Hi,

no he internal coordinate system is not the LSE CS. For a given point O, the LSE CS is tangent to the ellipsoid at position O with Xlse pointing east, Ylse point north and Zlse up. However it is is tangent at ellipsoid with h or Z 0..

In example the blue axes are the LSE CS for point region center but at 0 height while project is at h 268...the red axes are the internal coordinate system.

So if you have:

T = chunk.transform.matrix

L = crs.localframe(Ogeoc) where Ogeoc are the geocentric coordinates foe a given point O

then T goes from Internal CS to Geocentric CS and L goes from Geocentric CS to LSE CS for given point O.

As for geocentric CS it is a cartesian orthogonal centered at earth center and values in meters with Xgeoc pointing to Greenwich meridian and Zgeoc to North Pole... That is why values are in the millions as on earth surface we are sone 6 million meters from center see 2nd attachment...

So if you transform geographic coordinates (long 0, lat 0, h 0 )) to geocentric you will get radius of elipsoid at equator for Xgeoc. And from lng 0, lat 90 and h 0 you will get radius at North pole (semi minor radius) for Zgeoc.

`In [10]: crs.transform(ps.Vector((0,90,0)),wgs84,wgs84.geoccs)`

Out[10]: 2023-12-09 17:06:13 Vector([9.52360149646502e-09, 0.0, 6356752.314245179])

In [11]: crs.transform(ps.Vector((0,0,0)),wgs84,wgs84.geoccs)

Out[11]: 2023-12-09 17:06:44 Vector([6378137.0, 0.0, 0.0])

Hope this helps...