Arducopter 4.2.0 3D GPS Fix but unable to arm PreArm: GPS: waiting for home


I build a quad with Arducopter 4.2.0 and it says 3D GPS Fix but it’s unable to arm “PreArm: GPS: waiting for home” and it has 8 sats.

Why is it waiting for home when it has a 3D fix?

Hi @Ojwhaaa_Ojwhaaa,

Beyond just having a 3D fix, the EKF requires the GPS, accelerometers and compass values to be consistent. If you’re testing inside then it may be as simple as moving outside to resolve the problem. If this is a new autopilot then make sure you’ve calibrated the accelerometers.

Im setting up a Helicopter, at this stage I just need to fly in stab mode as the GPS has not arrive yet. Will I still be able to arm the copter if I update?

Hi @HeliRick,

Yes, the vehicle should be arm-able in Stabilize mode without a GPS. If the vehicle fails to arm it should print out a message with the reason why.

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I bought a new GPS, recalibrated everything again, it has 12 sats, but I cannot arm it in POS HOLD, it always says “PreArm: GPS: waiting for home” even when going outside.

EKF is all white and looks just fine, the only thing in red is the “pos_horiz_abs_Off”

What else can I do, what is the problem?

PosHold requires good positional accuracy. An HDOP of 1.2 is not good. Just because it says “3D Fix” in the HUD does not guarantee that. Wait until you see these messages:

Thanks for the help, I think I found the problem, it’s a new flight controller, and it constantly says “Bad baro health” in the log I think I have a monday morning version of the Matek F405-SE…

As far as the HDOP, for what I read is a HDOP below 5 acceptable, below 1 is perfect, so I really think the barometer is the culprit here

No way. Below 5? Below 1 is acceptable. The message in the HUD you posted is a positional/GPS problem it has nothing to do with the barometer.

The Wiki says " High GPS HDOP : the GPS’s HDOP value (a measure of the position accuracy) is above 2.0 and the vehicle is in a flight mode that requires GPS and/or the cylindrical fence is enabled"

So I guess everything below 2.0 isn’t High GPS HDOP and should not prevent a decent home location.

But the constant bad baro health message indicates a bad barometer…