete control and freedom to add extra devices Hence logic to provide additional I O can be added in order to interface additional serial ports and other devices 64 ees A Real Time Kinematic GPS System Via the Internet When broken down serial ports consist of a two wire asynchronous serial interface One line is needed for transmitting the other for receiving Other common serial port handshaking lines such as CTS and RTS could also be added but most GPS receivers do not require them for use SmartGPS 2001 Any number of serial ports could be added to a smartGPS unit with only minimal hardware and software routines These software routines would have to be written in native assembler code as Java would not be fast enough for this asynchronous communication 12 2 Host Internet Server A web server can be hosted at the University domain with the applet controller hence the system can be used in areas around the University Also people around the world can monitor the rover receiver position as long as they have Internet ac
29. Min 5 87 Max 6 82 Avg 6 55 Tx Min 0 00 Max 0 00 Avg 0 00 Data UDP 1460 Bytes Unicast All Test Summary Tests Completed 10 Elapsed Time 00 00 24 CP Throughput in Tx Min 0 00 Rx Min 0 00 UDP Throughput in Mbits s Tx Min 1 30 Max 6 87 Avg 5 83 Rx Min 6 84 Max 7 45 Avg 7 25 UDP Packet Error Rate Tx Min 0 05 Max 32 1 Avg 6 10 Rx Min 0 00 Max 4 00 Avg 0 40 Data UDP 512 Bytes Broadcast All Test Summary Tests Completed 10 Elapsed Time 00 00 22 TCP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Throughput in Mbits s Tx Min 0 73 Max 3 39 Avg 3 01 Rx Min 3 78 Max 4 06 Avg 3 98 Data TCP 1 0 MByte All Test Summary Tests Completed 10 Elapsed Time 00 00 39 TCP Throughput in Mbits s Tx Min 8 58 Max 22 71 Avg 18 52 Rx Min 0 65 Max 52 77 Avg 46 20 UDP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 UDP Packet Error Rate Tx Min 0 0 Max Data TCP 2 0 MByte All Test Summary Tests Completed 10 Elapsed Time 00 00 29 TCP Throughput in Mbits s TeS Min 11 81 Max 23 97 Avg 21 56 Rx Min 46 96 Max 55 42 Avg 53 84 UDP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 UDP Packet Error Rate Tx Min 0 0 Max O 0 All Test Summary Tests Completed 10 Elapsed Time 00 00 34 TCP Throughput in Mbits s Tx Min 13 59 Max 24 56
30. Networking A Top Down Approach Featuring the Internet Addition Wesley 1st Ed 2001 Lachapelle R amp Fattouche M Cellular Telephone Positioning Using GPS Time Synchronization GPS World April 1998 Loomis D The TINI Specification and Developer s Guide New York Addison Wesley 2001 McElroy S Robins l Jones G amp Kinyside D Exploring GPS A GPS users guide 2nd Edition 2001 MiLLennium GPSCard and Enclosures Guide to Installation and Operation 2001 online http www novatel ca Muellerschoen R J Bertiger W l amp Lough M F Results of an Internet Based Dual Frequency Global Differential GPS System Procedings of IAIN World Congress San Diego CA June 2000 National Air and Space Museum How does GPS works May 2002 online http www nasm si edu galleries gos work html 70 ad A Real Time Kinematic GPS System Via the Internet Network Based Techniques for RTK Applications 2001 online http www ion org meetings past gos2001 d1 html Real Time Kinematic differential GPS surveys 2001 online http www nap usace army mil channel em 16 pdf SNAP Australia 2002 online http www gmat unsw edu au snap Shields S Flinn J amp Obregon A GPS in Pits Differential GPS Applications at Moreni Copper Mines GPS World 2000 Tanenbaum A S Computer Networks Prentice Hall 3 Ed 1996 Thai B Undergraduate Course TELE3018 Data Network 1 online http alpha400
31. OL Differential Protocol Control FREQUENCY_OUT Variable frequency output programmable LOG Logging control RINEX Configure the user defined fields in the file header RTCMRULE Sets up RTCM bit rule RTCMI6T Enters an ASCII message SEND Sends ASCII message to COM port SENDHEX Sends non printable characters 1 Add an offset to the L1 pseudorange to compensate for SETLIOFFSET signal dikaya 1 Intended for advanced users of GPS only GENERAL RECEIVER CONTROL AND STATUS Commands Descriptions SALMA CRESET Reset receiver to factory default DYNAMICS Set correlator tracking bandwidth HELP On line command help RESET Performs a hardware reset OEM only Saves the latest almanac in NVM VERSION Software hardware information 73 A Real Time Kinematic GPS System Via the Internet POSITION PARAMETERS AND SOLUTION FILTERING CONTROL Commands Descriptions CSMOOTH Sets amount of carrier smoothing DATUM Choose a DATUM name type ECUTOFF Satellite elevation cut off for solutions FIX HEIGHT Constrains to fixed height 2D mode FIX POSITION Constrains to fixed lat lon height FRESET Clears all data which is stored in NVM SIONA Download ionospheric correction data IONOMODEL vini correction to use MiLLennium with the LOCKOUT Deweights a satellite in solutions SPVAA Position velocity and acceleration in ECEF coordinates RTKMODE Setup the RTK mode UNDULATION Ellipsoid geoid separation USERDA
32. Select the correct Baud rate 4800 9600 or 19200 Logging GPS Data to either Memory card or Remote PC Control the brightness of the LCD screen Although this is a very user friendly design it can only select the three commands out of sixty two possible commands listed in the appendix which are already programmed in the TINI board Hence many advance instructions for the receivers can not be used 53 Fe A Real Time Kinematic GPS System Via the Internet 10 3 GPS Applet Controller To overcome the above problems a Java applet called GPSApplet version java is built It can be opened using the file GPSApplet html these files are attached in Appendix C and the CD This Java applet can be uploaded to a homepage Hence as long as there is a computer which supports Java and has Internet connection it can be used to control the master and rover receivers Figure 10 3 GPS Applet Control Panel rae nemak GPS System Wia the Intenet Micresolt piternet Enplorcr Fe Edt Ven Favorites Tod Hep FJ bal E Nl te B qe OD Z7 09 Item Jue OS Bs oS Aides hutp J oeodciss cc joge rheds z Morton Antares E Ld GPS Applet Control Panel DE GFSCarnd APPLET CONTROLLER porco noi mas F lg ir mmm GEE Fix M ztor Raraiwar loc alion Logging Naster receiver data Sel DOPE timaaut j Appel s Como mer ratatet i Recewe Doth from Master Lo9gry Rover reramar dalla Damay Rover Localion Ew BOOT
33. TUM User customized datum WAASCORRECTION Controls handling of WAAS corrections 1 Intended for advanced users of GPS only Commands ASSIGN CONFIG DYNAMICS SATELLITE TRACKING AND CHANNEL CONTROL Descriptions Download almanac data file Satellite channel assignment Switches the channel configuration of the GPSCard Sets correlator tracking bandwidth FIX VELOCITY RESETHEALTH Aids high velocity reacquisition Reset PRN health SETHEALTH Commands Overrides broadcast satellite health WAYPOINT NAVIGATION Descriptions MAGVAR Magnetic variation correction SETNAV Waypoint input 74 DIFFERENTIAL REFERENCE STATION Commands Descriptions DGPSTIMEOUT Sets ephemeris delay FIX POSITION Constrain to fixed reference LOG Selects required differential output log POSAVE Implements position averaging for reference station RTCMRULE Selects RTCM bit rule SETDGPSID Set reference station ID DIFFERENTIAL REMOTE STATION Commands Descriptions ACCEPT Accepts RTCM1 RTCA or RTCAB differential inputs SALMA Input almanac data DGPSTIMEOUT Set maximum age of differential data accepted Performs a hardware reset RTCA differential correction input ASCII RTCM differential correction input ASCII RTCMRULE Selects RTCM bit rule SETDGPSID Select differential reference station ID to receive CLOCK INFORMATION
34. UnsupportedCommOpera readThread new Thread this readThread start public void run tty ca public void seriall swit case case case case case case case case case case Thread sleep 20000 tch Interrupted Exce ption e Event SerialPortEvent event ch event getEventType SerialPortEvent BI SerialPortEvent OE SerialPortEvent FE SerialPortEvent PE SerialPortEvent CD SerialPortEvent CTS SerialPortEvent DSR SerialPortEvent RI SerialPortEvent OUTPUT BUFFER EMPTY break SerialPortEvent DATA AVAILABLE byte readBuffer new byte 20 try while inputStream available 0 int numBytes inputStream read readBuffer System out print new String readBuffer catch IOException e break tionl Exception e 86 fe A Real Time Kinematic GPS System Via the Internet M File name Purpose SimpleWrite java To write command to the Serial Port import java io import java util import javax comm public class SimpleWrite Static Enumeration portList Static CommPortIdentifier portId static String messageString Hello world n static SerialPort serialPort static OutputStream outputStream public static void main String args portList CommPortIdentifier getPortIdentifiers while portList hasMoreElements portId CommPor
