RS2 post processing RtkPost

I recorded some points for a short time (1 ') to prove the site visit and test. I was surprised because when playing on RTK Post to test, the points were fixed in the first attempt. I found it a little strange. The points had few observations and remained, showing a large discrepancy with the fixed points in RTK mode. I wonder if this is normal. What are the ideal settings of Rtk Post, and what is the procedure for analyzing the quality of processing.

Att
Mauricio from Brazil

Hi Mauricio,

Usually, default RTKLIB settings work fine in most conditions.

Would you mind sharing the raw data on this test, too?

Hi Tatiana,

Follows survey files for analysis.

Hi Mauricio,

Thanks, we’ll check the data and write back.

Could you please clarify how you specified the base position in RTKPOST before processing?

Good morning Tatiana,

How are you?

I entered the position in the “Positions” - »Base Station tab;
So I entered the coordinates.
I did some processing with DMS coordinates and other DEG to test if there would be a difference.

Hi Mauricio,

May I also ask you to clarify what was the baseline and environmental conditions during your tests?

Hi Tatiana,

The base was in a good, high place, with a clear horizon.
The environmental conditions were also good. Clean weather, no rain, no winds, no clouds … sunny day with a temperature in the range of 27ºC.

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I tried to process the points in the TBC (Trimble Business Center), but I couldn’t.
Trace sessions are failed.

Another survey managed to process it right.

Good morning Tatiana,

All right?

I will send here some files of my equipment to check if everything is fine.

Hi Mauricio,

I’ve processed the data you shared. You can see my comments below.

I’ve got mostly float solution after post-processing all the data. It can be caused by the satellite signals’ quality obtained by the rover.

The plots below show the comparison between satellite signals obtained by the base and by the rover.

  • Rover observes only 4 satellites with SNR = 45 on L1 and 1 satellite on L2. To calculate the position, the rover requires at least 4 satellites, but the more satellite signals with high SNR rover can track the better solution will be.

  • The base, in turn, observes more than 10 satellites with SNR = 45. This fact shows that the base has been placed correctly and the working conditions are good.

May I ask you about the working conditions? This information will allow seeing a situation in more detail.

It is quite strange that the results in RTK and PPK are significantly different and I need more details to investigate the unit’s behavior. May I ask you to share the .LLH file? It will help me to compare the results obtained in RTK and PPK modes and to look into the issue more thoroughly.

I’ll check your new set of data and come back with results.

hello Anastassia

I do not own the LLH for this survey.
I started recording it after those doubts.

Strange, because in the field, the receiver accuses many satellites, on average 30 in not too bad situations.
And in post-processing it drops to 4 or 5, it’s strange.

Another thing.
I noticed that as I move away from the base, in the APP ReachView the base varies the number of satellites, takes 30, and drops to 7, then goes to 30 again, and stays in this come and go.

Hello everyone, i’ve been following this post for a while to see the results of the tests.
About the satellites available in the post-processing i’ve noticed that the use of the GLONASS constelation makes the number of used satellites go down for no aparent reason for the moment.
I’ve been notified by more than one people that using GLONASS in post-processing makes the solution worse and after removing the GLONASS satellites makes the result match with a RTK Point with milimetric precision.
Edit: All the tests where made in Brazil, parallel 22 south.

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Hello Adriano,

I realized that too.
Glonass is “spoiling” the quality of the post-processed stitch.
Problem is: How do you know if the point is really reliable?
See some traces of 1 hour in the woods, I couldn’t fix it in the RTK, I have no way of knowing if the result is reliable.
Process on RTKPost and TBC, both result in very different values.
So, the post-processed is being a “kick”.

In the field, look at your PDOP values in the Survey tab in Reachview. Anything above 2 can be hard to trust. It should preferably be below 1.6.

On top of that, look into how many sats are above 40-45 dbhz (SNR).

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Hi Mauricio,

Sorry it took so long to get back to you! It seems that these logs are no longer available for download. May I ask you to upload them again so that I can check and try to post-process them myself?

Same issues with GLONASS for almost the last year. I don’t understand the cause unless their technology is becoming insufficient. More satellites seem to be going up for other constellations so maybe they just aren’t fitting anymore. My experience is that they have had high SnR’s and allot of cycle slips.

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