I'm really hoping that someone in the community can help a fellow drone hobbyist figure out this GPS mystery.
I have an Ardupilot Mega 2.0 (Ardupilot 2.50) with an external MediaTek MT3329 GPS (3DRobotics) to this point seemed to be working very well together. Yesterday I nearly avoided a crash when midway in a mission I started loosing my GPS lock and the plane really lost it's mind. Only by grabbing manual control (timestamp 3:49) was I able to regain some altitude and let it get it's GPS lock again. There was enough of a lock to resume the mission, but this loss of GPS really makes me worried about attempting some of the more aggressive projects I have planned. Normally I have a GPS lock of 9-10 satellites, and I'm not used to loosing GPS in the middle of a flight.
I made a video of the event and combined the Mission Planner, Telemetry, and Live View.
YT 01:59 - Cam 17:38:00 - MP 17:29:03 - Loss of GPS to 6 Sat
YT 02:49 - Cam 17:38:50 - MP 17:29:53 - Loss of GPS to 6 Sat
YT 03:14 - Cam 17:39:15 - MP 17:30:18 *** - Loss of GPS to 4 Sat
YT 03:49 - Cam 17:39:49 - MP 17:30:53 *** - Emergency Regain of Control
YT 03:50 - Cam 17:39:51 - MP 17:30:55 *** - Loss of GPS to 4 Sat
YT 04:13 - Cam 17:40:13 - MP 17:31:17 - Resume way-point mission
YT 09:17 - Cam 17:45:18 - MP 17:36:22 *** - Loss of GPS to 7 Sat
YT 09:40 - Cam 17:45:41 - MP 17:36:45 *** - Loss of GPS to 4 Sat
YT 10:36 - Cam 17:46:16 - MP 17:37:40 *** - Loss of GPS to 6 Sat
YT - YouTube / Cam - Camera Timestamp / MP - Mission Planner
Here is an image of my electronics pod:
After this near-incident I have a few questions:
- Is this a potential GPS multipath problem since I way flying over a parking lot and a flat building?
- Does Geo-fencing operate when I am in a auto (mission) mode?
- Does Geo-fencing operate if I suddenly am outside the fence without the APM "seeing" the fence breach?
- Will the new firmware 2.60 with dead-reckoning help prevent these sort of issues?
- At what point with dead-reckoning be preferred of a weak or lost GPS signal?
- Is my telemetry or radio receiver placement a problem to the operation of the GPS unit?
Here is my telemetry log where the plane appeared to be flying "backwards" on the telemetry screen where I started loosing my satellites:
Any help would be GREATLY appreciated!