Timing principles in NaviPac
Contents
1. The timestamp of the telegram is now t0 minus dT This time can hereafter be corrected by a fixed latency age value defined under a property called Fixed age or Latency in the specific instrument s setup as can be seen below in Figure 1 F3 NaviPac Configuration File View Options Tools Help Setup File C SEIVANNAVIPACSDBNGENSETLP DB E File header I O Mode E Q Instruments i 4 Surface navigation 5 4 RR Geco Prakla GPS 1 v B Artemis driver 2 se PPS F Ashtech GFS Use time in telegram hh mm ss Free Position input Fixed age D 12 A GPS3 NMEA a B JB AGA Geodimeter Geoidal height HI Gyro 3 Easting C O Om El ge Motion sensor Northing C O Om a g Doppler log Send file E Dynamic positioning 3 gd Special input Does your GPS system have a known fixed age E e Data output 1 The entered value will be subtracted from the NaviPac time stamp Please use carefully E 481 Data acquisition E 2 Offsets 4 Saving set up file C SEPZASN avi PacsDB asnsetup D B E l e Geodesy 23 04 2014 13 13 38 Start Navigation Saving set up fle C EMVASNAVIPAC DB GENSETUP DB O Projection A 5 0 Borneo x Ellipsoid International 1324 Datum shitt None Stopped Ed Status Auto Manual Save 1 Fixed age property for a GPS instrument There are some GPS instruments eg NMEA GPS that manage to output data in real time which means that the p2. Page 12 of 30 EIVA MARINE SURVEY SOLUTIONS 4 3 PPS Indicator The PPS is as mentioned above implemented by assigning the pulse to the ring pin on the physical serial port GPS COM port DB25 TxD 3 RxD Gnd 7 Gnd PPS Coax Shield 7 Gnd PPS Coax Centre 22 RI Table 1 DB25 PPS configuration To test the cable you can connect the GPS to the COM port with the cable then start the NaviPac Configuration setup program From here select Test Interface Ports from the bottom of the Tools menu and select the port in use The NaviPac Rawdata window should now display the following lt Ring gt GPZDA Ring GPZDA Ring GPZDA Ring GPZDA Ring Ring can occur more than one time between ZDA telegrams as a PPS has a certain width for an Ashtech Z12 instrument approximately 2 milliseconds which might result in more interrupts EIVA MARINE SURVEY SOLUTIONS In some interfaces we have observed that the ring indicator is not connected to the PC and in that case you may use the DSR signal instead This can be changed under Options Global Parameters Advanced PPS Pin Specify Global Parameters NaviPac GPS Filters Height Calculations UW and Remote Navigation Advanced Which pin on the serial port must NaviPac use for PPS detection RING Typically over pin 3 of a nine pin DB9 serial port or pin 22 over a 25 pin DB25 port DSR Data set read
3. 1 Kongsberg HiPAP APOS and Kongsberg Hain eeeeeeeeeeeeeeeeeeeeeeeeeeeeeaaaees 23 02 Remol Pos araronce Gaeerces en Um 24 89 OREBAPS DPORE errereen E E ee EE eee ee eee eee eee 25 8 4 PHINS ROVINS Position citus ina arent rud asa and usa Sant snas ea bis av na x end eus antc o neas nuns 26 8 5 Sonardyne USBL GPSONUSBL ccccccccececeeeeeeeeeeeeeeeesseseeececeeeeeeeeeseeeeeaaaaas 27 EIVA MARINE SURVEY SOLUTIONS AMEN rs mt t 28 TIU ES Oe VUNG ousdcosiedienamsdssnixiiskurtiusdutiM a akkiumuta enel dd ia UNUM NUEx ERU des EENEN EERS 28 10 1 Checking calculated latency sssessessssseessseseeseee nennen nnne nnns 28 10 2 Testing of time synchronisation ccccccssscecceeseeeccesececseeseeeseeseeessauseesseeseeesseeeeses 29 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 3 of 30 Page 4 of 30 EIVA MARINE SURVEY SOLUTIONS 1 Fundamentals NaviPac has a dedicated background process DatalONT to handle all data collection and time tagging The process is kept as simple as possible as it runs on the Windows OS real time queue All other processes are handled by the ordinary process queue and thus given a lower priority For each input port in use the process creates a thread ie a process to handle the communication Each thread reads data from the port collects it into packets and stores data and time in a dedicated
4. Objects amp zZDA hhmmss ss dd mm yyvyy z1 22 hh E Warm start lt CR gt lt LF gt Bl a Data output 1 j 9n Saving set up file LSEPASMaviPacsDB aenset a 23 04 2014 13 13 38 Start Navigation Saving set up file SEPZASMAVIPBACSDBSGENS Stopped Ed Status Auto Manual Save Figure 5 Setting up NMEA ZDA time synchronisation You must hereafter manually specify for each individual applicable GPS instrument whether it must use time in telegram EIVA MARINE SURVEY SOLUTIONS NMEA ZDA telegram implementation The driver in NaviPac that uses ZDA and PPS telegrams for synchronisation is implemented roughly as follows The port drive is set up to interrupt on PPS ring indicator and lt CR gt lt LF gt On PPS e Register time of PPS into timestamp e fa proper hh mm ss exists as defined below in regards to lt CR gt lt LF gt A ZDA telegram read after the PPS then hh mm ss 1 equals timestamp Set the PC time to hh mm ss 1 and ms 00 On lt CR gt lt LF gt e Read the telegram from the port e fthe telegram is the correct ZDA telegram read time in telegram as hh mm ss three two digit numbers not fractions Potential errors If the ZDA telegram is outputted too long after its corresponding PPS telegram the time synchronisation probably will lose track and fail as there are no tools to match PPS and ZDA 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 11 of 30
