A GPS predictor site won't kelp much as it would only show how many sats are visible with an unobstructed horizon and what you are planning would in effect block the view of half of the sky.
But it's a simple matter to watch the sat numbers on your app as you descend and if you lose enough to be close to dropping out of P-GPS mode, it would be a simple matter to climb higher if you wanted to maintain GPS.
There is no default option for loss of GPS because there's not much you can do about it.
You lose GPS and your Phantom is now in atti mode. That's about all there is to it.
In post #11 you talk like you anticipate losing control signal and GPS together but that is unlikely.
They are two different systems and not related.
It's good that RTH is simple because too many options would just confuse matters
I agree the GPS animation will probably not be of much help when descending close to the cliff face.
When you say "you talk like you anticipate losing control signal and GPS together", you are misinterpreting my expectations during my flight. Being a very conservative pilot, I am simply trying to anticipate the possible problems I might run into and what I will do in those situations. I absolutely do plan on watching the sats and RC connections, and aborting if I see a problem arise with either. However, flying down a sheer cliff I may go from full connectivity to none in a few seconds.
Now when you say... "There is
no default option for loss of GPS because there's not much you can do about it. You lose GPS and your Phantom is now in atti mode. That's about all there is to it."
That is where my suggested changes would IMHO be very helpful. You could indeed do a great deal about it if my suggestions were implemented. You would go from "there's not much you can do about it." to having a world of options.
I think we would agree that most fly aways and crashes can be traced to pilot error, so if we proceed with this discussion assuming that there is nothing wrong with the P4 itself then as I stated earlier increasing altitude would most likely regain sat connectivity and initiate a safe RTH. No lost drone and a happy ending!
If flying over water on a small lake surrounded by trees that caused the loss of sat connections for example, I can see no argument where autolanding is a better option then increasing altitude to regain sat connection. Just because you are higher does not increase your chances of hitting something before regaining control any more than drifting as the bird auto lands whow knows where would. I would posit that increasing altitude would be safer since in all but the very extreme circumstances the increased altitude would clear the obstructed view of the sats and RTH. The autolanding with uncontrolled drift would be more of a roll of the dice. As for the increased complexity of the additional options, I believe most people would never touch them, but for those more capable pilots it would be a lifesaver. I don't believe in dumbing down the bird for those who are not competent to use these advanced features.