May P3D sometimes take more than 8 seconds to load scenery and the associated local elevation?
Easily. There is something in our favor though:
P3D tends to load scenery in a progressive way - it'll load a very rough terrain model (so the ground elevation will be near, but not at, it's true value), then slowly load more detailed terrain. As long as I can send repeat Qi198 updates during the 1-8 second period then that's ok.
(Reason: the ground elevation I send will probably change over this 1-8 second period as P3D loads progressively more detailed terrain models. There is value in using the initial rough terrain model ground elevation - it presents a good starting point for PSX to begin slewing towards)
The initial ground elevation value should arrive at PSX within 8 seconds (though this will vary depending on the user's PC capability. If you're implementing another variable, then being able to go higher than 8 seconds may have value as a user-settable option in my software).
From the perspective of PSX.NET P3D ExternalSim, I will probably be looking to send the 'special' command at these points (this is a rough guess, please make any suggestions):
- When it first loads and receives the first ground elevation value from P3D
- When lat/lon changes massively in a short time frame
- When I receive 'load3' from PSX