5. Tools Help Setup File CAEIVANNAVIPACADBNGENSETLIP DB amp f File header EE Instruments I O Mode B iA Surface navigation B 4 Driver details 0E Geco Prakla GPS 1 Apr dotum dift oe Artemis driver 2 Use PPS B Ashtech GPS1 E Free Position input Use time in telegram hh mm ss E GPSS NMEA Fixed age al m AGA Geodimeter Geoidal height Om 5 5 Gyo ES om Hig Motion sensor il E 7 Doppler lag a EX m fa Le Dynamic positioning 3 Send command file LI EN m g Special input File name NONE m Data output 1 H 8 Data acquisition Must NaviPac use the timestamp in the NMEA telegram to establish when the position was valid E29 lfsets 4 NOTE Requires that the NaviPac pc is synchronized ae Geodesy with GPS dock Projection R 5 0 Bornes Saving set up file C MEMVA NaviPac DB Gensetup 0B Elipsoid Intemational 1924 23 04 2014 13 19 38 Start Navigation Ge Datum shift Mane Saving set up file C SEPZASNAVIPACSPBSRGEMSETUP _L scale metric p 5 Objects idl H 0 Warm start Status Auto Manual Save Figure 3 Time selection for GPS supporting use of time synchronisation To do so the PC running NaviPac must be synchronised in time with the GPS clock This can be done either via interfacing into NaviPac as discussed in the fo
6. UTC time PPS Saving set up file CEM AN aviPac OB Genset a 23 04 2014 13 13 38 Start Navigation Saving set up file C SEPZASNAVIPACSDBSGENS Stopped ES Status Auto Manual Save Figure 4 Setting up Trimble UTC time synchronisation In NaviPac you select Trimble UTC time PPS as a special input on a separate dedicated COM port The PC time is then automatically synchronised with the GPS clock You must hereafter manually specify for each individual applicable GPS instrument whether it must use time in telegram EIVA MARINE SURVEY SOLUTIONS Trimble UTC telegram implementation The driver in NaviPac that uses UTC and PPS telegrams for synchronisation is implemented roughly as follows The port drive is set up to interrupt on PPS ring indicator and lt CR gt lt LF gt On lt CR gt lt LF gt e Read the telegram from the port e lf the telegram is the correct UTC telegram read time in telegram as hh mm ss three two digit numbers not fractions On PPS e Register time of PPS into timestamp e fa proper hh mm ss exists as defined above in regards to lt CR gt lt LF gt a UTC telegram read prior to the PPS then hh mm ss equals timestamp Set the PC time t
7. in telegram hh mm ss r3 NaviPac Configuration File View Options Tools Help Setup File CAEIVASNAVIPFACKDBYGENSETUP DB Edited lB File header Offsets Z z 9 Instruments I O Mode POE A Surface navigation 5 18 TA E 8 5 Gyro 3 a Motion sensor UW hold time a g Doppler log Gyro add B O Dynamic positioning 3 Roll add angle ea H Kongsberg LBL Pama DURS Pitch add angle Kongsberg HIPRAPYAPOS j 27 kongsberg Hain 5 Special input 1 Cel mip Data output 1 H 8 Data acquisition 5 9 Offsets 4 B TA Geodesy E 5 Objects E Warm stark Range tolerance Use stacked surface nav Use time in telegram hh mm ss Use binary HiPAP telegram Free object hold time Transceiver Id Use this USBL unit for differential USBL 4 NOTE Requires that NaviPac and HiPAP APOS is synchronised in time Saving set up file C SEPZASMaviPacsDB aensetup DB 23 04 201 4 13 13 38 Start Navigation Saving set up file E SEPZASMAVIPACSDBSGENSETUP DB Stopped Status Auto Manual Save Figure 8 Time selection for Kongsberg HiPAP APOS instrument Similar for the dual HIPAP APOS SIMSSD telegram 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 23 of 30 EIVA MARINE SURVEY SOLUTIONS 8 2 Remote GPS F3 NaviPac Configuration File View Options Tools Help Setup File CAEMA NaviPac DB Gensetup DB fl Fie header E A Instruments oO He A Surface navig
8. input of ZDA PPS Please read the special manual on GPS time tagging before using this solution COM41 9600 N81 EJ J I O Mode On Saving set up file E EPASMNaviPac D B aensetup D B r 23 04 2014 13 13 38 Start Navigation Saving set up file SEPZASMAVIPACSDBSGENSETLHP DB Stopped Ww Status Auto Manual Save Figure 7 Using GPS PPS directly on each instrument The cable from the GPS to NaviPac must be designed to handle data and pulse simultaneously similar to the time telegram pulse discussed above in Section 4 3 PPS Indicator NaviPac will hereafter timestamp the signal based on the PPS and not based on reception of the first byte as is normally the case This is implemented based on reception of one PPS followed by zero or more GPS telegrams per second All GPS telegrams received after a PPS will be time tagged with the PPS time Problem If the latency is longer than one second eg old Leica with more than two seconds NaviPac cannot use PPS as standalone see Section 4 2 Using NMEA ZDA telegram EIVA MARINE SURVEY SOLUTIONS NaviPac has a partial solution for handling latencies slightly longer than one second Let tMin determine an absolute minimum GPS calculation time that is the fastest possible output If NaviPac receives a data set from the GPS and calculates the difference between reception time T now transmit time and the latest PPS then the resu
