GPS is not healthy with Airsim

ArduCopter Copter Simulation
1

Hi everyone,

I’m trying to simulate ardupilot with airsim simulation. I’ve installed an ubuntu 18.04 in my machine and I’ve installed all the prerequisites by Tools/environment_install/install-prereqs-ubuntu.sh script. I downloaded the binary “Blocks” from airsim main page.

Everything works fine but when I send a command to takeoff (for example), the console shows the next message:

APM: PreArm: GPS is not healthy

what is my mistake here???

thank you all

2

Hello

Yes I confirm, I have this APM: PreArm: GPS is not healthy error as well.
I reverted to 4.2 and it works ok

@rajat2004 are you still active on the dev ?

3

I’ve had frequent GPS not healthy errors before, but they generally clear after a few seconds, just initializing I guess. Haven’t kept myself up to date with exactly what changed in between, maybe the GPS checks got a bit more tighter?
I’ll try out the latest AP master and test, will post if there are any updates. But might take some time, potentially next week.

@ppoirier Yeah, still active, but less frequent since semester is going on and too much of stuff to do, mostly responding on some issues or small bug-fixes, rebasing old PRs, and some review stuff.
One possibility could be that AirSim follows a simpler conversion from NED<->GPS, this issue has some info and links, might be causing the problem.

4

OK I got it , The SITL directory has changed and we need to take the parameter file directly from default :

cd ardupilot/ArduCopter
…/Tools/autotest/sim_vehicle.py -v ArduCopter --console --map --add-param-file=…/Tools/autotest/default_params/airsim-quadX.parm

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5

well… no there is something deeper into this issue
for the moment , revert back to Copter-4.0

Or DISABLE ARMING CHECK :slight_smile:

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7

hello，how to DISABLE ARMING CHECK? thanks

9

@haoepng set param ARMING_CHECK to 0

@ppoirier did you find out what the issue was here?

10

for beginners (and I am one) the exact line is:
param set ARMING_CHECK 0

PS: Only use this in simulation, there is a reason for ARMING not to work and it needs to be found before a flight.

11

I debugged the code around AP_GPS::is_healthy() in Copter4.4 SITL with AirSim and it turned out that the state[instance].lagged_sample_count started to rise above 5 so the delay_ok param caused the not healthy flag. The solution is to raise the expected_lag in AP_GPS_Backend::check_new_itow, which can be done by changing the default airsim param of GPS_DELAY_MS in airsim-quadX.parm from 20 to e.g. 200 (this is what I got as lag in my case). This could be indeed a permanent change in the repo’s param file not to cause further errors for everyone…

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