RTK-RTPK discrepancy

[John Thompson]

I have a 4-foot discrepancy between RTK and RTPK coordinates that I'm having trouble understanding. I sent project Scott White to support (SN229). I was about a mile from my base, but down in a valley and at the edge of cell coverage. Skies were completely unobstructed. I had no communication from the base, so I collected three points then went back to the base, connected to it with Bluetooth, downloaded the base file without stopping the base, and post-processed each of the three points. While at the base, I noticed that I still didn't have RTK so I stopped and restarted RTN. RTK was fixed so I went back to the same three points and observed them again. This time I got RTK Fixed and RTPK shots that agree closely with each other, but have a consistent 4-ft offset from the first three RTPK points. Same distance and direction.

The first three shots (no RTK) were 1204 (163 RTPK epochs), 1205 (395 RTPK epochs), and 1206 (262 RTPK epochs).

The shots with RTK and RTPK were 1227 (28 RTPK epochs, same point as 1204), 1226 (61 RTPK epochs, close to 1205), and 1224 (123 RTPK epochs, same point as 1206.)

Why do the second set of RTPK coordinates match the RTK, but the first set of RTPK coordinates don't even though the first set have longer occupation times? The standalone coordinates of the first three shots are closer to the RTK coordinates than the RTPK coordinates. This looks like the difference between WGS84 and NAD83.

 

[Ron Cloninger]

Could the base had been using an autonomous location for the first shots

 

[John Thompson]

I wondered that too. I had used an autonomous base the day before, but DPOSed it and used the CORS position for the base on the day I took those shots. The CORS coordinate was about 1 foot horizontally from the autonomous base the day before. I did have RTK shots on the same point from both days that check well.

 

[Matthew D. Sibole]

I wondered that too. I had used an autonomous base the day before, but DPOSed it and used the CORS position for the base on the day I took those shots. The CORS coordinate was about 1 foot horizontally from the autonomous base the day before. I did have RTK shots on the same point from both days that check well.

Can you upload the project archive to a drop box and post a link here so I can look at it?

 

[John Thompson]

Scott White-211109 18_31_11.zip

Shared with Dropbox

www.dropbox.com

Here you go. Thanks for looking at it. This is the first time I've ever downloaded the base file without stopping the base and individually post-processed points. I'm hoping it's operator error.

 

[Matthew D. Sibole]

@Alexey Razumovsky I reprocessed the the 3 points (1204, 1205 and 1206) with RTPK and came up with the same results as John. I then processed all points with raw GNSS data in DPOS and the points 1204, 1205 and 1206 now match the RTK observations of 1224, 1226 and 1227.

 

[Alexey Razumovsky]

Last week we've uploaded RTPK v.4 on DPOS. What RTPK version was running on your TLS?

 

[John Thompson]

I don't know how to check RTPK version on the TLS.

 

[Michael Stazhkov]

I don't know how to check RTPK version on the TLS.

When you send the project to support it also gives the J-Field version and so RTPK version for us (you were using the Release version with RTPK v.3).
Alexey asked Matthew to be sure he is not using the PreRelease version.

 

[Michael Stazhkov]

Just in case, the RTPK version you can see on the bottom of the "RTPK Usage" screen. But the J-Field version is also enough.

 

[Michael Stazhkov]

RTPK v.3 had some issues that were fixed in RTPK v.4 (DPOS now is using the RTPK v.4). But your project helped Alexey find a problem with the new RTPK v.4 for some short files, which he is fixing now.

 

[APADDEN07]

Noticed a similar issue today. DPOS'd the job and noticed a +/- 10' discrepancy between RTK and PPK fixes. I took 3 shots here (9130.1 9130.2 9130.3) and all 3 iterations of the RTK agree w/in 0.1', but two of the PPK points have this big difference. I used "post-process selected point" after DPOS and the new RTPK coordinate matches the RTK... I was under the impression that PPK and RTPK coordinates should be "relatively" the same because they're being processed the same way...

If something has changed between RTPK and PPK it would be good to know, since we're usually counting on RTPK heavily to increase productivity in the field.

LS+ & T3 Base Running RTPK version1.75.1.91 J-Field 3.0.11.816

 

[Michael Stazhkov]

Noticed a similar issue today. DPOS'd the job and noticed a +/- 10' discrepancy between RTK and PPK fixes. I took 3 shots here (9130.1 9130.2 9130.3) and all 3 iterations of the RTK agree w/in 0.1', but two of the PPK points have this big difference. I used "post-process selected point" after DPOS and the new RTPK coordinate matches the RTK... I was under the impression that PPK and RTPK coordinates should be "relatively" the same because they're being processed the same way...

If something has changed between RTPK and PPK it would be good to know, since we're usually counting on RTPK heavily to increase productivity in the field.

View attachment 12147View attachment 12148View attachment 12149

LS+ & T3 Base Running RTPK version1.75.1.91 J-Field 3.0.11.816

The current release version of J-Field uses the previous version of the RTPK (v.3). DPOS service was recently updated with the new RTPK engine version (v.4).
We are now testing the J-Field version with the new RTPK v.4 and will release it ASAP.

 

[avoidthelloyd]

This is spooky. Following.

 

[Michael Stazhkov]

This is spooky. Following.

As I know some issue with the new version of the RTPK (v4) was found and it is already fixed in the testing version of J-Field. RTPK engine on the DPOS side also will be updated later.

 

[Michael Stazhkov]

Noticed a similar issue today. DPOS'd the job and noticed a +/- 10' discrepancy between RTK and PPK fixes. I took 3 shots here (9130.1 9130.2 9130.3) and all 3 iterations of the RTK agree w/in 0.1', but two of the PPK points have this big difference. I used "post-process selected point" after DPOS and the new RTPK coordinate matches the RTK... I was under the impression that PPK and RTPK coordinates should be "relatively" the same because they're being processed the same way...

If something has changed between RTPK and PPK it would be good to know, since we're usually counting on RTPK heavily to increase productivity in the field.

View attachment 12147View attachment 12148View attachment 12149

LS+ & T3 Base Running RTPK version1.75.1.91 J-Field 3.0.11.816

Could you send the project to support? We want to be sure that the latest RTPK will process your data correctly.

 

[avoidthelloyd]

As I know some issue with the new version of the RTPK (v4) was found and it is already fixed in the testing version of J-Field. RTPK engine on the DPOS side also will be updated later.

I know it will get resolved quickly. You folks are the top of the ladder and the feedback us users give (like this post) help keep things working like it should.

 

[APADDEN07]

Sure thing, project is UHW #2 sent from LS 00195 just uploaded to support.

 

[Wes Hand]

Sent project 1429 ROBINETTE to support.

Not sure if issue is resolve but this data is from Wednesday 11/10/21. I had RTPK fixes way off from RTK.

 

[Michael Stazhkov]

Sent project 1429 ROBINETTE to support.

Not sure if issue is resolve but this data is from Wednesday 11/10/21. I had RTPK fixes way off from RTK.

View attachment 12150View attachment 12151View attachment 12152

RTPK in the testing version of J-Field gives results close to the RTK solutions for all 3 points.