Am I correct in the assumption that as a tile sub-divides the vertices of the parent tiles don’t change height, only that the middle of the parent tile becomes more and more defined? So the 4 vertices of the parent tile remain fixed and dividing into 4 children simply adds 5 vertices (each child shares one verticie with it’s parent.) As opposed to vertices being approximate averages at low detail levels and potentially bouncing around at each detail level. It would be nice to save locally a certain amount of geometric detail of a specific region, then only load sub-divisions as the camera either gets close to or FOV-zooms closer, and the fixed system would work very well with this scheme.

I also assume that flat-lands have less tile sub-division levels than do hilly regions, while places with steep grades have the highest number of sub-division levels.

It would be a nice option to see shaded tiles, possibly in a checkerboard fashion. No textures, rather colored polygons to easily see exactly what is occurring geometrically. This would be better than a wire-frame.

I assume geometry tile servers use geodetic lines of latitude and heights are relative to a reference ellipsoid like WGS84 in the direction of the surface normal. Perhaps some tile servers give the option for geocentric latitude and heights relative to a reference sphere? It’s around a 20000 meter ellipsoid height difference from Challenger Deep (-11000) to Everest’s summit (+9000) There’s also only a 0.03364% difference between the polar radius and equatorial radius (~21000 meters.) So using a spherical reference model seems reasonable, at least as an option.