35. at comes along with a LCD buttons and a set of simple operations The LCD display offers a variety of commands that are useful in programming the screen output It provides intelligence to enable easily adaptable features such as graphical capabilities The class file TLCD java is loaded in smartGPS for user to communicate with LCD display Three input buttons and a fourth reset button have been interfaced on the smartGPS allowing user to select different options for smartGPS operations They are Up Down Enter and Reset button 21 ees A Real Time Kinematic GPS System Via the Internet Java software was required to ensure that the buttons worked in conjunction with the screen to display status information and execute programs Moreover the smartGPS is designed to begin run its software when the power supply is switched on In order to give feedback to the user there are several displays that are shown on the LCD screen These screens are stored as String objects in the Screens java class Then they are displayed on the screen using the TLCD java class Figure 4 4 has shown the detail interaction of smartGPS class files These files are crucial in making smartGPS user friendly Figure 4 4 The main smartGPS program smartGPS java Seraens java flarar zetras slet using tan slerez ST scree cs DataLog java TLCD Java TUDPServ ava Clear brad rs aqqing Hass al has av ers n Tass dra aaa iiU Zenmurka e v LTD ds
36. atic GPS System Via the Internet 8 5 4 SWEPOS Figure 8 3 Infrastructure of SWEPOS SWEPOS is a network of permanent GPS reference stations in Sweden It provides service about positioning in real time with meter level accuracy and by post processing with centimeter level accuracy since 1998 One of the main purposes of SWEPO is providing DGPS and RTK data in RTCM format to real distributors Currently all the SWEPOS stations have real time connections to the control center in Gavle through leased lines of which TCP IP protocol is being used Raw data and RTCM messages are transferred to control center They are used for post processing which can be fetched from control center through WWW FTP server Then distributors of real time DGPS and RTK can receive SWEPOS real time corrections from the main control center via network of server and Internet with meter level accuracy G Hedling B Jonsson C Lilje and M Lilje 2001 37 f A Real Time Kinematic GPS System Via the Internet 9 Communicate between GPS receivers 9 1 Use of Radio modem Real Time Kinematic RTK is a high precision GPS based positioning technique that requires raw carrier phase data correction information to be transmitted from a base GPS station to the mobile GPS receiver via a data link with very low latency In order to calculate the exact position of the rover receiver the master receiver has to continuously sending correction information to the rov
37. ation time to receivers can be greatly reduced The removed data will be added back into the instruction stream at the receiver before passing it onto the hardware The process of adding data would take much less time than actually transmitting them At the moment the packet size is 512 bytes therefore around 4 lines 123 characters each of data can be fitted in each packet But if each line is reduced to 73 characters then each packet can fill at least 7 lines of data 66 ees A Real Time Kinematic GPS System Via the Internet 12 6 AppleTalk According to the experiment performed the local area network is the best transmission path between GPS receivers In fact beside TCP IP and UDP Apple Mac computers also support AppleTalk as a data transfer protocol AppleTalk Update Based Routing Protocol AURP is a tunneling and a routing protocol AURP provides the feature of AppleTalk tunneling in TCP IP This feature enables two isolated AppleTalk networks to be connected by way of a TCP IP network AURP provides update based routing and reliable delivery of routing information To reduce the amount of bandwidth update based routing sends updates to peer routers only when network routing information changes rather than sending periodic broadcasts of the routing table Therefore having an AppleTalk implementation in our program instead of creating TCP IP packets manually could be an easier way to get the program running an
38. ax Data TCP 5 0 MByte All Test Summary Tests Completed 10 00 00 48 TCP Throughput in Mbits s Tx Min 7 97 Max 23 37 Avg 21 38 Rx Min 53 44 Max 55 16 Avg 54 24 UDP Throughput in Mbits s Tx Min 0 00 Max 0 00 Avg 0 00 Rx Min 0 00 Max 0 00 Avg 0 00 92 FE A Real Time Kinematic GPS System Via the Internet Appendix E Operate smartGPS TINI board Send or log data Boot up screen hides after 4 sec Select 1 and then Enter Choose 1 and Enter L S Choose either 2 or 3 and Enter Choose baud rate and Enter baud and Enter Screen indicating data being logged Choose address to send to and then Enter Screen indicating logging amp sending Screen indicating sending only 93 p A Real Time Kinematic GPS System Via the Internet Control the brightness of the LCD screen Boot up screen hides after 4 sec Choose 3 and Enter Choose 1 and Enter Choose 2 and Enter Choose 3 and Enter to Return to previous screen 94 p A Real Time Kinematic GPS System Via the Internet General Setting of the smartGPS TINI Boot up screen hides after 4 sec Choose 2 and Enter Choose 1 and Enter Choose 2 and Enter If Choose 3 and Enter Return to previous screen 95
39. ce and destination and restricting the size of datagrams depending on the network specifications J Kurose and K Ross 2001 Transmission Control Protocol TCP TCP is connection oriented protocol meaning that TCP will set up maintain and tear down a connection TCP keeps track of the status and state of data passing through it It provides reliable end to end data transmission with several mechanisms like flow control congestion control error recovery and so on TCP can also multiplex data from different applications and is full duplex User Datagram Protocol UDP UDP also resides in the Host to host layer with TCP UDP is connectionless and is merely a transport level protocol for the applications in the layer above Connectionless means that the datagram is sent without first setting up a connection UDP does not do any end to end error checking but uses a checksum in the UDP header This checks only the correctness of the header UDP is used for small data transfer where an error is not a serious problem for instance RTK applications It is faster and cheaper than TCP because it doesn t have the expensive error checking software nor does it have to take the extra time to error check ad A Real Time Kinematic GPS System Via the Internet 4 Introduction to smartGPS SmartGPS is used as an interface between RTK GPS receiver and Internet throughout the entire thesis project smartGPS was from last year 4 year t
40. ceiver does not have to transmit anything to the satellite and the satellite does not know the receiver is there Hence there is no limit to the number of GPS receivers that can be using the system at any one time 2 3 How accurate is GPS In early 1990 the US Department of Defence introduces a policy of degrading the civilian use of the GPS technology called Selective Availability Basically they decided to scramble the satellite signals so that civilians could not get accurate GPS results As GPS becomes widely used in safety scientific and commercial aspects pressure from world wide made the White House terminated this policy from May 2000 Nowadays most hand held GPS receivers have about 10 meters of true horizontal and about 20 meters true vertical accuracy Other types of receivers use a method called Differential GPS DGPS to obtain much higher accuracy of up to 1 meter which will be explained in later chapters Eanes A Real Time Kinematic GPS System Via the Internet 2 4 Errors in GPS The following sources of error could affect the accuracy of the GPS positioning results so that system reliability will be reduced Atmosphere When the satellite GPS signal got refracted when it travels through ionosphere and troposphere of the earth Therefore errors will occur in expected signal travel time and distance between satellite and receiver Temperature humidity and pressure are key factors affecting atmospheric error Fo
41. cess 12 3 Display Features The TINI LCD display interface can be easily updated or altered This will allow for additional smartGPS features in further development smartGPS 2001 12 4 Further Experimentation Experiments with further GPS technology for example carrier phase tracking methods would be advisable in order to make the Real Time Kinematic System a more accurate package 65 e A Real Time Kinematic GPS System Via the Internet 12 5 Remove Unnecessary Data before Transmitting To increase the efficiency of the computed rover receiver results the packet travel time from master to rover receiver has to be as least as possible At the moment the master receiver is sending a large amount of duplicated data Structure PRIKA week sec lag sv high L1L2 high lat lon hgt undulation datum ID lat SdDev lon SdDev hgt SdDev soln status rtk status posn type idle stn ID xx CR LF 1 PRTKA 154 266210 00 1 000 6 5 5 33 91776928615 151 23182333583 86 9865 0 0000 61 0 0128 0 0157 0 0369 0 0 4 54 1334321 47 PRTKA 154 26621 1 00 1 000 6 5 5 33 91776926423 151 23182332702 86 9862 0 0000 61 0 0128 0 0157 0 0369 0 0 4 50 1334321 46 The text in red is the duplicated data Out of the 123 characters in each line 51 characters are redundant and occupy 4196 of bandwidth If only relevant data is sent only 73 of the 123 characters are required hence the packet propag
