Software configuration Precise antenna positioning. Software configuration Precise antenna positioning

Transcription

1 Precise antenna positioning 43 Precise antenna positioning 44 36

2 Precise antenna positioning 44 Precise antenna positioning 44 37

3 Precise antenna positioning The US National Oceanic and Atmospheric Administration provides a similar service 45 Precise antenna positioning 45 38

4 Precise antenna positioning 45 Precise antenna positioning 45 39

5 From: opus Software Sent: Tuesday, configuration 20 September :45 To: Marais, Louis Subject: Precise antenna positioning OPUS solution : TRVL O OP FILE: TRVL O OP NOTE: Antenna offsets supplied by the user were <=0. Coordinates 1008 returned will be for the antenna reference point (ARP) NGS OPUS SOLUTION REPORT ======================== All computed coordinate accuracies are listed as peak-to-peak values. For additional information: USER: louis.marais@measurement.gov.au DATE: September 20, 2016 RINEX FILE: trvl o TIME: 03:44:24 UTC SOFTWARE: page master52.pl START: 2016/08/12 00:00:00 EPHEMERIS: igs19095.eph [precise] STOP: 2016/08/13 00:00:00 NAV FILE: brdc n OBS USED: / : 95% ANT NAME: JNSMARANT_GGD NONE # FIXED AMB: 234 / 268 : 87% ARP HEIGHT: OVERALL RMS: 0.016(m) REF FRAME: IGS08 (EPOCH: ) X: (m) 0.005(m) Y: (m) 0.008(m) Z: (m) 0.009(m) LAT: (m) E LON: (m) W LON: (m) EL HGT: (m) 0.012(m) UTM COORDINATES UTM (Zone 56 Set the position for the travelling receiver To use cggtts results antenna position must be set A utility called setcoords is provided 47 40

6 Set the position for the travelling receiver To use cggtts results antenna position must be set A utility called setcoords is provided 47 Set the position for the travelling receiver To use cggtts results antenna position must be set A utility called setcoords is provided 47 41

7 Set the position for the travelling receiver To use cggtts results antenna position must be set A utility called setcoords is provided 47 Set the position for the travelling receiver 47 42

8 Set the position for the travelling receiver 47 Set the position for the travelling receiver 47 43

9 Set the position for the travelling receiver 47 Set the position for the travelling receiver 47 44

10 Set the position for the travelling receiver 47 Set the position for the travelling receiver 47 45

11 Set the cable delays for the travelling receiver The cable delays also need to be set for Antenna cable (if using your own) Reference 1PPS cable We provide the setdelays utility to simplify this 48 Set the cable delays for the travelling receiver 48 46

12 Set the cable delays for the travelling receiver 48 Set the cable delays for the travelling receiver 48 47

13 Set the cable delays for the travelling receiver 48 Set the cable delays for the travelling receiver 48 48

14 Set the cable delays for the travelling receiver 48 Set the cable delays for the travelling receiver 48 49

15 Set the cable delays for the travelling receiver 48 Backups of the configuration file 49 50

16 Uncertainty of receiver delay Example Working through an example will aid understanding We treat the Antenna Delay, GPS Receiver Internal Delay, GPS Receiver 1PPS Delay and Counter Differential Channel Error as a single value which we call Receiver Delay. This reduces the uncertainty significantly 50 Antenna Delay Antenna Cable ns ±0.6 ns Delay GPS Rx 1PPS GPS Receiver Internal Delay Cs Clock 1PPS 10MHz 23.7 ns ±0.6 ns Cs Clock 1PPS Delay GPS Receiver 1PPS Delay ns ±1.3 ns 1 Ext Ref 2 Timer / Counter Uncertainty of receiver delay Example So we have the following values (standard uncertainties): Antenna cable: ns ±0.6 ns Reference 1PPS cable delay: 23.7 ns ±0.6 ns Receiver delay: ns ±1.3 ns We need to determine the type B uncertainty to assign to our time transfer system Use standard GUM technique to do the calculation: 51 3 i 1 u c u i ns ns 51

17 Uncertainty of receiver delay Example For the previous calculation, we only measured the reference 1PPS delay If both the antenna cable and the reference 1PPS delay was measured with the same counter there are correlations, and we need to add those measurements together Assume perfect correlation, correlation coefficient = 1 The calculation then becomes: 3 i 1 u c u 2 i ns ns 52 Uncertainty of receiver delay Measuring cable delays How do we measure these delays? Two examples: Using MicroSemi/Agilent/HP 5313xA Using Stanford Research Systems SR

