I had an idea for a breadcrumb based RTH system which would allow for return to home based on waypoints that have already been flown successfully. The basic idea would be to allow the pilot to flip a switch on his transmitter at several points during flight, and if RTH is enable the plane would return to home along a known good path. Is this possible?
+1 on that one !! :-)
Based on a previous commercial system I worked on, a few additional suggestions: 1) capability to enter onto the inbound plan at the nearest waypoint, rather than a fixed "entry point"; and, 2) the ability to define a spatial volume within which any RTL behaviour is acceptable.
The first means that your vehicle won't do unreasonable things such as head further outbound to start RTL. The second is more involved but can be achieved using a variety of techniques, such as a volumetric nav mesh and online planning.