42. cheme Java File called file java source Java compiler File called file class Java bytecode Java Virtual Machine Interpreter Hardware One advantage of this approach is that the Virtual Machine has already been ported to different type of hardware So any Java program that was written can run on any of those Virtual Machines without any changes Otherwise someone has to develop a new Virtual Machine for the specific hardware 5 4 High Performance Java is a high performance language Most interpreted languages are roughly twenty times slower than an equivalent compiled program written in C Java is no exception to this rule but with the advent of new technologies such as Just In Time JIT compilers and upcoming Java accelerator chips the gap narrows For calculation intense applications it is best to supplement Java with a compiled language but this will not be the case in the future 25 Fe A Real Time Kinematic GPS System Via the Internet 6 Possible Applications 6 1 Courier Shipment Tracking Service As the world become more globalise government agencies companies and individuals increasingly rely on courier services In the market there are several courier companies offering similar services In order to compete with each other they have to offer fast responsive and cost effective deliveries to satisfy customers need One of the most important services customers looking for is the s
43. d to DGPS The basic idea behind DGPS is that two or more receivers observing the same satellites will take similar measurements with similar errors if they are close to one another By placing a receiver said to be a reference receiver at a known position it is possible to evaluate the theoretically correct measurement values according to the known position and then to compare these theoretical values with the actual ones taken The difference between both values gives the measurement error which can be used to provide corrections to receivers mobiles that are placed at unknown positions Figure 7 1 Scenario of DGPS GPS SATELLITE i p A PSEUDO RANGE CORRECTIONS GPS amp 9 DATA LINK Ww DATA LINK CORRECTIONS PROCESSOR MOBILE STATI 1 REFERENCE STATION 29 aes A Real Time Kinematic GPS System Via the Internet For Real Time applications a continuous data link must be established between the reference network and the rover stations in order for the DGPS users to receive the differential corrections generated from the reference network smartGPS 2001 Local and regional area differential positioning radios and local communication systems are usually used while for wide area differential positioning satellite communication is appropriate although it is much more expensive to use As the Internet become more and more popular it could become a cost effective and efficient alternative
44. does not really matter if there is a small amount errors for Real Time Kinematic system would UDP be a better choice compare to TCP IP Distance between GPS receivers Internet can be connected in most parts of the world would that mean can place my rover receiver anywhere as long as there is Internet connection and a clear sky is above me to receive satellite information 9 3 UDP Packet Travel Time As soon as packet arrives to the designated port the algorithm of emulating packet switching calculates the departure time from the emulating specified link speed delay and a size of the packet Creating packet switching condition for UDP packets 2002 online The interval time is nothing secret For example if the link speed is 500kbps then Speed bits sec 8 500 000 8 byte microsec 1 000 000 1 000 000 0 0625 byte microsec 62 5 kilo byte per second kbps Consider if the packet size is 512 bytes and we would like to calculate the interval time taken for each packet We can times the packet size with a reciprocal of the calculated number above 1 000 000 x bytes bytes 1 000 000 x 512 microsec Speed bits sec 8 500 000 8 8 192 microsec 41 ees A Real Time Kinematic GPS System Via the Internet 0 0082 second around 0 01 second taken for each packet 9 4 Real Time Kinematics GPS system requirement As mentioned in the chapter 7 typical RTK GPS requirements are Figure 8 4 Summary of Real
45. e corrections and format the data for the communications link S Wahlund 2002 Traditionally both DGPS and RTK are achieved by using radio communications link which transmits GPS correction message from master receiver to another mobile receiver However limitations of using radio are important issues when using RTK 32 aes A Real Time Kinematic GPS System Via the Internet Fortunately Internet seems to be a good solution to replace the radio in achieving RTK Centmetric accuracy can be achieved if carrier measurement is transmitting in real time and distance from master to rover station less than 20 kilometers Possible applications of RTK such as surveying on water supply and sewer systems car navigation and so on are benefits to our lives True RTK can be achieved by using temporary or permanent master stations 8 2 Temporary Master Station A standard dual frequency receiver and a radio modem are required when using temporary master station However even this method can keep RTK at low cost drawbacks such as radio range limit additional task of setting up reference station cannot be ignored 8 3 Permanent Master Station When using this method master station placing on top of the building can operate RTK 24 hours a day It is equipped with an external radio antenna so that it provides large coverage area Unfortunately unless multiple users can share the cost otherwise high cost of this manner is very hard for a
46. ed in this project belongs to a package called MiLLennium GPSCard which was manufactured by NovAtel Inc located in Canada The package comes along with a software called GPSolution which is a Microsoft Windows based graphical user interface that allow users to access the receivers features Figure 10 1 A graphical user interface GPSolution for the GPSCard t ba y aas Puk LE AFFELE 1P L Ree tee a Sottec 8 wecck Serifat j LIT xL sohenBies SZENE m i Ge t 2 LAT S 33917768210 0 016m Std Dev LON E 151231823250 0 016m Std Dev HGT 86 992m MSL 0 028m Std Dev Fri Nov 01 2002 01 58 38 PM UTC Type RT2 Narrow of Sats 7 6 6 Dif Lag tsec Idle 51 Ref iD 0 Ter elg piset FI I fe 22009880 Wo mgeadsles ect But if the user is not using Microsoft Windows such as Linux or have not got this program installed in the computer then he or she would not be able to control the Master or Rover receivers 52 f A Real Time Kinematic GPS System Via the Internet 10 2 TINI LCD Screen Last year the smartGPS group created a LCD screen with input buttons attached to the TINI board This LCD screen can display up to 80 characters in 4 lines while the three input buttons can perform selections like up down and enter in the smartGPS menu Figure 10 2 smartGPS TINI LCD screen with input buttons The three programmed commands included
47. ee unsw edu au tele3018 Thales Company Technologies Differential GPS May 2002 online http pro thalesnavigation com us pro scripts techno_gps techno_gps_dgps asp TINI ibutton com May 2002 online http www ibutton com TINI Tsukamoto A Creating packet switching condition for UDP packets 2002 online http www columbia edu at541 src emulator html Algorithm Trimble Navigation Limited 2002 online http www trimble com gps Tyson J How OSI works 2001 online http www howstuffworks com osi htm 71 ees A Real Time Kinematic GPS System Via the Internet Wahlund S Production measurements with Network RTK Tests and analysis 2002 Weber G Real Time Streaming of DGPS Corrections over Internet June 2002 Wilson G OSI layer model 2001 online http www geocities com SiliconValley Monitor 3131 ne osimodel html Wormley S J Sam Womley s DGPS 2002 online http www edu observatory org gps dgps htm Yang C amp Kim S The current status of GPs network datum transformation and real time kinematic GPS positioning in Korea 2001 72 f A Real Time Kinematic GPS System Via the Internet 15 Appendix Appendix A Standard Command Tables Table 2 1 Commands By Function Table COMMUNICATIONS CONTROL AND STATUS Commands Descriptions COMn COMn port configuration control COMn_DTR DTR handshaking control COMn_RTS RTS handshaking control DIFF_PROTOC