9. 0 8340E 0066 02 2 0 0 06 0 31 38 3 0 0000E 00 19 04 13 14 18 16 24 RTK telegram Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input e By external clock synchronisation that is by synchronising PC time with the GPS clock see Section 4 Synchronising with external clock You should avoid combining any of these methods 8 Dynamic positioning instruments with timestamp NaviPac time tags all incoming dynamic positioning telegrams USBL LBL remote GPS etc on reception of the telegram as discussed in Section 2 Simple timing For some drivers this may be overruled by using timestamp information in the telegram EIVA MARINE SURVEY SOLUTIONS 8 1 Kongsberg HiPAP APOS and Kongsberg Hain For the Kongsberg HiPAP APOS and Kongsberg Hain dynamic positioning instruments timing accuracy may be improved by synchronising NaviPac and the dynamic positioning instrument with a GPS The SIMSSB telegram from the HIPAP APOS instrument SPSIMSSB hhmmss ss tp Status error coord orientation sw x y depth lt cr gt lt lf gt includes hereafter the time of position validity NaviPac can be set up to use this timing information This is done in the lower part of the instrument setup by selecting the property Use time
10. ARINE SURVEY SOLUTIONS If you want to check the synchronisation further it is a good idea to start the NaviPac Alarm Monitor Online gt View gt Alarm Monitor Tye Limit vv Alarm Count Reference NavPac Error LEIDEN ENSURE ees eee eee Naviac Warning 0 000 0 000 0 000 0 000 Naviac Dea 0 NaviScan Info 0 000 0 000 0 000 0 000 GPS 1 Non RTK Input 0 000 0 000 0 000 0 000 Message 0 000 0 000 0 000 0 000 Oo mM dao Figure 14 Alarm Monitor data In addition to normal messages alarms errors and warnings this module includes messages regarding the time synchronisation e UTC ZDA Port xx PPS received without incoming telegram PPS received multiple PPSs have been received since last telegram e String discarded T tttttt PPS ppppp PPS Count xx String received multiple PPSs have been received since last string e UTC ZDA Port No PPS received for yyy ms Telegram received but it is a long time since NaviPac received a PPS e UTC ZDA Port No PPS received Telegram received but NaviPac has never received a PPS e PPS Time has not been performed for xx cycles Check if UTC telegram is correct PPS received but could not synchronise the clock e First update time from hh mm ss sss to hh mm ss sss NaviPac has synchronised the time for the first time e hh mm ss PPS Time sync received on strange time hh mm ss sss The PPS corresponding to time first hms was received but the clock differs to
11. EVA MARINE SURVEY SOLUTIONS NAVIPAC TIMING PRINCIPLES Author Ole Kristensen Last update 26 06 2014 Version 3 9 Page 2 of 30 EIVA MARINE SURVEY SOLUTIONS Contents MES 2 0 o dronni innn n E A A A m 4 EE O ANE 4 3 Timing supported by external information about latency of data 6 4 Synchronising with external clock 111 eeeeeeeeeeee eee eeeee eene nennen 7 4 1 Using Trimble UTC telegram esssseseeeeeeeneeeneeennnnn nnne 8 4 2 Using NMEA ZDA telegram seeeesesseseeseeeeeeennn nnne nnne nnns 10 AOS PEO IDOC 19 mmm 12 5 Assigning PPS to specific position input ccseeeeeeeeseeeeenseeseenseeeseenseeseneseeees 13 b H commended melliot eeisenskpekusdasissbusskFEKuEdas ks a 15 MEN ee uj me d 16 TW PRR E 16 ju 17 y MEE CI oat PRETI 17 18 Ll EEC v 18 7 6 POSMV Group ecccccccccscsesesesesececececececececececeseneseececevevevevevevevevevavavavavavaceveverenenenenenenen 19 Til PR CUKA v S 19 AO Ead SKY eer a E ee eee 20 Gad COIN 2O aa E E E 20 LAIO TOD COM e HP 21 Tea E MAMI OOO E E A E E E E T AS T A E E 22 8 Dynamic positioning instruments with timestamp 22 8
12. Longitude Quality NoSat DOP Height lt CR gt lt LF gt Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input e Locally by registering time of reception plus latency see Section 3 Timing supported by external information about latency of data for RTK only If you want to use external clock synchronisation that is the PC time synchronised with the GPS clock see Section 4 Synchronising with external clock you should use an NMEA driver instead of an Ashtech You should avoid combining any of these methods EIVA MARINE SURVEY SOLUTIONS 7 2 C Nav The C Nav driver in NaviPac supports two data formats e C Nav TRIN format 010201CNavV12 8 week time latency latitude longitude height 0 lt HDOP gt lt VDOP gt etc etc e NMEA GGA GGA time Latitude N S Longitude E W Quality Satellites HDOP Antenna Alt Unit Geoidal separation Unit Age Diff ID lt CR gt lt LF gt Timing of positioning data can be performed using the following scenarios e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input e HIN format Locally by register
