The parsed TilesetJson.
The vertical CRS WKID, or undefined when the tileset declares none. Feed the result to
datumFromVcsWkid (@bitruvius/maplibre) to auto-place a 3D-Tiles dataset by its true height.
3D Tiles itself defines no vertical-datum field: content is positioned into ECEF via
root.transform and heights are ellipsoidal by construction, so any orthometric-referenced
dataset conveys its datum out of band. Extensions are the spec's sanctioned mechanism for that,
and two publishers use it:
extensions.ESRI_crs.vcsWkid, a plain code. Preferred when present.extensions.SKYLINE_o3dml_Header, as compound WKT. original_wkt is the
dataset's own CRS; terrain_wkt describes the terrain it was draped on, so it is only a
fallback — seating against it would use a datum the geometry is not in.Reading both is conformant: SKYLINE_o3dml_Header appears in extensionsUsed, not
extensionsRequired, so a client may read or ignore it either way.
A tileset that declares nothing returns undefined, and that is deliberate rather than a gap to
paper over: the no-declaration population is not homogeneous. Google Photorealistic, Cesium OSM
Buildings and the ion photoreal meshes declare nothing yet carry ELLIPSOIDAL heights, while a
dataset like 3DBAG declares nothing and is already gravity-related (NAP). Any blanket default
would place one group correctly and the other wrongly, so the caller is told "no signal" and
decides.
Read a tileset's declared vertical CRS WKID.