Does anyone have idea how to make failsafe RTL when GPS fails? Here is some ideas:
If GPS fails ardupilot could calculate the distance and bearing to home using the init position fix and the last known position fix before the gps failure. Ardupilot could then take wind corrected magnetic heading towards home position fix and fly as long as the calculated distance would have been reached and then start orbiting with constant bank angle. Maybe with this method ardupilot could find its way close to the initial home position (Basic TIME/SPEED/DIRECTION based navigation).
Ardupilot could have some sort of radio signal direction finder which could be used to navigate towards transmitter signal (ADF/NDB-type navigation).
Ardupilot could navigate by using gsm cell based location information (DroneCell or equal could be used).
and....OPTION 4: Inertial navigation......
It sure would be nice to have a dead reckoning system in place. I can see a lot of drone thefts happening if all you have to do is flip on your cheap GPS jammer and follow the drone until it crash lands.
I think the most common situation is gps signal is lost for a short period of time. In those cases, loitering until gps-connection is re-established, and then continuing the mission would be the prefered solution. First after gps connection is not re-established after a given amount of time, I would want the mission to be aborted, and rtl to be initiated.
But, I do not have any idea of how the loss of gps sinal is actually handled in the programming of ardupilot, so also I hope someone with knowledge can enlighten us in this matter.
What happens when telemetry connection is lost?
Option 1 sounds like a very good option. However, I don't see the possibility of a long term GPS signal lost though. And the chance of GPS fail probably way lower than any other kind of failure from the numerous parts of the entire aircraft.
Concur with Veikko and Jake ... INS and/or dead reckoning would be great ... but in the absence of that, we need a GPS failsafe option (for the UAV we're designing) ... and I don't see anything in either the APM_Config.h file or the Arduplane.pde code for Arduplane 2.40 ... have seen in other threads and on other website forums that allegedly the APM 2.0 autopilot commands a loiter (to reacquire) GPS as a failesafe ... but I see no GPS safe ... what am I missing? ... we need it ... help!