^ ThisIt matters because the front sensors are not able to see all obstacles (e.g. power lines).
IMHO, you should always set your RTH altitude at least 50 feet higher than the tallest known obstacle since the altitude is only an estimate based off of data retrieved from the barometer.
Yes, since a rarely have RTH enabled, I leave mine at 120M (400') since it's practically impossible to estimate how high anything is when looking at it from a half mile away. I rarely go behind anything anyway, since that's a recipe for auto RTH. On a long distance flight I will sometimes turn the craft to look at my launch site to make sure I'm still LOS, when I'm not sure.I just always set mine to 150m. Better safe than sorry.
What the other responders have not taken into account is the fact that the RTH height is based on your take off point. This is very important. While as Msinger says, you should set your height above tallest object, if that object is sitting on a hill that is 51 feet above take off point, you have lost your bird. Take the highest object + the height (that object is) above take off point + 20% for safety = RTHWith the P4 having the front vision sensors and able to use those during RTH, why does it matter what the height setting is for RTH, since it will be able to avoid obstacles regardless?
And don't forget that you can adjust the height mid flight if you see a new obstacle
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