Incoherence between .pos points and recorded position (reachview App)

Reach Module / M+ / M2 RTK / PPK configuration
1

Hi,

I’m trying to understand why there is are significant differences between a recorded point (ReachView app) and the postprocess point (.pos) during the same time windows. The pattern is shown here for one point, but they more or less all show the same behavior.

The recorder point
If I look at one point which is recorded with Reachview app, between 6:48:31 and 6:48:33

p.survey = as.vector(dt.survey[5,c("Name", "Averaging.start", "Averaging.end", "Latitude", "Longitude", "Easting.RMS", "Northing.RMS")])
> p.survey
Name: 5
Averaging.start: "2022-08-05 06:48:31 UTC"
Averaging.end:  "2022-08-05 06:48:33 UTC"
Latitude: 37.42344774
Longitude: 23.48991202
Easting.RMS: 0.012
Northing.RMS: 0.01

The postprocess individual track
Here are the points out of the postprocessed .pos file, between Averaging.start and Averaging.End

subset(dt.tmp, select=c(t, lat, lon, sdn, sde))
                        t         lat         lon    sdn   sde
10966 2022-08-05 06:48:31 37.42344338 23.48992526 0.0032 0.003
10967 2022-08-05 06:48:31 37.42344349 23.48992580 0.0032 0.003
10968 2022-08-05 06:48:31 37.42344371 23.48992571 0.0032 0.003
10969 2022-08-05 06:48:32 37.42344410 23.48992543 0.0032 0.003
10970 2022-08-05 06:48:32 37.42344497 23.48992506 0.0032 0.003
10971 2022-08-05 06:48:32 37.42344592 23.48992477 0.0032 0.003
10972 2022-08-05 06:48:32 37.42344644 23.48992497 0.0032 0.003
10973 2022-08-05 06:48:32 37.42344667 23.48992516 0.0032 0.003
10974 2022-08-05 06:48:33 37.42344700 23.48992518 0.0032 0.003

Question
All the precision look pretty good to me. We were steady during the measure with the pole.

Nonetheless, there is a big driget in the recorded positions (10-20cm):

distHaversine(c(mean(dt.tmp$lon), mean(dt.tmp$lat)), subset(dt.tmp, select=c(lon, lat)))
[1] 0.1891072632 0.1827543713 0.1568384302 0.1090583973 0.0212944573 0.1032425597 0.1545916923
[8] 0.1774442340 0.2139806176

And those track points are pretty off the recorded point.

Could you help me understand where I got lost?

Thanks for your help,
Alex

3

Hi Alexandre,

Sorry for the silence here!

ReachView 3 uses UTC, and .pos files show GPST. GPST is 18 seconds ahead of UTC. Do the coordinates match if these leap seconds are taken into account?

5

Hello Kseniia,

You nailed it !!!

That would have been a hard one to discover by myself.

From Greece, where we use your equipment to do exciting stuff, we thank you a thousand times :slight_smile:

Alex

6

Glad that it helped! Exciting stuff sounds intriguing, so I’d love to read more about it if you’re ready to share some details here :slightly_smiling_face:

7

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