13. POSMV Group The POSMV Group driver is purely based on time in the data format Timing of positioning data can be performed using the following method e By external clock synchronisation that is by synchronising PC time with the GPS clock see Section 4 Synchronising with external clock The interfacing will normally occur via the POSMVIF module see the dedicated manual on POSMVIF http download eiva dk online training NaviPac 20Manuals Various POSMVIF pdf for detailed information All other methods are invalid and should be avoided 7 7 Racal UKOOA The Racal UKOOA driver in NaviPac supports the UKOOA utilised ASCII data format e LVT utc data age datum latitude longitude height ukooa parameters cr lf Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input e Locally by registering time of reception plus latency see Section 3 Timing supported by external information about latency of data Most known installations use the latency in telegram mode 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 19 of 30 Page 20 of 30 EIVA MARINE SURVEY SOLUTIONS 7 8 Sea diff Skyfix The Sea diff Skyfix driver in NaviPac supports the following d
14. and iD WE GIC compensate the local timestamp for this Be Motion sensor 2 PE i D oppler log j E Dynamic positioning 4 p bs 10 06 2014 15 02 15 j 8 Special input Loading set up file C EIVA NaviPac DB Gensetup DB l ERC D ata output 2 8 Data acquisition 3 fl Offsets 4 stopped Ww EE aen Geodesy ae Objects Status Auto Manual Save Figure 2 Special handling of Ashtech GPS latency For example if the GPS outputs the value 1 73 s this means that the correction from base is 1 second old and that the position is 0 73 seconds old Problem This will only work for position latency of 0 99 seconds or less Note This is only valid for RTK GPS instruments like Geco Prakla Sea diff Skyfix and Racal UKOOA GPS use a similar approach EIVA MARINE SURVEY SOLUTIONS 4 Synchronising with external clock Another way of handling timing is to calculate the latency by setting the PC clock and then reading the time in the positioning telegram from the GPS instrument This calculation must then be enabled manually for each individual applicable GPS instrument under the Use time in telegram hh mm ss property as shown below in Figure 3 Eg NaviPac Configuration File View Options
15. ata format e 1123mmddyyHHMMSS S01 21N540853 17E0090000 00 0012 3111 1222 2111 1 222 233344455 566 677889991122333445566677889991234567891 111 1 lt CR gt lt LF gt Timing of positioning data can be performed using the following method e Locally by registering time of reception plus latency see Section 3 Timing supported by external information about latency of data All other methods are invalid and should be avoided 7 9 Sercel NS230 The Sercel NS230 driver in NaviPac is just a special variant of the NMEA driver and it supports the following data formats e GGA time Latitude N S Longitude E W Quality Satellites HDOP Antenna Alt Unit Geoidal separation Unit Age Diff ID lt CR gt lt LF gt e GGK UTC Date Latitude Longitude Quality NoSat DOP Height CR LF Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input You should avoid combining any of these methods EIVA MARINE SURVEY SOLUTIONS 7 10 Topcon The TopCon drivers in NaviPac supports two data formats TOPCON NP format NPOB3 NAVPOS V time 0 status sat sat2 datum lat long height height geoidal separator indicator separation hdop vdop hRMS vRMS hVel vVel 85 NMEA GGA GGA time Latitude N S Longit
16. ation 5 21 H E Gyro 3 Hig Motion sensor Remote GPS 1 E 7 Doppler log 34 Elo Dynamic positioning 4 nainii a Kongsberg LBL 8 OB Kongsberg HiPAP APOS E Kongsberg Hain Offsets X m Remote GPS 1 Offsets Y Om B E Special input 1 Offsets 7 me ED Data output 2 B 8J Data acquisition Dedi On Remote GPS 1 Offsets d Driver details B ic Geodesy Location E a Objects Deskew position aC Warm start Deskewing filer D 0 1 Latency Os Use time in telegram hh mm ss Must NaviPac use the timestamp in the NMEA telegram to establish when the position was valid NOTE Requires that the NaviPac pc is synchronized with GPS dock 12 06 2014 08 28 43 Loading set up file CAE MAN avi PacsDB aensetup D B Status Auto Manual Save Figure 9 Time selection for Remote GPS instrument Check the checkbox for the property Use time in telegram hh mm ss Page 24 of 30 8 3 ORE BATS POREG FJ NaviPac Configuration File Setup File View Options Tools Help m File header ag Instruments h Surface navigation 1 25 HO Gyro 3 ig Motion sensor E 7 Doppler lag Be Ae Dynamic positioning 5 g Kongsberg LBL H A Kongsberg HIPAPAAPOS Kongsberg Hain RB Remote GPS 1 1 VORE BATS P0REG ial input 1 eC Data output 2 E 8 Data acquisition 5 9 Offsets 4 ec Geodesy Bii Objects E T Warm start CEMA aviPac DB aensetup D B 1 0 Name Offsets X Offsets Y O
