I’m using an RTK Express with internet access. I’ve done it both with a cell phone running SW Maps and using the NTRIP client and the internal wifi connection and NTRIP client.
On a government data source located about 36 miles away (closest they had), I was never able to get beyond RTK Float (eg, never hit RTK Fix). It was outside in a clear field on a clear day with 31 sats being tracked and was downloading a bit of data every second or so from the internet. SW Maps showed it was doing the transfer.
I switched to rtk2go which had a data source about the same distance away, and it did hit rtk fix pretty promptly…So I’m curios about that.
Then later, I had the RTK Express connected via wifi to my phone and internally specified the RTK2go connection and same mount point, when actually trying to do some measurements. It was on rtk fix for a while, then in areas, it went to rtk float for a while, then switched back and forth a bit. I was working around some 1-3 story buildings, so there’s the possibility of shadowing some satellites, but I still usually had about 20 sats being reported on the RTK Express’ s screen.
So, what are the things that can cause a switch to RTK float?
We generally recommend a base station within 10km (6 miles) for the best accuracy but 20km, even 50km has been shown to achieve RTK fix but it’s rare. I am not surprised that you where in RTK Float with a station 36 miles away.
Similarly, with lowered reception (sky occlusion due to buildings), the receiver will do its best, but will drop to RTK float if it can’t resolve all the unknowns.
Sparky’s answer is spot on. The buildings may have also caused multipath, where the receiver is receiving signals reflected off the buildings. Multipath can be much more problematic than occlusion (shadowing) as the receiver is getting time-delayed signals which can cause problems with the calculations. You might try increasing the elevation mask (to 15 or 20 degrees) and see if that helps; sometimes it does, sometimes it doesn’t. You could also try going back a few hours later when the satellites have moved around a bit.
toeknee probably knows more, but I usually a hodge podge. The older stations relied heavily on GPS and GLONASS. Lately, I’ve seen a shift away from GLONASS towards Galileo. But I believe most modern stations report everything possible - GPS, GLO, BDS, GAL, QZSS, NAVIC, the list goes on.
