From 7f997646f0c9908a31a233068ebc16029f53cb92 Mon Sep 17 00:00:00 2001 From: "Gary E. Miller" Date: Mon, 20 May 2019 16:23:33 -0700 Subject: ppp-howto: Add Trimble RTX as working with gpsrinex. --- www/ppp-howto.adoc | 70 +++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 51 insertions(+), 19 deletions(-) (limited to 'www') diff --git a/www/ppp-howto.adoc b/www/ppp-howto.adoc index 5018e377..1a2c45a5 100644 --- a/www/ppp-howto.adoc +++ b/www/ppp-howto.adoc @@ -9,18 +9,20 @@ V0.99, Nov 2018 This document is a guide getting high accuracy static positions from your GPS using Precise Point Positioning (PPP). The rare few that have a GPS that output raw measurement data for L1 and L2 can achieve absolute -accuracy of around 3 cm. The lucky owners of an L1 GPS that outputs raw -measurements can get about 0.5 m. The majority will only be able to get -somewhat better than 1.5 m using simple averaging. +accuracy of around 3 cm. The u-blox ZED-F9P and ZED-F9T can be better +than 1 cm. The lucky owners of an L1 GPS that outputs raw measurements +can get about 0.5 m. The majority will only be able to get somewhat +better than 1.5 m using simple averaging. Patience is required. For best results 6 to 24 hours of data is required. Post processing time may double that. -This document is not about getting high precision dynamic positions -from your GPS. That requires Real Time Kinematic (RTK) which will -not be discussed here. RTK users will still want to read this document. -The RTK Best practice is to determine the position of the base using -PPP before sending the RTK data from the base to its rovers. +This document is not about getting high precision dynamic positions from +your GPS. This is about static Post Processed Positions (PPP). High +precision dynamic positions requires Real Time Kinematic (RTK) which +will not be discussed here. RTK users will still want to read this +document. The RTK Best practice is to determine the position of the +base using PPP before sending the RTK data from the base to its rovers. == Requirements == @@ -40,11 +42,12 @@ measurement data that GPS understands. Currently that limits you to a Javad GPS that support the GREIS language, or a u-blox GPS that support the UBX-RXM-RAWX messages. -u-blox GPS known to support UBX-RXM-RAW are: -M8T and -M8F. +u-blox GPS known to support UBX-RXM-RAW are: -M8T,-M8F, ZED-F9P and +ZED-F9T. For advanced PPP (3 cm) you will need a GPS that outputs L1 and L2 raw measurement data that GPS understands. Currently that limits you to a -Javad GPS that support the GREIS language. +Javad GPS that support the GREIS language or the u-blox 9 series. Finally, patience is required. @@ -183,6 +186,11 @@ There is one online service that is free to all (requires registration), accepts L1 only raw data, and accepts RINEX 3 files: Natural Resoruces Canada (NRCAN). Their tool is at https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php +Trimble has a free to all (requires registration) service that requires +L1 and L2 observations in RINEX 3. + Their +tool is at: https://trimblertx.com/Home.aspx + == PPP Configuration == Before you can collect raw data from you GPS, you must configure it to @@ -214,7 +222,7 @@ $ ubxtool -d NMEA $ ubxtool -e BINARY ................................... -Disable all constellations, except GPS (and QZSS): +To start simple, disable all constellations, except GPS (and QZSS): ................................... $ ubxtool -d GLONASS @@ -224,8 +232,9 @@ $ ubxtool -d SBAS $ ubxtool -e GPS ................................... -Verify that only GPS and QZSS are enabled. Otherwise the u-blox will -not output raw measurement data. +Verify that only GPS and QZSS are enabled. Otherwise the u-blox 8 will +not output raw measurement data. You may enable the other constellations +with a u-blox 9, but support for non-GPS in PPP services is limited. ................................... $ ubxtool -p GNSS @@ -325,8 +334,9 @@ data from the GPS: Configuration complete. Collect 24 hours of samples at 30 second intervals, save the raw data as RINEX 3 format in the file _today.obs_. -Collecting data at a rate faster than 30 second intervals will degrade -your results. Start the long process: +Collecting data at a rate faster than 30 second intervals may degrade +your results. Trimble will average data to 10 second intervals if +the data rate is faster than 10 seconds. Start the long process: ................................... $ gpsrinex -i 30 -n 86400 -f today.obs @@ -342,6 +352,18 @@ ultimate question of life, the universe, and everything. == Post Process the Raw Data == +More waiting. Before you can post process your data, the PPP service +must be ready for it. Depending on the service it can take from 10 to +60 minutes before you can upload your new data. For best results you +should wait 2 weeks. + +The following two services are known to work with _gpsrinex_. CSRS-PPP +will accept L1 only data, trimble RTX requires L1 and L2 data. Try +both, with the same data set, if you can. That will show you that their +sigma's are "optimistic". + +=== CSRS-PPP === + After _gpsrinex_ is complete, you need to login to CSRS-PPP and upload the RINEX 3 file. After login you will be taken to the upload page. Enter your email address, so the results can be emailed to you. @@ -353,7 +375,13 @@ push "Submit to PPP". All done, except for more waiting. You will receive an email from NRCAN maybe within minutes, maybe up to 36 hours later, with a link to a file called: full_output.zip. Unzip, and Voila! Inside is a PDF file with -your precise position. +your precise position, and other goodies. + +=== Trimble RTX === + +Before uploading today.obs to Trimble you will need to change the _.obs_ +extention to _.YYo_, where YY is the 2-digit year. Then proceed as +above with CSRS-PPP. == References == @@ -366,14 +394,18 @@ https://confluence.qps.nl/qinsy/en/world-geodetic-system-1984-wgs84-29855173.htm Information on vertical datums: https://www.nrcan.gc.ca/earth-sciences/geomatics/geodetic-reference-systems/9054#_Toc372901506 -One service known to work with obsrinex output is CSRS-PPP at NRCAN: +One service known to work with gpsrinex output is CSRS-PPP at NRCAN: https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php +Another service known to work with gpsrinex output is Trimble RTX +from Trimble. They require dual frequency (L1 and L2) raw data: +https://trimblertx.com/Home.aspx + OPUS requires L1/L2 frequency observation files, and has limited geographic coverage: https://www.ngs.noaa.gov/OPUS/ -The curious can find the RINEX 3.03 format described here: -ftp://igs.org/pub/data/format/rinex303_update1.pdf +The curious can find the RINEX 3.04 format described here: +ftp://ftp.igs.org/pub/data/format/rinex304.pdf // vim: set syntax=asciidoc: -- cgit v1.2.1