Different RTK & PPK results

I am getting different results from the RTK and PPK. I already checked the base coordinates,HI,AH settings for the RTK and PPK and they are both the same. I tried to PP because I was looking for close results to a certain float point. When I PP the 2 observation log files, I got different results for the same timestamp.
What am I doing wrong? Antenna height of base? Pole height of rover?!

The yellow highlighted values are from the RTK csv file. The blue highlighted values are from the PPK results.

Another date with different positions.

I have to ask, have your checked your base and rover antenna-heights?
Let’s get that basic question out of the way first :smiley:

yes, double checked too. the 2nd image shows a discrepancy that is not attributable to HI or AP errors. almost 80m in difference. the sd on the other hand is quite large.
I was under the impression that RTK results can be post processed from the log files and you would get approximately the same results right? Or am I wrong in this?

How is the data post processed ? What software, what settings? Same base correction?

I used rtklib QT version set to kinematic results using all satellites same as was set in the based corrections during the rtk survey.

what ambiguity setting should I use for kinematic mode? continuous or fix and hold?

If your baseline isnt too long (under 50-60 km for rs2) and your SNR is good in general, I would recommend Continous for the must trustworthy results.

Hi Juan,

Please check the solution status in the 6th column of *.LLH file. The numbers correspond to the statuses this way:

  • 1 = Fix

  • 2 = Float

  • 5 = Single

In the first case, you have the float solution. It’s submeter accurate. If you get float, the receiver likely has a poor sky view, or there are obstacles like buildings, trees, or cars around.

In the second case, you have a single solution. It’s only a few meters accurate. The single solution can appear when you process the base and rover logs that don’t overlap. Please, check the time when the logs were collected.

To get the centimeter-accurate result, you need to get the Fix after post-processing. Please try to provide your receiver with a clear sky view 30 degrees above the horizon and make sure that there are no obstacles around.


Hi, I checked the LLH file and from the time stamp, I see that Fix status sometimes have #2 (float) returns. Is that possible?

Hi Juan,

Yes, you can get fix in RTK and only float in PPK with the same data. The result depends on PPK settings. You can explore our GPS post-processing guide to check the settings that we usually recommend for post-processing.

You can change PPK settings according to your data quality. Please check the Satellite Visibility tab in RTKPlot. If there are many gaps or SNR fluctuations, there’s likely not enough data to calculate a Fix. So, you can set a lower elevation mask to take more satellites into account. In another case, if there are many signals with low SNR or cycle-slips, you may increase the SNR mask to exclude noisy signals influence.

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