How does the RS2+ use SBAS corrections

[chris.martin]

This question was asked here: Standalone surveying with rs2+, but the answers largely diverted into asking why you would want it, instead of whether it was used. And now that it is >100 days old, I cannot add to that topic.

I have been running a variety of tests with my Reach RS2+ unit, and although SBAS satellites are reported in the app, I have never seen the GGA NMEA string report a quality of 2 (DGPS/SBAS/etc). The tests in question were run with the Reach set up to output NMEA over serial to a separate logger, with all constellations enabled and both the GGA and GSA strings enabled. The system was left running for approximately 1 hour.

I can see 3 options -

1. The RS2+ tracks the SBAS satellites, but doesn’t use them
2. The RS2+ tracks the SBAS satellites and uses them as part of the solution, but doesn’t report it in the GGA string.
3. The RS2+ tracks the SBAS satellites but only uses them if it improves the solution, and in my test perhaps it never made an improvement.

Can anyone clarify which of these options (or perhaps some other option I haven’t considered) is true?

Again, I’m not interested in whether I should or should not be using SBAS in a given survey design, just wanting to understand what the RS2+ is doing.

[olesia.riman]

Hi Chris,

Your second point is correct.

Multi-band Reach receivers track SBAS corrections and use them as part of the solution, but we don’t write them as DGPS in GGA string.

Just in case other users encounter this thread, I wanted to add that SBAS accuracy is 1m CEP and greatly depends on place. If you need higher accuracy, you would need to use RTK or PPK.

[chris.martin]

Thank you. Is there any way to tell when a solution is using SBAS corrections? Either in another NMEA string or in the log files?

I tried searching through the GPGSV strings, but was unable to find reference to either of the SBAS satellites shown in the app during collection (in this case 131 and 133)

[olesia.riman]

Chris,

In the NMEA GGA message, you can see only the number of satellites, not which ones are used in the solution. In the raw data, you should see which SBAS satellites are used; they are numbered without any letters. In the example below, SBAS satellites are 123, 127, 128, and 136:

[chris.martin]

Thanks