17. buffer area The process controls the navigation cycle as it with user determined frequency e Tells all threads to use new buffer area e Stores header information in the buffer e Tells the kernel to start processing using the buffer area e Waits until next cycle This gives a minimal load of the real time process and ensures an optimal time tagging of the incoming data 2 Simple timing To secure the best timing the thread should interrupt on the first character in an incoming telegram register time and read the entire telegram This gives a high load of the system and with many high frequency sensors the load would kill the OS system as Windows does not give any efficient handles to that Instead NaviPac has a smarter and much more efficient way to handle interrupts NaviPac defines an interrupt on the last character in the telegram most often lt LF gt When lt LF gt occurs on the port NaviPac gets an interrupt and registers the clock timestamp tO Then NaviPac reads the entire telegram EIVA MARINE SURVEY SOLUTIONS Based on the length of the telegram NaviPac calculates total transmission time dT as length multiplied by time per character For example on a 9600 Baud line with N81 NaviPac estimates 0 0009375 seconds per character A typical GPS telegram like GPGGA 132022 00 5408 8167 N 00900 0001 E 2 5 04 112 M 0 M 0 0 1234 lt CR gt lt LF gt with 69 characters will be transmitted in 0 0646875 seconds
18. e Kongsberg LBL Pad E H A Kongsberg HiPAP APOS ame 5 ROVINS Position 84972 l Zz Kongsberg Hain Offsets X m B Remote GPS 1 Offsets Y H ORE BATS POREG Offsets 7 lB GT E Special input 1 I O Mode m Data output 2 Driver details E e Data acquisition Location 8 29 Offsets 4 RC ee ERG NI Geodesy p a Objects aC Warm start Must NaviPac use the timestamp in the NMEA telegram to establish when the position was valid NOTE Requires that the NaviPac pc is synchronized with GPS dock 12 06 2014 08 28 43 Loading set up file C EIVA NaviPac OB Gensetup 0B Status Auto Manual Save Figure 11 Time selection for PHINS ROVINS Position instrument The driver uses the timestamp from the PHINS ROVINS Position instrument and it is thus important that the systems are in sync with the GPS clock If the PHINS ROVINS Position instrument is synchronised with the GPS clock you may select Use time in telegram hh mm ss EIVA MARINE SURVEY SOLUTIONS 8 5 Sonardyne USBL PSONUSBL FJ NaviPac Configuration File View Options Tools Help setup File CAEIVASNaviPac DBGensetup DB Edited E File header E 0 Instruments POE A Surface navigation 4 28 HO Gyro 3 igs Motion sensor E 7 Doppler log E re Dynamic positioning 7 H E Kongsberg LBL d JB Kongsberg HiPAP APOS E Kongsberg Hain A Remote GPS 1 B P ORE BATS POREG E PHINS ROYINS Position Sonardyne USBL FPSONUSBL B 2 Special
19. e instruments that are time tagged by the source eg GPS data directly into NaviPac and it is an absolute requirement that you in these cases synchronise the PC time with the GPS clock 10 Test of timing How do you test whether the timing is correct Well that is a rather good question 10 1 Checking calculated latency The first step is to validate that the calculated shown latencies are reasonable This can be monitored in the GPS Status window see the dedicated manual on GPS Status http download eiva dk online training NaviPac 20Manuals 8_ GPS 20Status pdf for detailed information Ed GPs Status Ele Options View Help Bc Name Mode Satellites HDOP RefStationld AgeOfData GeoidalHeight AntennaHeight Time GPS1GGA RIK 8 6 00 1021 0 000 0 000 37 400 122137 GPS2GGA RIK 8 611 102 0 000 0 000 37 400 122137 15 5 2014 15 51 38 Figure 13 GPS Status window illustrating age of data According to specification and tests performed by the Norwegian time group founded by Statoil EIVA MARINE SURVEY SOLUTIONS Here the AgeofData field shows either the dynamic latency in the telegram eg Ashtech GPS and Racal UKOOA or the calculated latency eg Trimble Please note that the calculated latency shows how old the navigation data is when NaviPac is using it this cannot be compared with the latency when it is transmitted from the instrument The AgeofData value might typically be up to one second higher Another t
20. est can be done by logging some data in general format in the LogData module where the incoming telegrams are displayed together with the final time tagging e R44 5 2002 01 09 14 00 49 000 GPGGA 130049 00 5408 75287 N 0918 29618 E 3 7 2 10 00037 4 M 00000 0 M 0 87 1021 R44 If time is synchronised with a GPS there should be a good correlation between the time tagging and the time in the telegram The same principle can be used for time synchronised Kongsberg HIPAP APOS instruments e R496 10 2002 01 09 14 00 49 021 PSIMSSD 130049 02 B02 A M 100 00 10 00 60 00 1 21 1 1 1 2 1 3 23 4 hh B R496 e R496 10 2002 01 09 14 00 49 010 PSIMSSB 130049 01 B02 A C H M 100 07 10 10 61 26 1 2 N hh A R496 e R496 10 2002 01 09 14 00 49 030 PSIMSSD 130049 03 B02 A S 101 00 10 00 61 00 1 21 1 1 1 2 1 3 23 4 hh C R496 10 2 Testing of time synchronisation If NaviPac is set up to synchronise the internal PC clock via interfacing of either the UTC or the ZDA telegrams it might be rather hard to check the validity of the synchronisation One method is again to check a general log file where the time in the incoming telegram should correspond to the timestamp e R505 12 2001 01 25 21 48 04 001 UTC 01 01 25 21 48 04 56 R505 Please note however that identical timing does not guarantee correct time synchronisation 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 29 of 30 Page 30 of 30 EIVA M
