Mapping and GIS Solutions Community

Hi, When using the precision level subscription and Penmap on a Galaxy S2; if I get an interruption i.e. tree cover and it causes loss of gps signal (not loss of internet), the system drops the correction down to the sub meter accuracy i.e. RTX correction. When moving back into the open it does not return to the VRS Now correction. If I shut the system down and restart it (log out of pen map and disconnect the DA1 from both the battery and the device) it still won't resume the VRS Now correction level i.e. in Penmap it reports differential rather than fixed position, and we are at sub meter accuracy.

The only solution to the issue seems to be to completely shut down the device, log out of everything, and disconnect power form the DA1, wait for a long time, then restart, and log back in, and try again. It may then work or may not.

This is a frustrating issue. While its good that the correction service identifies the interruption to the GPS signal and makes a fix to keep the system working, its no good to then spend 1/2 hour + trying to get back to the precision level of accuracy.

Any help or suggestions would be appreciated.

James.

Hi James,

the step down from VRSNow to RTX is the default behavior of the Trimble Correction Hub system - so this is 'as designed'. Typically this happens if you get out of the VRSNow coverage zone - in your case it sounds like the amount of SVs seen by both base (VRSNow station) and rover is below a certain threshold. 

The way up - from RTX to VRSNow is not done automatically. This is because RTX might be good enough for you current task - and its critical to 'kill' a RTX initialization to realize that VRSNow link is shaky. Therefore this is business logic within each application.

The way up is typically achieved via restarting the survey - so simply disconnecting in any software and then perform a reconnect (software reconnect, no need to pull the cable). 

This should get you back to VRSNow - and doesn't take longer then a couple of seconds (at least the disconnect - connect). 

I'll also inform the Penmap team so we don't have something else mixing in here. 

Regards

Nico

Hi Nic,

Thanks for the reply. I understand what you are saying and it makes sense re the step down behaviour. I’ve tried the simple disconnect and re-connect and it doesn’t go back to the VRSNow, despite being in a good coverage zone etc. I’ll try and keep some records of sat numbers etc. the next time it happens and see if we can find a correlation of some sort.

Thanks,

James.

Hi James,

Samsung Galaxy S2 is well below the minimum device recommended for Catalyst to properly function. The sort of behaviour you are seeing is a typical case of a phone struggling to keep up with the required processing load of Catalyst. When the phone struggles to run Catalyst, you will experience poor or loss of initialization, drops of satellites and degradation in precision.

[Advanced tip] If you look at the diagnostics.log under \sdcard\Catalyst\ directory you will likely see lots of lines containing the text 'CPU-Load'. These are one indication of the phone struggling with Catalyst. Note - it can be normal to see some of those messages in the log for a given Catalyst session particularly when doing CPU-intensive tasks while running Catalyst in the background

For Samsung Galaxy family, I would recommend a Samsung S6 or better.

Please refer to the Compatible Devices page for Catalyst for more information.

Regards

Joshua

Hi Joshua,

The device I’m using is the current / latest model Galaxy Tab S2 8 inch tablet, not the s2 phone. Its listed as a suitable device in your device compatibility requirements doco as attached and also in your quick start guide, both documents were provided to us when considering this system. Can you please confirm if it’s suitable or not.

Thanks,

James.

Thanks James. We have tested Samsung Galaxy Tab S2 8.0 and found it to perform more reliably with Catalyst when the DA1 is the host instead (powered by battery prior to connecting the antenna to the device). 

If you were actually referring to (Samsung) Galaxy Tab S2. Please dismiss my previous comment.

Depending on the Galaxy Tab S2 model, it does have some known performance issues when the device acts as the host for the DA1 antenna (where the phone mainly supplies power to the DA1).

While operating the device as the host, depending on device used and the operating system installed, it can sometimes toggle back its CPU to save battery and can sometimes result in Catalyst under-performing.

This can sometimes be prevented by having DA1 as the host instead. To do this, connect an external battery to the antenna first before connecting your device to the antenna. If done successfully, the battery icon on your device will typically show a 'charging' icon.

Hi Joshua,

Yes it is the Tab S2 and I have been connecting the battery to the DA1 first and ensuring the charging icon is showing on the tablet.

Thanks again.

James.

Thanks James, that narrow things down.

Providing that there is no internet outage as you suggested, poor (re-)initialization performance can depend on a few common factors:

• Heavy load or CPU toggling or incompatible phone (now likely to be ruled out)
• Satellite availability at rover which can vary depending on time of day. i.e. you may find favorable initialization performance in the morning but not in the afternoon, or the other way around. It may help to check how many satellites are being tracked and used in the RTK solution at a given time. 
• Poor satellite geometry depending on user's surroundings and time of day.
• Distance to nearest physical base station

One may typically find that Catalyst will initialize okay in a reasonably open sky environment, and after walking into or near trees (obstructions to the sky) the performance degrades.