GPS post-processing is not very well

Reach Module / Reach RS+ / RS2 RTK / Post-processing configuration
#1

Hi, I did a experiment using 2 Reach RS+. One for base, and one for rover.

The date (latitude and longitude) of base is very accurate after I putted it on the ground about 30 min. And base also connected to Virtual Reference Stations in my country.

And then I walked about 500 meters away from base with the rover and stopped for about 30 minutes.

The question is when I do GPS post-processing following the tutorial:
https://docs.emlid.com/reach/common/tutorials/gps-post-processing/
the location of rover offsets several meters.

The result is not very well.

Can somebody tell me what mistakes did i make?

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For example: at 2018/04/02 08:34:34.600 the rover’s location is (24.180040110, 120.708935849), but the real location is (24.180172, 120.708962).

The following is compression file of base and rover:


THX

#2

If you open up your rover’s position file with a text editor and look around line 22. Does the reference position contain the correct coordinate for your base location?

1 Like
#3

Just as @bide said, please make sure the base position you use when processing is right. This is the most probable cause of the shift.

#4

THX for reply~~~

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I saw the rover’s position file.
The reference position is ( 24.178301935 120.702315343 ). It is not right location of base.
My base location is about ( 24.178270316 120.702295872 ).
The following is base solution (.LLH).

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You can see the latitudes and longitudes are very close to base location.

So, why the reference position is wrong after I doing GPS post-processing?

THX~~

#5
  1. Please try the newest RTKLIB build from our post-processing tutorial.
  2. Please share how you enter the base position into RTKPOST
#6

THX for reply~~

I used the newest RTKLIB build
And the following are steps I processing these data.
I follow the tutorials basically.

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And in the last step, I choose two kinds of buttons. “Average of Single Position” and “RINEX Header Position”. But both of them are all wrong (reference position of result is wrong).

I am gassing if the position of base is unstable in the beginning, so the result is wrong after calculating.

#7

Hello!
As Ì understand it,
“Average of singe positions” should be an average over all the positions in the base station log file (using whatever correction the base is receiving - often none).
“RINEX Header Position” is the the last known position - again using any available correction to the base - or none if none is available).

If you know the position of the base, you should enter it manually using “Lat/Lon/Height” or “X/Y/Z-ECEF”.

Best regards,
Lars

#8

THX for reply~
I think because the error of “Average of singe positions” is too much. And the last known position of “RINEX Header Position” is a wrong position.

I will try “Lat/Lon/Height” by choosing a set of good numbers in .pos file.

THX again~~~

#9

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