Dev. Idea - Improvement for arducopter and plane - GPS & Rally Points

I like the added safety those rally points provide during missions.
However, my understanding is it all relies on good GPS data. What happens if that is exactly the cause of the failure? …i.E. a GPS glitch or full GPS failure mid flight ?

  • In commercial aircraft the internal sensors (gyros) and navigation computer keeps track of all aircraft movements, speed and direction in order to calculate current position.
    Whilst this may not be practical in a drone due to often fast and sharp movements during some flights which may cause issues in regards to reliable position calculation, there might be away around this:
    –> Why couldn’t the latest reliable GPS data being saved every few seconds? Then, if there is a GPS related issue that data could be used to calculate the required direction and distance to the nearest rally point for safe landing.
    I do understand that the speed values are also missing once a GPS failure occurs, but using the last known speed and motor control settings would still allow for a reasonable accurate position calculation.
    Also in arduplane often an airspeed sensor is used anyway for independent air-speed readings.

FYI dead reckoning on gps loss has been available in Plane for a long time.

Thanks,
I’ve tried to get more detailed information on that but couldn’t find it.
Does it actually then calculate position and required changes to flight direction ?
…Or simply just recognise there is a GPS related problem but not able to fly to nearest rally point?
I know in Arducopter in Auto mode it will perform certain calculation in regards to next waypoint if GPS drops out, But I’m not aware it being able to completely re-direct drone to home or nearest rally point.