48. ents portId CommPortIdentifier portList nextElement if portId getPortType CommPortIdentifier PORT_SERIAL if portId getName equals COM1 if portId getName equals dev term a SimpleRead reader new SimpleRead public SimpleRead try public synchronized CommPort open String appname int timeout throws PortInUseException Opens the communications port open obtains exclusive ownership of the port If the port is owned by some other application a PORT OWNERSHIP REQUESTED event is propagated using the CommPortOwnershipListener event mechanism If the application that owns the port calls close during the event processing then this open will succeed There is one InputStream and one OutputStream associated with each port After a port is opened with open then all calls to getInputStream will return the same stream object until close is called serialPort SerialPort portId open GPSApplet 2000 catch PortInUseException e try inputStream serialPort getInputStream catch IOException e try serialPort addEventListener this catch TooManyListenersException e serialPort notifyOnDataAvailable true try 85 A Real Time Kinematic GPS System Via the Internet ca serialPort setSerialPortParams 9600 SerialPort DATABITS_8 SerialPort STOPBITS_1 SerialPort PARITY_NONE tch
49. er Receive Data from Master Logging Rover receiver data Rover Receiver location is listed below Manually enter command here Submit Command e g unlogall unfix etc RTK GPS Rover reciever location Latitude 33 91776926442 Longitude 151 23182328433 Height 86 9908 Standard Deviation 0 0128 Standard Deviation 0 0157 Standard Deviation 0 0369 Applet Pgh 10 4 7 Manually enter command Besides the six most frequent used commands above there are a total of sixty two possible commands which can be used by the receiver To use these commands users can simply enter the command in the textbox provided in the applet A confirm message will be displayed once the command has been submitted The next three frequently used commands are unlog unfix and fix height For a listed of the full sixty two commands please refer to the appendix Manually enter command here FIX HEIGHT 4 567 66 CR LF Crew eme Submitted FIX HEIGHT 4 567 66 CRI LF RTK GPS Rover reciever location Latitude Longitude Height Standard Deviation Standard Deviation Standard Deviation Applet 28h 59 ud A Real Time Kinematic GPS System Via the Internet 10 5 Editing the GPSApplet Controller Modification on the java applet can be made on file GPSApplet version java Applet can be opened by running the file GPSApplet html using a browser But since the browser has
50. er receiver Hence the traveling time of this correction information between receivers has to be very short Otherwise there will be a time out error problem and the Rover receiver position can not be calculated Figure 9 1 Communication between GPS receivers via radio wave WAVE UNA mW 7 SATELLITE See MASTER ROVER GPS RECEIVER GPS RECEIVER ANTENNA RADIO RADIO MODEM MODEM Nowadays the most common way to send this information is using radio modems RTCM Radio Technical Commission Maritime is an internationally accepted format for expressing Real Time DGPS corrections 38 f A Real Time Kinematic GPS System Via the Internet 9 2 Converting UDP Packet In order to send the correction message from the master receiver to the rover receiver using the Internet these data has to convert to packets first In this thesis project the conversion of the data to packets is handled by the smartGPS TINI board The size of the packet can be modified by changing the DataLog java file the default packet size is 512 Bytes Figure 9 3 Connection between GPS receivers using TINI boards TINI BOARD TINI BOARD If sending data using UDP User Datagram Protocol in order to choose the best packet size the following factors have to be taken into consideration Small packet size e g 256 Bytes Advantage Smaller packet size means the probability of there is an error in transmission would
51. essary Data before Transmitting 66 12 67 AppleTalk asses oo ortos ee ree tinte Eo Epor v pep dae de dto eda shop onte hr 67 SEE eS ELICIT ME 68 T4 Referente m 69 15 Appendix A Standard Command Tables 73 B Developed Software sssssss s 78 C Logs Summary sss oe sotac oc ace pea a Rosae ten dee ode 89 D Selected Experimental Results 91 E Operate smartGPS TINI board 93 fee A Real Time Kinematic GPS System Via the Internet 1 Introduction The aim of this thesis project is to develop a Real Time Kinematic GPS system based on the Internet connection so accurate rover GPS receiver positions can be found To achieve that the data has to be transferred in real time to avoid the GPS receiver time out problem Managing the traffic delay over the Internet would be the biggest challenge of this project In other words the key of this project is to minimise the packet travel time from the GPS master receiver to rover receivers Intensive investigation is performed on Internet based protocols TCP IP and UDP in order to find the best transmission path which satisfies the Real Time Kinematic requirements A homepage with Java applet control panel is created to enable users issuing commands to master or rover receivers as well as monitoring the location of rover receivers in real time A Real Time Kinematic GPS system via the Interne
52. eviation e getSource heightSDValue heightSD i me E n unlogall unfix etc longitudeValue heightValue latitudeSDValue longitudeSDValue heightSDValue Exception h e toString b inputText getText yos s 83 A Real Time Kinematic GPS System Via the Internet labelSix setText if command length 0 labelSeven setText ERROR Empty Command Not Submitted else labelSeven setText Submitted command SimpleWrite sw new SimpleWrite sw messageString command inputText setText latitudeData setText Latitude longitudeData setText Longitude heightData setText Height latitudesDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard Deviation 84 f A Real Time Kinematic GPS System Via the Internet File name SimpleRead java Purpose To read data from the Serial Port import java io import java util import javax comm public class SimpleRead implements Runnable SerialPortEventListener Static CommPortIdentifier portId static Enumeration portList InputStream inputStream SerialPort serialPort Thread readThread public static void main String args portList CommPortIdentifier getPortIdentifiers while portList hasMoreElem
53. f rapid development and simply code reuse 5 2 Tradeoffs The tradeoff for this portability is that Java does not utilize any specific platform strengths such as OpenGL or QuickDraw 3D It performs all of it s graphics through the Abstract Windowing Toolkit AWT For most simple applications this is not a problem but many are yearning for a more robust graphics toolkit or access to platform specific routines 23 A Real Time Kinematic GPS System Via the Internet 5 3 Network Savvy Figure 5 1 The Protocole Stack Protocol Hierarchy Higher Protocol level Lower Java comes with a complete library for network applications which make it easier for the programmer to deal with protocol from the lower level like TCP IP to the higher level HTTP FTP A protocol consists of all the rules that two computers or two programs need to know to communicate over a network Chancogne amp Austin 1996 Figure 5 2 The Client Server Architecture SEVEN Ar wtecoiurae Nem irterr st I x Xzz Ger Saian SVL LL ot Tob THLLS ITE wee Tasks like client server connections and access to remote objects on the Internet become easy Opening a specified URL Uniform Resource Location somewhere on the net with Java is as easy as opening a local file on the system 24 ees A Real Time Kinematic GPS System Via the Internet Figure 5 3 The Java compiling and running scheme Java compiling s
54. following section analysis different Internet connection speed and Internet protocol to see whether they satisfy the requirement of Real Time Kinematics listed above This is important because if any of these requirements not satisfied the Rover receiver would either compute an inaccurate location or could not compute its location at all All tests were conducted at different times of the day on Monday 16th Tuesday 17th and Saturday 21st September 2002 A summary of these test results is listed in the tables below For a list of full test results please refer to the Appendix D Reminder Time taken for each packet microsec 1 000 000 x bytes bytes Speed bits sec 8 For Local Area Network LAN Note Some LAN only support up to 10Mbps But in our experiment the network support up to 100Mbps But similar result would be expected with 10Mbps Local Area Network UDP Unicast connection From UNSW Residential college 129 94 199 101 100Mbps To UNSW EE Blue Tooth lab 149 171 37 185 100Mbps Packet size Unicast speed Packet travel time Packet error rate 256 bytes 2 84 Mbps 0 7 ms 0 6 512 bytes 3 37 Mbps 1 2 ms 2 396 1460 bytes 5 83 Mbps 2 0 ms 6 196 46 A Real Time Kinematic GPS System Via the Internet Local Area Network TCP IP connection From UNSW Residential college 129 94 199 101 100Mbps To UNSW EE Blue Tooth lab 149 171 37 185 100Mbps
