Mapping and GIS Solutions Community

We are trying to use Catalyst with the DA1 mounted to the roof of a car and are seeing a fairly regular accuracy reduction over time.  Startup is OK with the precision subscription (approx 3cm) but as we move the vehicle this degrades to 30cm after approx 10mins and down to 50cm after another 10mins, finishing at approx. 70cm after 30mins.  The vehicle is moving slowly (20-30mph) around areas with no tall buildings so signal loss was not really an issue.  Start and end point at the same position (it's a loop) and total distance approx 10km.  Has anyone tried the same sort of thing?  We wanted to try and understand why there is regular accuracy loss.

Hi Greg

The fact you are driving should not cause the accuracy to degrade unless the environment is causing an obstruction to the Catalyst antenna's view of the sky - In this case you could then have increased signal noise/ multipath/ poor geometry, all the usual GNSS limitations.

I'd say a more likely factor here is the correction source either falling back to something less accurate (in this case RTK to RTX) which can happen If your data connection drops for example or you run outside the VRS/NTRIP coverage area or  basic environmental factors, such as going through a tree lined street/ building shadow, increasing the noise and reducing the signal quality.

There are other factors we can examine, but to progress this and really give a good answer we would need the log files from Trimble Mobile Manager at the very least to take a look and see what happened.

I suggest you contact your Trimble Reseller and talk this through with their support team - please provide them the logs.

They should be able to help otherwise they can escalate it to Trimble directly

To close this one off...

After examining the log files - the device went 'offline' for an extended period during the session

With no data connection, the corrections from the VRSNow network stopped and the Trimble Correction hub reverted to SBAS.

This explains the changing accuracy from a 2cm RTK fix solution to a sub-metre differential solution.

As soon as the device was switched back online and had a data connection, the Trimble Correction hub re-established communications with the VRSNow network and Catalyst delivered a 2cm RTK fix solution again 

Hi,

Yes thanks for following up on this.  As there are several phones used with the system we simply did not realise that

the one in use had the SIM removed.  So we had a precision level accuracy at start as we were close to office WiFi

and then as we moved we did not have mobile data.  We tested again and all is fine on a different phone.

Much appreciated.

Best regards

Greg.

Greg Warren

Applications Engineer

t: + 44 (0)1949 831 814

e: greg.warren@geoslam.com | w: geoslam.com