We are trying to use Reach in UAV for precision landing and loiter. Our setup:
- Navio2 with 4g modem.
- Reach RTK module connected to Navio USB port. We configure Reach-to-Navio USB internet bridge, so Reach has access to 4g internet.
- Tallysman TW4721 antenna on UAV (shielded with foil plate).
- Base station is the one provided by rtknet.ru service (NTRIP caster). The distance to the station is 7 km, sometimes we use another station which is 18 km far (unfortunately the first station can be off from time to time), the result is pretty much the same.
- ReachView and firmware are the last versions available.
- Selected GNSS systems are: GPS, GALILEO, GLONASS, SBAS. Glonass AR mode is off. GPS AR mode is Fix-and-hold.
Now to the problems.
- The best we could do to this point - fix with 999 AR ratio when UAV is on the ground (not armed) for several minutes. Fix holds pretty well, but if we reboot UAV or do some manipulations to cause a short interference, fix changes to float and stays there for a long time. The environment stays the same. Sometimes we just can’t get fix at all. SNR levels are stable with green bars from five to zero (usually 1-2 green sats).
- No fix after takeoff. Reach starts to jump between float and single, sometimes it leads to crazy UAV jumps.
Here are some screenshots of SNR chart and solution map (disarmed UAV):
The goal we’re trying to reach is reproducible, stable and pretty quick fix after UAV is powered. After that flying mission with precise landing will be initiated.
I understand that if we could not get stable RTK (even float) in the air we probably did something wrong. And can we rely on RTK for precision landing with up to 20 cm accuracy at all?