55. for a wide range of applications including differential satellite positioning 7 2 DGPS Positioning over the Internet Internet can offer many advantages over the conventional radio data transmission method when it is used for differential satellite positioning Some of them are described in the following 1 Internet is not limited by an effective data transmission range therefore the rover station can be located at anywhere in earth as long as there is Internet connection available 2 It is also advantageous for differential positioning in regions with severe signal interference such as urban areas and for applications with a large number of rover users 30 ees A Real Time Kinematic GPS System Via the Internet The transmission time taken for the user to retrieve the differential correction data from the reference receiver station determines the differential data latency for the positioning Less than a few seconds of data latency is typically required for most DGPS applications To achieve this Internet protocols should be carefully selected which defines how the data are transmitted through the Internet i e TCP IP or UDP 7 3 The Internet Protocol best suits DGPS The Transmission Control Protocol TCP and the User Datagram Protocol UDP are two important transport protocols that have been widely used for Internet applications TCP provides a stream delivery and virtual connection service to applications through
56. herefore clock errors in the receiver are hard to predict fe A Real Time Kinematic GPS System Via the Internet 3 Introduction to Data Networking 3 1 Open Systems Interconnection OSI Reference Model Introduction The OSI model has seven layers Each layer performs specific functions and communicates with the layers directly above and below it Higher layers deal more with user services applications and activities and the lower layers deal more with the actual transmission of information The purpose of layering the protocol is to reduce the design complexity and separate specific functions The OSI reference model is shown below Figure 3 1 The OSI reference model with network architecture t Exchange Layer Unit Application M Application Protocol Application APDU B Presentation Presentation Protocol PPDU 5 Session dM d Session Protocol_______ SPDU 4 Transport sowie epee oe TPDU 1 Physical Physical Physical Physical Bit ees A Real Time Kinematic GPS System Via the Internet 3 1 1 Layers Physical layer Physical layer Is concerned with the exchange of the individual bits over a medium Issues such as the how hardware being used what voltage and timing should represent a 1 or 0 are considered at this layer Data link layer Data link layer is responsible to ensure the reliable transmission of information units packets or frames so that it appears free of undetected tran
57. hesis group It was build based on the Dallas Semiconductor s Tiny Internet Interface TINI Microcomputer Generally smartGPS and TINI board mean the same thing 4 1 TINI board hardware details specifications Inside smartGPS hardware there is a TINI board of which the heart is a Dallas DS80C390 microprocessor running at a clock speed of 36 8 MHZ 4 1 1 The TINI Chipset The TINI board chipset consists of the following hardware Dallas DS80C390 microprocessor 10Base T Ethernet amp Network Interface Card Real Time clock for time stamping 512Kb Flash Read Only Memory for storage and execution of the runtime environment 1MByte total SDRAM with Li Cell an non volatiser circuit for RAM and file storage 4 1 2 The TINI Runtime Environment A runtime environment defines the services provided by software that describes hardware drivers protocol stacks APIs and all other functions necessary for developers to create their applications f A Real Time Kinematic GPS System Via the Internet The TINI runtime environment is stored in flash ROM so that the system maintains the code in the absence of power Flash memory ensures that the runtime environment can be easily updated but can t accidentally be deleted The TINI runtime environment is substantial Care has been taken to ensure that the developers can focus on creating applications as opposed to providing the layers of infrastructure necessary to execute code A g
58. hipment tracking service allowing them to check the exact location of their urgent shipments from collection to delivery at any time 9o T m sng lll RACK e track Steps to track the shipment locations 1 A shipment number and password will be issued when customer post their shipment 2 Courier company attachs a RTK GPS system on the document or parcel and start tracking 3 Customers can track their shipment using the company homepage via e track or mobile phone via sms track acknowledgement using the shipment number and password issued 26 fee A Real Time Kinematic GPS System Via the Internet 6 2 Allocation of Emergency resources Everybody knows 000 is an emergency hotline service to contact in life threatening or urgent situations Every minute Telstra Communications Centre receives many calls and has to arrange appropriate responses from a local police station or from other services e g Ambulance or Fire Brigade across Australia O00 EMERGENCY In a life threatening emergency dial 000 To response to accidents or crime scenes it is very important to locate the closest officers or emergency vehicles to the incident immediately But how do we know where and who are the closest officers If every police vehicle bicycle squad police horse and other emergency vehicle also install a RTK GPS system the control center will be able to know the exact location of officers and
59. irai daa o be accoptad andophamori depedmonut valo bo y Deed mah drant nga algemene od crite Set receives dynamics ECUTOFF EXTERNALCLOCK EXTERNALCLOCK FREQUENCY FI HEIGHT FOX POSITION FIX VELOCITY UNF ix FREQUENCY OUT FRESET HELP or LOCKOUT UNLOCKQUT UNLOCKOUTALL dynamics op on fuser dyramies ecutoft Set elevation cutoff angie Sets feta parameters of an optional extemal oscillator Sets clock rate externaiciock option external frequency clock rate DONE ER en MAR fix velocity v vy vz Remove all receiver FIX constrants untir able Clears ali data which is stored in non volatile mem Set up the RTK mode 76 BE A Real Time Kinematic GPS System Via the Internet SAVEALMA Save the latest almanac in non vokatils o saveaima aphon RER sender por st Sum Tomis isa setedh pr hu RESETHEALTH Reset PRN heih msetesthp enon Enable or disable time synchromzato imesync fog UNDULATION Choose undulation undulation y VERSION Current saltwere and hardware inlormalion version 77 fe A Real Time Kinematic GPS System Via the Internet Appendix B Developed Software File name GPSApplet version java Purpose To provide a friendly graphical users for users to enter Command and to track the Rover receiver position lt applet code GPSApplet class height 800 width 400 lt By Andy Au and Dona
60. ively small Out of the three UDP LAN connections since the connection with 1460 bytes packet size has a relatively large packet travel time and packet error rate so it is not a good choice On the other hand the connections with LAN UDP 256 bytes and LAN UDP 512 bytes also fully satisfy the Real Time Kinematic requirement When a Local Area Network is not fully reliable for example there are other network traffics it is better to use 256 bytes as the packet size because its packet error rate is smaller Otherwise LAN UDP with 512 bytes packet size is the best choice for RTK GPS out of all examined connections 50 A Real Time Kinematic GPS System Via the Internet A summary of the best selected connection link between Master and Rover receivers network performance supporting Real Time Kinematic is listed below Optimised Settings From speed To speed Type of connection Experimental Result Packet size Unicast speed Packet travel time Packet error rate 100 Mbps LAN 100 Mbps LAN UDP 512 bytes 3 37Mbps 1 2 micro sec 2 3 Tes BEY rime DETER Progress EN Overall BR REN D Figure 9 7 The LAN UDP 512bytes Connection speed Speed Mhisieac ert ute n pem m 51 ME A Real Time Kinematic GPS System Via the Internet 10 GPS Applet Controller 10 1 GPSolution The Master and Rover receiver that was us
61. ld Ying import java applet Applet import java awt import java awt event import java io import java net import java util public class GPSApplet30 extends Applet implements ActionListener final int port 6789 make this same as server port String servername localhost Socket clientSocket DataOutputStream toServer Grafix stuff Label latitudeData longitudeData heightData latitudeSDData longitudeSDData heightSDData Button bButtonOne bButtonTwo bButtonThree bButtonFour bButtonFive bButtonSix b TextField inputText Label label label2 labelOne labelTwo labelThree labelFour labelFive labelSix labelSeven int fileReadLine constants static final String connect Connect n public void init bButtonOne new Button Fix Master Receiver location Ww bButtonTwo bButtonThree new Button Logging Master Receiver data new Button Set DGPS timeout bButtonFour new Button Receive Data from Master bButtonFive new Button Logging Rover receiver data bButtonSix new Button Display Rover Location b new Button Submit Command label new Label labelOn new Label labelTwo new Label labelThr new Label labelFour new Label labelFiv new Label labelSix new Label labelSeven new Label 78 A Real Time Kinematic GPS System Via the Internet latitudeData new Label
