I read the advice below for calculating geometric error. My tiles are pure terrain, I can easily find out total height from bounding box but biggest feature width is tricky/slow. Anybody has done that?
The geometric error can be computed however you like, but often a good estimate is finding
the diagonal of the largest building/feature in the tile.
In tileset.json a tile's geometric error will often equal the largest geometric error of its children.
https://github.com/CesiumGS/3d-tiles/issues/162