By the way, there might be a way to determine the actual terrain height in MSFS with the existing SimConnect API already. I haven’t tried it out myself so far, but I have been told that this a “long proven design pattern” (since the beginnings of SimConnect in FS X ;)).
In essence:
- You place a “probe” - an AI aircraft or the user aircraft itself - at the desired location (latitude, longitude)
- You get the “ground altitude” value at this location (with SimConnect_RequestDataOnSimObject), simulation variable: GROUND ALTITUDE (presumably - and pay attention to the units: most altitude data is in feet, but according to the description this one is in meters)
I am just not sure how the value depends on the scenery / mesh data, specifically whether you need to “wait” at the desired location until the mesh data is sufficiently refined (by being downloaded from the mesh servers) - or whether that altitude data is available immediately (from elsewhere - regardless of the download status of the terrain mesh).
For details we can discuss this further in the SimConnect forum, specifically check this thread here 