We have been having issues this past month with maintaining an RTK Fix. Hardware involved is a Facet as the temporary base, Express as the rover both with LaRo Serial Kit 915mhz radios and using an android tablet running Lefebure NTRIP Client app. Base and rover are within 100 meters and line of sight of each other at all times. When connected the fix type will bounce between Fixed and Float every 3 to 15 seconds. Sometimes it will lock on and stay fixed at 14mm accuracy for several minutes or hours at a time. When I switch to running off the local NTRIP server (unplugging the radio from the Express and using Bluetooth RTCM delivery), either using single base line (less than 3 miles to the base) or network solution it still shows the same unstable behavior and will bounce between RTK and DGPS every 2-3 seconds with Float showing up occasionally. I have 4 identical setups having the same issues. What messages should I be monitoring or what settings should I look at changing?
Are your antennas in open sky position? Can you show us pictures of them?
Is the progress bar in Lefebure running smoothly?
When I switch to running off the local NTRIP server (unplugging the radio from the Express and using Bluetooth RTCM delivery), either using single base line (less than 3 miles to the base) or network solution it still shows the same unstable behavior and will bounce between RTK and DGPS every 2-3 seconds with Float showing up occasionally.
Ok, so it’s not the radios.
I have 4 identical setups having the same issues. What messages should I be monitoring or what settings should I look at changing?
Doesn’t sound like a single hardware failure.
When the Facet has enough RTCM to obtain RTK Fix, it can continue with RTK Fix for up to 30 seconds without RTCM before the ambiguities become so big, that it will slip back to RTK Float. This is not what you’re experiencing so I’m a bit confused. I want to blame Lefebure as it’s the only thing in the equation I’m not totally familiar with.
Looking at the Facet, do you see a solid double cross hair (indicates RTK Fix)? Or is it blinking (RTK Float)?
When in doubt, revert to a known good toolchain. I recommend switching to SWMaps just for testing. Connect to a local base station and push corrections over Bluetooth from within SWMaps. If you get a solid RTK Fix there, then I think we need to start looking at Lefebure and how it is detecting the RTK state the connected device is in.
In my experience these issues are cause by either (1) a spotty comm link between the base and rover and/or (2) poor sky visibility or multipath issues.
It sounds like you may have ruled out comm link issues, so how is the sky visibility? Are both your gps units seeing wide open sky? If you have to rove in the woods, is at least your base unit seeing wide open sky like Eric asked?
And is the display on the Facet showing the switching between fix and float like Sparky asked?