Meaning of residual values in post processed results

Reach Module / M+ / M2 RTK / PPK configuration
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This is a result of a static post-processed GPS data:

% (x/y/z-ecef=WGS84,Q=1:fix,2:float,3:sbas,4:dgps,5:single,6:ppp,ns=# of satellites)
% GPST x-ecef(m) y-ecef(m) z-ecef(m) Q ns sdx(m) sdy(m) sdz(m) sdxy(m) sdyz(m) sdzx(m) age(s) ratio
2020/01/01 00:00:00.000 665805.6635 -5508490.1762 3134878.2600 1 5 0.0003 0.0006 0.0004 -0.0002 -0.0004 0.0001 60.00 8.7

I know I read somewhere here about another similar question but could no longer find that thread. The sdx,sdy,sdz,sdxy,sdyz,sdzx seems too small to really mean anything. GPS accuracies even for static observations are in the several mm. Which begs the question how can you get deviations in the sub mm values?

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Hi @jjb,

What the version of the RTKLib you use? Could you please share the .pos file with me? You can send it on support@emlid.com if it contains some sensitive information.

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Hi Svetlana
Please see attached POS file. Nothing sensitive about it. I was using it to practice on RTKLib processing.
xcty0010.pos (796 Bytes)

5

Hi
Any feedback? Thanks.

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Hi Juan,

Sorry it took so long to get back to you!

Standard deviation is the square root of the variance. The variance is the average of the squared differences from the Mean. In RTKLib, the Mean is the average of all the calculated solutions.

So, you post-processed the data in the Static mode. This means the Mean and the solution are basically the same. That’s why standard deviations values are in several millimeters.

Would you mind post-processing the data in the Kinematic mode and share the .pos file so that we can check the standard deviations in that case?

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