21. ffsets Z I O Mode Driver details UW hold time Gyro add angle Roll add angle Pitch add angle Scale Range tolerance Use stacked surface nav Use time in telegram hh mm ss Free object hold time EIVA MARINE SURVEY SOLUTIONS Edited COM40 9600 N81 E ORE BATS POREG Om Om Om on 55 pe 0 of 1 100 95 300 s Use this USBL unit for differential USBL C NOTE Requires that NaviPac and HiPAP APOS is synchronised in time 12 06 2014 8 28 43 Loading set up file CAE MAN aviPac DB sGensetup D B Stopped Ed Status Auto Manual Figure 10 Time selection for ORE BATS POREG instrument Save If the ORE BATS POREQG instrument is synchronised with the GPS clock you may select Use time in telegram hh mm ss 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 25 of 30 Page 26 of 30 EIVA MARINE SURVEY SOLUTIONS 8 4 PHINS ROVINS Position This instrument is handled via the special PHINS ROVINS Position driver as discussed in the PHINS ROVINS driver manual http download eiva dk online training NaviPac e20Manuals Appendix PhinsOut pdf Fd NaviPac Configuration File View Options Tools Help Setup File CEMA asa PacsbB BGensetup DB Edited eae File header 444 EE Instruments con Surface navigation 4 27 EA Gyro 3 i 0 H 4 Motion sensor PHINS ROVINS Position E 7 Doppler lag 41 B Q Dynamic positioning E COM41 9600 N81 E
22. ing time of reception plus latency see Section 3 Timing supported by external information about latency of data e GGA format By external clock synchronisation that is by synchronising PC time with the GPS clock see Section 4 Synchronising with external clock Please note that even though the driver allows selection of ZDA supported timing this will not work Most known installations use the time in telegram mode 7 3 Geco Prakla The Geco Prakla drivers in NaviPac support the following data formats e HINAV 0101xxvvvvvvvvvvwwWw time age latitude longitude height UKOOA info gt lt CR gt lt LF gt e GECO3 WGPOS vers no name gps week timestamp age lat long height hdop vdop uv varLat varLon varH ER fix ct ct sat ref sats used ref id Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input e Locally by registering time of reception plus latency see Section 3 Timing supported by external information about latency of data Most known installations use the latency in telegram mode 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 17 of 30 Page 18 of 30 EIVA MARINE SURVEY SOLUTIONS 7 4 NMEA The NMEA GPS drivers in NaviPac support the following data f
23. input 1 E EE D ata output 2 E 48 Data acquisition 0 79 Offsets 4 B ic Geodesy H a Objects E T Warm start Name Sonardyne USEL SPS Offsets X Offsets Y Offsets Z 1 0 Mode Driver details UW hold time Gyro add angle Roll add angle Pitch add angle Scale 1 Range tolerance 100 96 Use time in telegram hh mm ss Free object hold time 300 s Use this USEL unit for differential USEL 4 n NOTE Requires that NaviPac and HiPAP APOS is synchronised in time 12 06 2014 08 28 43 Loading set up file L EPSASN aviPacsDB aGensetup D B Stopped E Status Auto Manual Save Figure 12 Time selection for Sonardyne USBL PSONUSBL instrument If the Sonardyne USBL PSONUSBL instrument is synchronised with the GPS clock you may select Use time in telegram hh mm ss 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 27 of 30 Page 28 of 30 EIVA MARINE SURVEY SOLUTIONS 9 AITU We see more and more systems where time tagging is handled via the ATTU The EIVA time tagging unit formerly called TimeBox Please see the dedicated ATTU user manual for detailed information http download eiva dk online training Various 20Manuals AT TU 20 Manual pdf Using the ATTU you can obtain time tagging accuracy significantly better than 1 millisecond and thus guarantee that no errors are introduced into the data due to time tagging In most cases you will still interface som
24. llowing sections or via standard network time control NTP etc NaviPac supports Trimble UTC or NMEA ZDA input telegrams Please note that the PPS pulse must be interfaced on a special RING or lt DSR gt indicator see Section 4 3 PPS Indicator for further details 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 7 of 30 Page 8 of 30 EIVA MARINE SURVEY SOLUTIONS 4 1 Using Trimble UTC telegram Trimble uses a special UTC telegram UTC yy mm dd hh mm ss fix lt satellites gt lt CR gt lt LF gt The telegram is outputted approximately 500 milliseconds before the time is valid As the telegram is outputted approximately 500 milliseconds before the time is valid NaviPac requires that it be combined with PPS to get more accurate timing Va MaviPac Configuration File View Options Tools Help setup File SEIVASNAVIPACSDBSGENSETLP DB E dited m A File header E D Instruments B A Surface navigation 5 10 H S Gyro 3 ig Motion sensor E 7 Doppler lag 32 E ie Dynamic positioning 3 f COM32 9600 N81 E 7 Special input 1 P Trimble UTC time PPS B im Data output 1 ac teem On Data acquisition 0 79 Offsets 4 8 e Geodesy PPS and UTC yy mm dd hh mm ss fix E 3 Objects lt satellites gt lt CR gt lt LF gt f T Warm stark Trimble
