GPS post-processing is not very well

Reach Module / M+ / M2 RTK / PPK 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:

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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%E6%9C%AA%E5%91%BD%E5%90%8D648Ă—541 32.1 KB

%E6%9C%AA%E5%91%BD%E5%90%8D2
%E6%9C%AA%E5%91%BD%E5%90%8D21920Ă—1013 156 KB

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
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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.

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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).

002
002.png1358Ă—646 68.9 KB

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~~

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  1. Please try the newest RTKLIB build from our post-processing tutorial.
  2. Please share how you enter the base position into RTKPOST
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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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0003.png624Ă—493 79.3 KB

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0004.png601Ă—444 69.9 KB

0005
0005.png721Ă—451 49 KB

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 ĂŚ 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

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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~~~

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