According to various forum posts, X-Plane uses geodetic latitude for reference points, but also assumes a “round” earth. This is a little confusing to me — Does it mean that given a reference lat/lon for a scenery map, the map is round (spherical) at its base, though the reference point itself is tied to an elliptical Earth model?

According to the tech notes…

“A few pitfalls of this coordinate system: the Y axis is not synonymous with up; this divergence increases as you go away from the reference point. Most parts of x-plane compensate for this, but there are still some shortcuts, typically for performance reasons.”

Does this mean that I can expect to observe unrealistic jumps in simulation time and/or Lat, Lon, Alt position data when crossing scenery borders — or in general when X-Plane detects a coordinate system shift? If so, would this be a CPU/GPU issue (which can be remedied, e.g. with a quad-core CPU) — or a physical modeling issue, or both?

This is important to me because I count on realistic progression of the aircraft dynamic state, and must bypass X-Plane’s autopilot in favor of externally computed steering commands.

Thanks
Bob