62. le range 35 tenes A Real Time Kinematic GPS System Via the Internet Figure 8 2 Correction Information Propagation Mode D Pee Reference Station Propagation Mobile i pents Chents The other advantage is the possibility of bi directional communication In this case a request from a user will be transferred to a reference station The reference station will supply the user with the corrections that will be formed upon his request These corrections will consist only of a subset of data which help to decrease an amount of information we need to transfer through the Internet The most important advantage of RTK via Internet is flexibility in the user requirements It means that the user can define the accuracy of the service and consumption of the bandwidth in his request H Hada K Uehara H Sunahara 2001 8 5 83 RTK Positioning Using Internet Protocol and GPRS in Italy There is a permanent station connected to Internet and real time correction message transmitted with IP protocol using a Linux server through the 2101 port which is assigned by IANA On the other hand rover station connected to Internet receives data with a client program on Pc or PDA linked to the RTK GPS receiver Testing of the GPRS protocol of GSM will be arranged if telephone companies are ready Details of this research cannot be discussed due to the lack of resources M Caprioli amp A Scognamiglio 2001 36 ME A Real Time Kinem
63. mitted every second but the bit rate is set too low data will overflow the serial port buffers and cause an error condition in the receiver status 55 f A Real Time Kinematic GPS System Via the Internet 10 4 1 Fix Master Receiver Location The reference station must initialize the precise position of its reference antenna phase center lat lon hgt This is accomplished by utilizing the GPSCard FIX POSITION command The fixed position in the following command is the antenna located at the rooftop of the EE building UNSW Command FIX POSITION lat lon height amp applet RRS GPSApplet30 class 3 ial x Applet GPSCard APPLET CONTROLLER Control master receiver Logging Master Receiver data Set DGPS timeout Submitted fix position 33 9 115 2 86 9 10 4 2 Logging Master Receiver data LOG stores or displays data on a communication port COM1 or COMO If the LOG syntax does not include a trigger type it will be output only once following execution of the LOG command If trigger type is specified in the LOG syntax the log will continue to be output based on the trigger specification Specific logs can be disabled using the UNLOG command whereas all enabled logs will be disabled by using the UNLOGALL command All activated logs will be listed in the receiver configuration status log RCCA Command LOG port data ontime seconds FE Applet GPSCard APPLET CONTROLLER
64. order to apply the Real Time Kinematics GPS technology the master and rover receivers have to be at least able to receive four of the same satellites Therefore there is a physical limitation between receivers Hence it is not practical to setup a master receiver in Sydney and a rover receiver in London because the correction message generated by the master receiver has no use for the rover receiver therefore the Real Time Kinematics technology cannot be used A practical range could be between Sydney and Newcastle for example Receivers can even setup at large bridges by comparing the extremely accurate computed results the slightly movement of the bridge can also be detected 43 s A Real Time Kinematic GPS System Via the Internet 9 5 Analysis TCP IP and UDP Traffic Software In order to analysis the TCP IP and UDP traffic two programs were used The first program was called LanMark XT Pro it is a shareware with 3 days trail period at http www layer1software com products network performance software pro Figure 9 5 The user interface of LanMark XT Pro LanMarkXT Console 192 168 1 100 hypertro kjwifn File View Testing Wizards Tools Help lol x fal S Ba x xc se aul v 4 Data UDP 256 Bytes Unicast m a Data TCP 1 O MByte d Data TCP 2 0 MByte amp Lad Data TCP 3 0 MByte Da Data TCP 4 0 MByte DA Data TCP 5 0 MByte H D Data UDP 1460 Bytes Broadcast d Data UDP
65. ort mode Control rover receiver Logging Rover receiver data Display Rover Location Submit accept com rtcm 57 f A Real Time Kinematic GPS System Via the Internet 10 4 5 Logging Rover Receiver Data The LOG function was explained in two pages before Command LOG port data ontime seconds F Control rover receiver Receive Data from Master i Display Rover Location Submitted log com1 prtka ontime 1 Note for PRTKA Type Positioning Trigger ontime or onmark 10 4 6 Display Rover Location When this button is pressed the Rover location would be displayed in the table at the bottom of the applet It gets the data from the Rover receiver Figure 10 4 A sample of the logged data from the Rover receiver By using the Java Communication package javax comm the RS 232 serial communications port which is a low level made available by the underlying system SerialPort defines the required functionality for serial communication ports This applet reads the logged data from the serial port and converts them into type String By using array it then selects the useful information and displays them in the table There are two ways this button can work Displaying logged data from COM1 or COMe in real time Displaying logged data from a file which has been saved 58 f A Real Time Kinematic GPS System Via the Internet Control rover receiv
66. ources sss 27 6 3 Recreational Users eseseeeeeeeeseeeeeeneee 28 Research on Real Time Kinematics GPS sse 7 1 Background to DGPS ico E e eb RO ade ae 29 7 2 DGPS Positioning over the Internet 30 7 3 Thelnternet Protocol best suits DGPS 31 Real Time KInemalics c cues cine MEO eu Rindeac scias eei ices 8 1 RIK PrIDOIDIS ien EE ooo PDA RERO Yol aat xi E Rd 32 8 2 Temporary Master Station eese 33 8 3 Permanent Master Station ccceeeeeeee ee eeeeeeeeeeees 33 8 4 INGIWORGCH IK iio E ous eure ie ees 33 8 5 Different approach on DGPS and HRTK 34 8 51 EURE E m 34 8 5 2 Differential and RTK corrections for the Internet Car 35 8 5 3 RTK Positioning using Internet Protocol and GPRS 36 854 SWEPOS ae ein ntt bate E EEE A estes 37 Communicate between GPS receivers eere 9 1 Use of Radio Modem esses 38 92 Converting UDP PacKOl 2 d La ee Ea e totem 39 9 3 UDP Packet Travel TiIilg ioo ta ren orto t YE ste 41 9 4 Real Time Kinematics GPS System Requirement 42 9 5 Analysis TCP IP and UDP Traffic Software 44 9 6 X Packet Travel Time Measurement ssssssss 46 9 7 Packet Travel Time Analysis sssseeeeseesees 48 GPS Applet Controller
67. raphical representation of the TINI runtime environment is illustrated below Figure 4 1 The Layers of the TINI Runtime Environment Java Java Application Application Native Methods TINI OS Process amp Thread Schedulers 1 0 Subsystem Memory Subsystem TCP IP 1 0 Manager File System Manager Network Device Heap Garbage Drivers Drivers Manager Collector eet A Real Time Kinematic GPS System Via the Internet 4 1 3 Supported Application Program Interfaces APIs The most recent version of Sun s Java Development Kit JDK API at the time of writing is version 1 4 1 TINI provides full support for the JDK API version 1 1 Some of the classes from later API versions have been supported where they have been deemed useful and relevant to TINI applications Sun also provides a Java Communications API which is designed to provide access to communications devices such as serial and parallel ports This is supported by TINI A third API includes code that is specific to TINI It provides classes to access hardware and resources such as the Real Time clock and TINI operating system It is often considered good practice to minimise the use of TINI specific code This ensures that programs can be tested on a non TINI system and easily ported to other Java embedded microcomputers 4 1 4 The TINI Java Virtual Machine The TINI JVM is less than 40Kb in size All primitive types are supported So too are threads al