18 Uncertainty of receiver delay Measuring cable delays Reference 10 MHz 1 PPS Time Interval Counter EXT REF CH1 CH2 Channel 1 settings: Trigger rising slope Level 0.5 peak voltage DC coupling Input : High Impedance Cable to be measured Channel 2 settings: Trigger rising slope Level 0.5 peak voltage DC coupling Input : 50 Ω 53 Uncertainty of receiver delay Measuring cable delays: model 53131A 53

19 Uncertainty of receiver delay Measuring cable delays: model 53131A CHANNEL 1 CHANNEL 2 54 Image source: Uncertainty of receiver delay Measuring cable delays: model 53131A 10 MHz CHANNEL 1 CHANNEL 2 1PPS Channel 1 settings: Trigger rising slope Level 0.5 peak voltage DC coupling Input : High Impedance Channel 2 settings: Trigger rising slope Level 0.5 peak voltage DC coupling Input : 50 Ω Uncertainty is ~ 2 ns, most contributed by Differential Channel Error 54 Image source: 54

20 Uncertainty of receiver delay Measuring cable delays: SR620 Uncertainty of receiver delay Measuring cable delays: SR MHz EXT A B REF OUT 1PPS 55 Image source: 55

21 Uncertainty of receiver delay Measuring cable delays: SR MHz EXT A B REF OUT Channel A settings: Trigger rising 1PPSslope Level 0.5 peak voltage DC coupling Input : High Impedance Channel B settings: Trigger rising slope Level 0.5 peak voltage DC coupling Input : 50 Ω Uncertainty is ~ 1.2 ns, most contributed by Differential Channel Error 55 Image source: Uncertainty of receiver delay Measuring cable delays: SR MHz EXT A B REF OUT Channel B settings: Trigger rising slope Level 0.5 peak voltage DC coupling Input : 50 Ω Uncertainty is ~ 1.2 ns, most contributed by Differential Channel Error 56 Image source: 56

22 Time Transfer Systems NMIA has been making systems for about 20 years Initial versions used industrial computers and HP counters Later versions used single board computers and counter cards Version with rubidium oscillator offered Latest version (under development) uses single board computer and FPGA based counter Contains 3 GNSS receivers (GPS, GLONASS, Beidou) Version with GPSDO offered 57 Time Transfer Systems: Version

23 Time Transfer Systems: Version 1 58 Time Transfer Systems: Version

24 Time Transfer Systems: Version 2 Computer Counter card NTP card GPS card (below) Rubidium oscillator 59 Time Transfer Systems: Version

25 Time Transfer Systems: Version 3 (being developed) GPS receiver GLONASSS receiver Computer Beidou receiver GPSDO FPGA counter 60 Time Transfer Systems: Version 3 (assembled) RF Splitter 60 60

26 Open Traceable Time Platform With assistance from APMP a inexpensive version of our Time Transfer System is being developed Goal is for it to cost less than $2000 It uses a single frequency GPS receiver Several receivers were evaluated Trimble SMT360 NVS08C Easy to customise: Hardware and software openly available github.com/openttp 61 Open Traceable Time Platform APMP partners in this development NPLI, India NML-SIRIM, Malaysia NIMT, Thailand Time frame is short, about 18 months Hope to deliver hardware to partners by November Further software development Customisation 62 61

27 Open Traceable Time Platform 63 Open Traceable Time Platform

28 Open Traceable Time Platform 63 Open Traceable Time Platform

29 Open Traceable Time Platform 63 Open Traceable Time Platform

30 Open Traceable Time Platform github.com/openttp 64 Open Traceable Time Platform github.com/openttp 64 65

31 Open Traceable Time Platform github.com/openttp 64 Open Traceable Time Platform github.com/openttp 64 66

32 Open Traceable Time Platform github.com/openttp 64 My OPENTTP Open Traceable Time development Platform system, built on a piece of plywood Computer GPS receiver FPGA counter GPSDO RF Splitter 65 67

33 Open Traceable Time Platform 66 Open Traceable Time Platform 66 68

34 Questions Department of Industry, Innovation and Science National Measurement Institute 36 Bradfield Rd PO Box 264 West Lindfield Lindfield NSW 2070 NSW 2070 Telephone louis.marais@measurement.gov.au 69