posted
There have been reports from Trimble RTK users on horizontal positions relative to CRTN Topcon receiver base stations being as much as 0.5' off in the east component. This was verified by myself by side by side comparisions using a Leica SR530 and Trimble R8. We believe it has nothing to do with the Topcon antenna models used in the Trimble software. The receivers having this problem have recently been upgraded with the latest firmware and software. Older versions have not been tested as to whether they are having the same issue. This message is a "heads up" to Trimble users and if you are seeing any problems like this, please let us know. We will do everything when can to help the Trimble users resolve this problem.
Posts: 28 | Registered: May 2006
| IP: Logged
posted
I have tested and verified this issue with respect to the data streams of the OCRTN only (I an unable to currently test this with the CRTN broadcast of the same stations). The easting value of a point, when calculated from one of the stations with a Topcon receiver by a Trimble R8 moves in an easterly direction about 0.01' every 10 seconds for about 21 minutes suddenly snapping back to the most westerly extent about 1.25'. This range appears to be centered on the "true" value. Northing and elevation do not appear out of tolerance.
I tested positions with 1 minute RTK observations using an old 5700 and saw errors in the similar range. I do not think it is limited to the latest receivers only.
posted
This is most likely a timing issue related to clock steering. Either the transmitted time tags are inconsistent with the phase and pseudorange data (unlikely since other receivers are okay with the Topcon data), or they are wrongly interpreted or dealt with by the Trimble receivers. More later. --Yehuda
Posts: 215 | Registered: Feb 2005
| IP: Logged
posted
Update: I was able to connect to the 3.0 and 2.3 RTCM streams of one of the OCRTN stations through the CRTN IP/Ports. The result was identical to the graph I posted above (west to east tracking position with jumps back 1.25). Additionally, I stopped the survey to switch from 3.0 to 2.3 and I noticed the gap was appropriate to the time it took me to switch over; essentially the position I was calculating was directly based on what time I was collecting.
To ensure the issue is not isolated to Topcon stations in the ORCTN, I'll have to travel to be in a good position to test an outside station.
-------------------- Rich Maher, PLS KDM Meridian Posts: 42 | From: OC, CA | Registered: Apr 2005
| IP: Logged
posted
After many field RTK tests with Leica, Sokkia, and Trimble receivers, the problem seems to be a "receiver clock bias" problem from the CRTN server software. I still don't see the problem with the Leica RTK receivers.
Posts: 28 | Registered: May 2006
| IP: Logged
UBBFriend: Email this page to someone!
Printer-friendly view of this topic