68. rtunately this kind of error can be minimized by using differential GPS which will be discussed in details in chapter 7 Satellite orbits Inhomogenity of earth s gravity field tidal effects from moon and sun solar pressure and relativistic effects can cause malfunctioning of satellites So there are orbit biases which will affect the accuracy of GPS Multipath This kind of error caused by the fact that the signal may be reflected by a nearby surface before reaching the GPS antenna Interference between reflected signal and direct signal will result incorrect carrier phase measured value Multipath error is hard to avoid and detect indeed ad A Real Time Kinematic GPS System Via the Internet Noise Random noise always exists in the measurement even all above mentioned errors have been correctly modeled therefore same position measure can be obtained everytime Measurement noise is about 0 to 10 meters while pseudorange noise for carrier measurement is 0 2 to 5 millimeters Obstruction Building trees or any other tall and big object can cause obstruction when using GPS outdoor Poor or even no positioning readings may occur due to obstruction error Clock Satellite clock and the receiver clock are very important when calculating the distance between satellite and the receiver Regardless of the extremely stable performance of the satellite clock because normal receivers use less expensive quartz clocks t
69. smission errors to the network layer Network layer Network layer concerns with controlling the operation of the subnet Processes like packet routing congestion control protocol conversion are involved in this layer Transport layer Transport layer provides reliable transparent transfer of data between terminals It isolates the upper layers from the inevitable changes in the underlying technologies Multiplexing flow control and broadcasting messages can be done at this layer The protocol used may be Connection oriented connection established between sender and receiver messages are sent over a fixed route the connection is released Messages arrive at the destination in order ees A Real Time Kinematic GPS System Via the Internet Connectionless information parcels are routed to their destination individually in order to utilise the most efficient link at the time Messages may need to be re ordered at the destination 3 1 2 Session layer Session layer provides enhanced services useful in some applications It manages dialog control and provides the control structure for the communication between applications Presentation layer Presentation layer provides certain functions that are requested It is concerned with the syntax and semantics of the information A network standard presentation is also provided at this layer Application layer Application layer works directly wi
70. t MASTER REFERENCE J STATION MOVING ROVER STATION ONE MOVING ROVER STATION TWO E v A Real Time Kinematic GPS System Via the Internet 2 Introduction to Global Positioning System Global Positioning System GPS is a satellite based scheme which can provide users with highly accurate latitude longitude altitude and velocity measurements It is available globally at anytime anywhere and any weather as long as the receiver is in view of the satellites GPS satellites travel at an amazing speed at about four kilometers per second even faster than a speeding bullet Figure 2 1 Twenty four GPS satellites orbiting around the earth This technology was initially developed by the US Defence Department one part of this system is reserved for military purposes while the other part can be used by anybody for free simply by the purchase of a GPS receiver 2 1 How does GPS work There are 24 GPS satellites orbiting at about 20200 kilometers above the earth s surface this allows 4 or more satellites in view from anywhere at any instant These satellites transmit two microwave with frequencies L1 1575 4MHz and L2 1227 6MH2 traveling at the speed of light approximately 300 000 km s tenet A Real Time Kinematic GPS System Via the Internet By multiplying the signal s travel time from the satellite to the GPS receiver with the speed of light we will know the distance between the satellite and the receiver
71. t fast enough packet travel time is long or not accurate enough packet error rate is large it will directly affect the accuracy of the computed Rover receiver position 61 PE A Real Time Kinematic GPS System Via the Internet 11 Thesis Project Promotion 11 1 Website In order to share the achievements of the thesis project with other research fellows and future students a website is created and located at http geocities com gps_thesis Figure 11 1 A Real Time Kinematic GPS System via the Internet Website XEM E aifgix J Meen Mew Fees Toe te 12 Ge O r rn ome IR X 0 MS Address fpc iquocties carr gos therm foton Artis g i A Real Time Kinematic GPS System Via the Internet salsas haai sieua i e wc poro Real time kinematic RTK is a high precision GPS based positioning technique that requires raw carrier phase data to be transmitted from a base GPS station to the mobile GPS receiver via a data link with very low latency This thesis project wil investigate protocols and hardware for using the Internet to deliver such data to the mobile receiver Investigations will involve both the wired and the wireless internet itis carried out by two fourth year undergraduate electrical and telecommunication students Andy Au and Donald Ying They are working under supervison of academics from the University of New South Wales Australia MASTER STA The
72. tIdentifier portList nextElement if portId getPortType CommPortIdentifier PORT_SERIAL if portId getName equals COM1 if portId getName equals dev term a try serialPort SerialPort portId open GPSApplet 2000 catch PortInUseException e try outputStream serialPort getOutputStream catch IOException e try serialPort setSerialPortParams 9600 SerialPort DATABITS_8 SerialPort STOPBITS_1 SerialPort PARITY NONE catch UnsupportedCommOperationException e try outputStream write messageString getBytes catch IOException e 87 f A Real Time Kinematic GPS System Via the Internet File name GPSApplet html Purpose To display the file GPSApplet class in a website lt html gt lt head gt lt title gt GPS Applet Control Panel lt title gt lt body background background gif gt lt center gt lt table gt lt tr gt lt td gt lt hr width 700 gt lt font size 2 gt lt b gt lt center gt GPS Applet Control Panel lt center gt lt font gt lt hr width 700 gt lt applet code GPSApplet30 class width 700 height 500 gt lt applet gt lt p gt lt td gt lt tr gt lt table gt lt center gt lt body gt lt html gt 88 FE A Real Time Kinematic GPS System Via the Internet Appendix C Logs Summary File name GPSCard log Purpose Contain all the information provided by the GPS receiver
73. th the user or application programs It provides access to the OSI environment for users It is called application layer because it contains network applications For example electronic mail file transfers virtual terminal protocols and distributed system etc ud A Real Time Kinematic GPS System Via the Internet 3 2 Transmission Control Protocol Internet Protocol TCP IP TCP IP is a suite or protocols which do not have session and presentation layers it is a standard for communications on the Internet The difference between OSI model and the TCP IP is shown below OSI TCP IP TELNET FTP HTTP DNS Application etc Presentation Session Transport TCP UDP Network IP Data Link Physical Internet Protocol IP The Internet Protocol is used at the network layer Sometimes it referred to as the Internet Layer in the TCP IP model In IP each machine or host is identified using a 32 bit number called and IP address A header is appended to the data coming from the data link layer creating an IP datagram The source and destination IP address information about the header and data length a checksum and data required to reconstruct the messages are included in the IP header ad A Real Time Kinematic GPS System Via the Internet Internet protocol performs three main functions which are routing datagrams through the Internet identifying data sour
74. though only 16 can be executing at once 4 1 5 TINI System Architecture The interaction of the TINI hardware devices runtime environment and networking interfaces are illustrated in the block diagram on the following page Fee A Real Time Kinematic GPS System Via the Internet Figure 4 2 TINI System Block Diagram ary i DS80C390 4 Parallel Ethernet Real Time Controller Clock 4 1 6 TINI Software Development TINI code is developed on a desktop machine and sent to the TINI when complete The TINI SDK includes serial FTP and TELNET servers By default commands to start these servers are included in the startup files The server facilities make it easy to upload and execute TINI applications The supported APIs are installed on the TINI at the same time as installing Slush The APIs also installed on the development machine in the appropriate directory This means that code can be compiled without error on the development machine rather than the TINI itself Hence TINI hardware costs are minimised and the programmer can develop on a machine with which they are comfortable and familiar s A Real Time Kinematic GPS System Via the Internet 4 1 7 Compiling and Running Java Code on the TINI An executable file must be produced from the class files for a program before it can be run on the TINI The process for building the TINI executable is similar to zipping up the class files using a compression program
