I have an APM 2.6 flight controller and a 3DR GPS/Compass. I have a constant problem, not an isolated incident related to space weather. The HDOP drifts up and down between roughly 1.2 and 4. As a result, the GPS position drifts all over the place by 15-20 feet. There is no correlation to weather conditions, k-index, etc as this happens 100% of the time for over a year. It happened on my 3DR Y6 frame and now it's still happening on my modified FY680 frame. It happens even on the ground without the motors running. I can power up the APM on the ground and let it sit there for an hour logging it's location. Sitting there on the ground, not even trying to move, the GPS location moves all over the screen 15-20ft. The results in flight are as you'd probably expect. It moves around 15-20 ft in random directions chasing it's own location drift. I even bought a new GPS/Compass module hoping it would fix it. Nope, no change.
My first quad that I built using this hardware was rock solid. It never drifted so much as a foot. It suffered a violent death when a propeller failed at 150ft sending it crashing through the trees to the ground. The frame, battery, and plastic propellers were all destroyed in the crash. The APM, all electronic modules, motors, speed controllers, etc all survived seemingly unscathed. I've had all of it repurposed into a 3DR Y6 frame and my new FY680 modified Y6 frame. In both new builds since the crash, I've been experiencing this HDOP drift. Could something have been damaged in the APM hardware that could cause this HDOP drift? The GPS module is new, so it isn't that. But the APM itself is original.
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Not that anyone is paying attention to this. But the problem was apparently the beat up APM 2.6 I replaced it with a Pixhawk and now it is rock solid. Same GPS hardware and everything. Only changed the FC.
Do you have any transmitters on the plane?
For example:
RC Receiver with telemetry.
Telemetry Radio
FPV Video transmitter
If so, make sure their antennas are at least a few inches from your GPS antenna.
If it's not one of those, I'd suspect your GPS antenna (the ceramic bit) got damaged in the crash. You should probably try another GPS.
I've already replaced the GPS to rule it out with no change. I happens even with the camera and video transmitter powered down, ruling out those. I don't think I've every tried it with the telemetry and RC receiver powered down to rule out that interference. Those get power from the APM, and I've never bothered to disconnect them. I will try that to rule RFI from those out. Both of those were involved in the crash as well.
Anyone?