I fly a P4P in West Virginia. It is a mountainous region where if i fly just 100 yards from my home the elevation could drop as much as 1000 feet to the river. How do i safely fly in such a situation and what do my max altitude settings need to be
http://stevemyleswv@gmail.com

Generally speaking you should stay below the 400’ elevation.

But if you are flying below your take off position, I suppose that your flights can be at varying heights above or below your actual home position, of ground.


RedHotPoker

An interesting question. Not sure in your area, but recreational drone users in Australia are allowed up to 120 meters.

I asked one of the rangers at Mount Kaputar National Park the same question in regards to operating within guidelines in the park on Friday given that I would be flying over valleys.

His response was that the altitude height restriction as far as he was concerned was based on where you took off from. So if the lookout was at 1300 meters, you could fly up to 1420 meters. He did emphasis that this was his decision and that it may not apply to other national parks.

Looking at CASA's Flying drones or model aircraft recreationally, the regulations state You must not fly your drone higher than 120 metres (400 ft) above the ground.


So not very clear at all.

The P4P's altimeter is based on barometric pressure.  Setting the max altitude to 400 feet means don't fly higher than 400 above the level of the takeoff point. If you maintain 10 AGL (as displayed on the DJI Go app) as you head toward the river, the drone will stay at the same MSL altitude, however its AGL altitude will increase as the ground "falls away". If the river is 1,000 feet lower than the takeoff point, then when the dji app says 10 feet, the drone will be in fact flying 990 feet above the river.

There's no setting that will keep you safe or within the 400 AGL rule when you're flying from higher to lower elevation in such topography. However, if you start your flight at the river, and you plan to fly to your house, you must set the max altitude high enough (e.g., 1010 feet in this example), to enable the drone to continue to fly above the ground.

We don't have much info to go by.

You have to understand what AGL is, and you'd have to have an idea how low manned aircraft might fly in that valley.  It seems there is a good chance that it's possible for a manned aircraft to fly as little as 500 feet above that river, so you'd want to be sure to fly below that height.  FAA would like you to fly no more than 400 feet above the river at the maximum.  The spot you launched from has nothing to do with any of this.  

There might be other complications such as nearby airports, but we'd need to know your location.

Good luck

great one