AORPLS
May 28, 2025, 11:39pm
1
Carlson talks about
To do GNSS averaging. Any idea if this is a nmea message or just proprietary?
rftop
May 29, 2025, 4:13am
2
It’s an Open Issue in the Repo for the “older” FW.
opened 03:44PM - 21 Sep 22 UTC
File this in the Pipe Dreams drawer. :)
### Subject of the issue
Provide GNS… S vectors (from base to rover). A number of high-end survey-grade GNSS receivers provide GNSS vectors in addition to the coordinates of a recorded point, and corresponding data collectors collect this data. There appear to be a number of proprietary APIs and data formats between commercial data collectors and GNSS receivers to request and gather this data.
GNSS vectors can be used for high-precision processing of the survey data. An individual vector represents the line between the RTK base and the rover, and it includes error information. This data can be used, for example, in a least squares adjustment to apply statistical tests to the data and perform precision adjustments. Longer vectors (perhaps when using network bases) can be given less weight than shorter vectors. Vectors with better DOP, less noise, smaller sdevs, for example, can be given more weight than those with less-favorable characteristics.
The NGS proposed a non-proprietary format for this data:
https://geodesy.noaa.gov/data/formats/GVX/index.shtml
At least one data collector can use this vector data in real time to perform advanced averaging of the GNSS observations to determine the mark coordinates. Mark Silver says this functionality has been in SurvCE since 2013. The opening moments of his video describe its usefulness.
https://www.youtube.com/watch?v=umiRftGkd3A
I'm really not sure how the (proprietary?) interfaces between the GNSS receiver and the data collectors work; does the GNSS receiver continually transmit the vectors intermixed with the NMEA stream and the data collector grabs a vector (along with the NMEA position report) when the surveyor uses the data collector to measure a point?
There is a F9P message that provides base-rover vectors, apparently this is used when the base and rover are both fixed to a moving platform (drone) and intended to be used for heading determination. Is this the same vector that the NGA and Mark Silver are talking about?
I'm not even sure what I'm asking the RTK Firmware to do.
Well, thanks for reading this!
### Expected behavior
System to provide GNSS vectors for processing by adjustment software.
AORPLS:
GNSS averaging
This one may shed some lights. https://www.youtube.com/watch?v=duSP5xYJw6w
rftop
May 29, 2025, 2:11pm
4
@dilshana , that’s a great video. Thanks for sharing it.
@AORPLS , it’s “plausible” that the vectors are stored in the RAW file. Can you save the RTCM file and point Carlson to it?
It’s very possible that you might need to convert to RINEX at a minimum, if the RTCM doesn’t work for Carlson.
I noticed that the Mosiac x5 supports gvx which is the open source vector protocol unfortunately it appears Carlson turns off looking for these on generic nmea and they aren’t super poised to support outside devices they even stopped supporting emlid.
I am going to try my bosses brx6+ and see what it does compared to the postcard.
Been trying to test mosiac facet but it won’t go below about a 4 pdop and makes no sense.
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