75. tudeSDValue String longitudeSDValue String heightSDValue P fileReadLine fileReadLine 1 SimpleRead code new SimpleRead String data new String 125 BufferedReader stdin new BufferedReader new FileReader GPSCard log BufferedReader stdin new BufferedReader new InputStreamReader code inputStream for int i 0 i lt 125 itt String currentLine stdin readLine if currentLine null break StringTokenizer st new StringTokenizer currentLine data i st nextToken if data fileReadLine charAt 1 P for int i 0 i lt 15 i latitude i data fileReadLine charAt 33 i for int i 0 i lt 15 i longitude i data fileReadLine charAt 49 1 for int i 0 i lt 7 i height i data fileReadLine charAt 65 i For int 1 0 i 6 t latitudeSD i data fileReadLine charAt 83 1 for int i 0 i lt 6 i longitudeSD i data fileReadLine charAt 90 1 for int i 0 i lt 6 i heightSD i data fileReadLine charAt 97 1 if data fileReadLine charAt 1 R For int i 0 i lt 15 itt latitude i data fileReadLine charAt 26 1 for ant r 0g r 15 a i longitude i data fileReadLine charAt 42 1 for int i 0 i lt 7 i height i data fileReadLine charAt 58 i F a
76. ve is below ellipsoid 12 datum ID Current datum see Appendix G Page 234 13 1 lon soln z i 1 lat Standard deviation of latitude solution element in meters 1 Standard deviation of longitude solution element in meters 6 7 eid E 1 19 ide Pecenieimepeceae 3 5 8 0 0100 ICRIILF 89 A Real Time Kinematic GPS System Via the Internet File name GPSCard log Purpose Contain all the information provided by the GPS receiver Extracted from the GPSCard log SRTKA 154 266189 00 5 5 5 33 91776928983 151 23182335809 86 9710 0 0000 61 0 0074 0 0091 0 0256 0 0 4 1 1334321 2E RTKA Structure SRTKA week seconds i sv ff high L1L2 high lat lon hgt undulation datum ID lat SdDev lon SdDev hgt SdDev soln status rtk status posn type dyn mode stn ID xx CR LF Field Field type Data Description Example Log header GPS week number GPS time inin the week in seconds 6 7 lat Latitude of position in current datum in decimal fraction format A negative sign plies South latitude Number of matched satellites above RTK mask angie observations from satellites ben on ne rs kroer oL REM Number of matched satellites above RTK mask angle wih both L1 and L2 available 51 11358039754 Longitude of position in current datum in decimal
77. vehicles therefore able to allocate the best resources to save lives This might save up to one minute compare to the conventional police communication method which is very valuable in life threatening or urgent situations 27 f A Real Time Kinematic GPS System Via the Internet 6 3 Recreational Users Imagine there is a powerboat race installed with a RTK GPS system Every powerboat would have a GPS receiver as well as a transmitter to transmit data to the master station Therefore a website can be created to continuously update each powerboat position Hence event officials and powerboat fans will be able to follow the race closely without having to rely totally on helicopters Many individuals who love hiking fishing mountain biking driving recreational aircraft or bush walking are interested to know their exact location height and speed By the use of the RTK GPS system they will never get lost even in a foreign area again Furthermore knowing the moving speed for hikers or mountain bikers will allow them to adjust their routes according to their schedule and physical strength 28 Fe A Real Time Kinematic GPS System Via the Internet 7 Differential GPS Positional over the Internet DGPS DGPS is to cancel reduce the error sources in the GPS environments due to inaccurate GPS satellite clock and orbit data atmosphere effects as well as GPS satellite and receiver related biases 7 1 Backgroun
78. w SimpleWrite sw messageString log com2 RTCAREF ontime 10 labelOne setText labelTwo setText Submitted log com2 RTCAREF ontime 10 labelThree setText labelFour setText labelFive setText labelSix setText labelSeven setText e g unlogall unfix etc latitudeData setText Latitude longitudeData setText Longitude heightData setText Height latitudeSDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard Deviation else if e getSource bButtonThree SimpleWrite sw new SimpleWrite sw messageString dgpstimeout 2 300 labelOne setText labelTwo setText 80 A Real Time Kinematic GPS System Via the Interne labelThree setText Submitted dgpstimeout 2 300 labelFour setText labelFive setText labelSix setText labelSeven setText yg e g unlogall unfix etc latitudeData setText Latitude longitudeData setText Longitude heightData setText Height latitudeSDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard Deviation else if e getSource bButtonFour SimpleWrite sw new SimpleWrite sw messageString labelOne setText labelTwo setText labelThree setText labelFour setText labelFive setTe
79. website contains six sub pages with a guest book Home General description of the thesis project Develop Contain the full development plan step by step Challenges and possible risks 62 ad A Real Time Kinematic GPS System Via the Internet Application Listed the three possible market applications Courier service Emergency service allocation amp Recreational users Download Project proposal Final report Source code files and GPSCard menu can be downloaded here Useful links to other website are also provided Photos A photo collection of the equipment used in the project with brief descriptions Applet The GPSApplet Controller is put here but it cannot be used to control the Master or Rover receiver unless all the settings required are correct 11 2 Promotional CD A CD has been produced and attached with this report it contains the proposal final report all the software developed and the user manual of the GPSCard This should be very useful for the people who are interested at our project especially future students 63 Fee A Real Time Kinematic GPS System Via the Internet 12 Further Development The aim of the system is to provide accurate rover GPS receiver locations by using Real Time Kinematic technology Looking at the system diagram below there is nothing can be changed on the GPS receivers radio modems and the Internet protocols TCP IP or UDP But there are some further developments on the T
80. xt labelSix setText labelSeven setText accept com2 rtcm Submit accept com2 rtcm e g unlogall unfix etc latitudeData setText Latitude longitudeData setText Longitude heightData setText Height latitudeSDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard Deviation else if e getSource bButtonFive SimpleWrite sw new SimpleWrite sw messageString log coml prtka ontime 1 labelOne setText labelTwo setText labelThree setText labelFour setText labelFive setText Submitted log coml prtka ontime 1 labelSix setText labelSeven setText e g unlogall unfix etc latitudeData setText Latitude longitudeData setText Longitude heightData setText Height latitudeSDData setText Standard Deviation longitudeSDData setText Standard Deviation heightSDData setText Standard Deviation else if e getSource bButtonSix try char latitude new char 15 char longitude new char 15 char height new char 7 char latitudeSD new char 6 char longitudeSD new char 6 char heightSD new char 6 String latitudeValue SW ON 81 t A Real Time Kinematic GPS System Via the Internet String longitudeValue n String heightValue u String lati
81. ydney 203 173 128 88 33 6kbps To ihug 56kbps modem Randwick Sydney 203 173 131 70 56 6kbps Packet size Packet travel time Packet error rate 256 bytes 135 ms 0 0096 512 bytes 178 ms 0 0096 1460 bytes 311 ms 0 00 Note The theoretical upload speed for a 56kbps modem is 33 6kbps not 56kbps 9 7 Packet Travel Time Analysis Out of these 18 connections in order to select the best connection path we need to consider the following factors Packet travel time Connection reliability 48 ees A Real Time Kinematic GPS System Via the Internet Packet travel time To select the best path as a communication link between the master and rover receiver the packet travel time has to be less than or around 2ms 0 02 second In the above experiments all Local Area Network connections passed this requirement range from 0 7 to 2 6 ms but failed for communications which involved other networks or modem range from 75 to 102 ms Connection reliability There were two types of Internet protocols being examinant TCP IP and UDP As expected there is no packet error founded in any of the TCP IP connections However for UDP as the size of the packet increase from 256 to 1460 bytes or as the connection speed becomes slower from 100 Mbps to 56 kbps the packet error rate increases proportionally For Real Time Kinematic the packet error rate has to be less relatively small otherwise the computed

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