25. lt must be larger than tMin If not use the last PPS In the current version this is hardcoded to 120 milliseconds Note This will only be functional for a 1 Hz output as all telegrams following the PPS get the same time tag The use of PPS must furthermore be enabled manually for each individual GPS instrument under the Use PPS property 6 Recommended method We are often asked what the best method is NaviPac offers a variety of methods and the user must often analyse the performance of each instrument and select a method depending on the type of job and list of equipment You must also consider whether you want to use absolute time time synchronised with the external GPS clock or not The various methods described in the above sections are listed below in order of recommendation based on general level of accuracy along with some notes as to which situations they are best suited for 1 If you want to use absolute time NaviPac should be synchronised with the GPS clock and use the timestamp in GPS telegram and USBL See Section 4 Synchronising with external clock for further details This is also the preferred solution when using ATTU for sensor time tagging 2 If you do not require absolute time with millisecond accuracy but still want to use PPS as reference PPS can be assigned to specific position input See Section 5 Assigning PPS to specific position input for further details 3 Ifthe GPS telegram includes info
26. o hh mm ss and ms 00 Potential errors If the UTC telegram is outputted much less than 500 milliseconds before its corresponding PPS telegram the time synchronisation might lose track By much less it is meant so much that the two telegrams are almost merged 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 9 of 30 Page 10 of 30 EIVA MARINE SURVEY SOLUTIONS 4 2 Using NMEA ZDA telegram A similar driver has been made to use ordinary NMEA ZDA telegrams to synchronise the PC time with the GPS clock Again this MUST be combined with PPS to get maximum accuracy Here it is assumed that the ZDA telegram is received after the corresponding PPS but with a small enough delay that it can be received clearly before the next PPS If the GPS cannot guarantee that the PPS and the ZDA match you risk faulty synchronisations In NaviPac you select ZDA time PPS as a special input on a separate dedicated COM port The PC time is then automatically synchronised with the GPS clock WE NaviPac Configuration File View Options Tools Help setup File LAEPASNHAVIPACSDBSGENSETUP DB Edited Ee File header E i Instruments aM A Surface navigation 5 12 EA X Gyro 3 Ed Motion sensor E 7 Doppler log EJ Dynamic positioning 3 COM32 9600 N31 E re Special input 1 D4 time PPS ZDA time PPS G Data acquisition 79 Offsets 4 B T Geodesy E m
27. o much This cannot be real if it continues try a forced time synchronisation under Online gt Edit Date and Time or restart NaviPac e hh mm ss Update time from hh mm ss sss to hh mm ss sss PPS signal was received successfully and the clock was adjusted
28. ormats e GGA time Latitude N S Longitude E W Quality Satellites HDOP Antenna Alt Unit Geoidal separation Unit Age Diff ID lt CR gt lt LF gt e GGK UTC Date Latitude Longitude Quality NoSat DOP Height CR LF e GLL Latitude N S Longitude E W time status mode lt CR gt lt LF gt Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing e Locally by the use of PPS see Section 5 Assigning PPS to specific position input e By external clock synchronisation that is by synchronising PC time with the GPS clock see Section 4 Synchronising with external clock You should avoid combining any of these methods 7 5 Leica The Leica drivers in NaviPac support the following data format e Binary format Sync Length ld GPS Cl source pos des Pos fail gt Datum Lat Long Height Check If operated in ASCII NMEA mode please see the information on NMEA GPS drivers in Section 7 4 NMEA Timing of positioning data can be performed using the following methods e Locally by registering time of reception plus fixed latency see Section 2 Simple timing The age is fixed and well known please contact Leica for the actual value All other methods are invalid and should be avoided EIVA MARINE SURVEY SOLUTIONS 7 6
