That's the next best step to take and try to answer.
We can begin where I think the heart of this issue begins.
Do we look straight ahead and see the horizon at eye level or are we actually looking slightly down at it?
--Dave
I've given you a way to determine that a while back, Dave.
Here it is, works best with a camera or some sort of lens system to look through.
Take a camera that can be mounted on some sort of pivot point, say, a tripod.
Ensure that the pivot point is completely level.
Look through the camera (or other device), and rotate it 360 degrees.
If the center of the camera is below the horizon, you're altitude is too low, move to a higher elevation; Or if part of the horizon is below, but the other part is above or if the distance from the center of the camera to the horizon is not equidistant, your pivot point is not level, and needs to be adjusted.
If the center of the camera is on the horizon, but not above, throughout the entire 360 degrees, then our eyes are looking out parallel to the ground at the horizon.
If the center of the camera is above the horizon all the way around the 360 degrees, then the horizon is dropping away the farther away it is, and when we look at the horizon, we are looking down at it.