Silly Question MSL vs AGL

[AgricultureAerial]

This may seem like a dumb question, but what is the formula for converting MSL to AGL? I appreciate all the help.

 

[PortCanaveralFlorida]

The MSL calculation is derived from observations of tides and seasonal variations over a 19 year period to arrive at the average MSL. A UAV that flies at 500 feet MSL and stays level will register as flying at 500 feet MSL -- no matter the terrain changes below the pilot.

could be wrong

 

[AgricultureAerial]

The MSL calculation is derived from observations of tides and seasonal variations over a 19 year period to arrive at the average MSL. A UAV that flies at 500 feet MSL and stays level will register as flying at 500 feet MSL -- no matter the terrain changes below the pilot.

could be to be wrong

Thanks for the reply. I understand what MSL actually is, but I guess my question is, how do i know what 4500 MSL is on a sectional chart? If our flight is regulated to 400 ft agl, and the class C airspace starts at 4500 ft msl, how would i know what 4500 ft msl is in actual AGL feet? Thanks again.

 

[droneseyeview]

Thanks for the reply. I understand what MSL actually is, but I guess my question is, how do i know what 4500 MSL is on a sectional chart? If our flight is regulated to 400 ft agl, and the class C airspace starts at 4500 ft msl, how would i know what 4500 ft msl is in actual AGL feet? Thanks again.

You have to know what your elevation is where you launch

 

[Dr. Ifly Drones]

Thanks for the reply. I understand what MSL actually is, but I guess my question is, how do i know what 4500 MSL is on a sectional chart? If our flight is regulated to 400 ft agl, and the class C airspace starts at 4500 ft msl, how would i know what 4500 ft msl is in actual AGL feet? Thanks again.

Airspace (4500' MSL) - Local elevation (variety of sources) = Your answer. So, if local elevation is +500' by map above MSL and class C is 4500; 4500-500=4000.