29. osition will be extrapolated deskewed to be valid exactly when the telegram is output In that case the fixed latency value defined should be zero or close to zero 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 5 of 30 Page 6 of 30 EIVA MARINE SURVEY SOLUTIONS 3 Timing supported by external information about latency of data GPS instruments are based on a series of internally calculated data calculations before the information is sent on the port to NaviPac NaviPac can calculate this data latency by using a method in which the latency is read from the position telegram Ashtech has extended the GGA telegram when operating in RTK as they use the age field for two things e The part before the decimal point is the correction latency e The part after the decimal point is the position latency Fa NaviPac Configuration File View Options Tools Help setup File CAE MASNaviPac OB Gensetup DB H File header a Instruments j S k Surface navigation 10 7 ii B Geco Prakla GPS 1 j Ee Artemis driver 2 Use latency in telegram RTK eE eshtech GPS Fixed age Free Position input Geoidal height BE a BR CNav GPS 2 i Northing C O AB Leica GPS2 palsies Topcon GFS 4 Send command file E Leica Total 1 RvB a NONE Nm Pod E Leica GP51 Apply ITRF shift LU EI lm Ee AGA Geodimeter om amp Gyro 5 Must MaviPac read the position delay in the string
30. rmation about data latency eg Geco Prakla GPS NaviPac can use that information to compensate the timestamp See Section 3 Timing supported by external information about latency of data for further details 4 If you are not that focused on time accuracy just use the input telegram as reference for example with fixed latency See Section 2 Simple timing for further details Methods 2 and 3 can be considered equally accurate Note Do not combine methods on the same instrument this may lead to arbitrary behaviour 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 15 of 30 Page 16 of 30 EIVA MARINE SURVEY SOLUTIONS 7 GPS instruments This section lists how NaviPac can handle each set of GPS instrument types Currently NaviPac supports the following types of GPS instruments e Ashtech e C Nav e Geco Prakla e NMEA e Leica e POSMV Group e Racal UKOOA e Sea iff Skyfix e Sercel NS230 e Topcon e Trimble 4000 The following sections describe how handling of the various GPS instrument types can be done in NaviPac but we still recommend that you check with the manufacturer whether they suggest alternative handling 7 1 Ashtech The Ashtech GPS drivers in NaviPac support the following data formats e GGA time Latitude N S Longitude E W Quality Satellites HDOP Antenna Alt Unit Geoidal separation Unit Age Diff ID lt CR gt lt LF gt e GGK UTC Date Latitude
31. ude E W Quality Satellites HDOP Antenna Alt Unit Geoidal separation Unit Age Diff ID lt CR gt lt LF gt Timing of positioning data can be performed using the following methods Locally by registering time of reception plus fixed latency see Section 2 Simple timing Locally by the use of PPS see Section 5 Assigning PPS to specific position input Topcon NP format Locally by registering time of reception plus latency see Section 3 Timing supported by external information about latency of data GGA format By external clock synchronisation that is by synchronising PC time with the GPS clock see Section 4 Synchronising with external clock Please note that even though the driver allows selection of ZDA supported timing this will not work Most known installations use the time in telegram mode 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 21 of 30 Page 22 of 30 EIVA MARINE SURVEY SOLUTIONS 7 11 Trimble 4000 The Trimble 4000 drivers in NaviPac support the following data formats e GGA time Latitude N S Longitude E W Quality Satellites HDOP Antenna Alt Unit Geoidal separation Unit Age Diff ID lt CR gt lt LF gt e GGK UTC Date Latitude Longitude Quality NoSat DOP Height lt CR gt lt LF gt e ddddddd tt tt ttMdd mm mmmmmmN ddd mm mmmmmmE hhhhhh hhh pp p lt CR gt lt LF gt e 00 Thu 218 06 Aug 98 15 22 51d56 13 7620N 006 2
32. y pin amp Figure 6 Selection of PPS indicator 5 Assigning PPS to specific position input If you do not want to use the external time synchronisation you may instead select to assign the PPS to each incoming GPS data telegram NaviPac has a property for each GPS instrument Use PPS where the user can select whether time tagging must be performed based on incoming data ordinary or based on data valid flag PPS 16 Timing Principles in NaviPac docx Last update 26 6 2014 Page 13 of 30 Page 14 of 30 EIVA MARINE SURVEY SOLUTIONS F3 NaviPac Configuration File View Options Tools Help Setup File CSEIVANNAVIPAENDBNGENSETLP DB Edited m File header E Instruments E Surface navigation 5 12 eso GP53 NMEA B Geco Prakla GPS 1 Offsets X Om Ee Artemis driver 2 Offsets Y om B Ashtech GPS1 ERREUR lon 2 Ej Free Position input P GPS3 NMEA Ee AGA Geodimeter Driver details H S Gyro 3 Apply datum shift oO Hig Motion sensor Use FPS ae Doppler log T x i Dynamic positioning 3 ee eed Hg Special input 1 Fixed age 0 12s i e Data output 1 Geoidal height Om amp Data acquisition a EY E 3 a Offsets 4 If you have configured the GPS port so it receives a PPS cs de Geodesy together with the data string then check this to make p Objects MaviPac use the pulse for time tagging E O Note that this will not synchronize the PC dock this requires a Warm start special
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