Allow tileset transform to scale geometric error

[lilleyse]

The tileset transform should be able to scale geometric error. The two areas in the spec that need to be revised are:

In specification/README.md

The transform property does not apply to geometricError—i.e., the scale defined by transform does not scale the geometric error—the geometric error is always defined in meters.

In tile.schema.json:

transform does not apply to geometricError

In CesiumJS, see CesiumGS/cesium#5330 and CesiumGS/cesium#7411

[pjcozzi]

This is a spec bug fix, please coordinate with @ggetz to see if it can go into the OGC Community Standard; otherwise, this needs to be versioned draft 1.0.1.

[ggetz]

This would need to go in v1.0.1

[javagl]

^{I think it was said to become an own issue, but it may make (more?) sense to just mention this here)}

When the tileset scaling is supposed to affect the geometricError, then it has to be clarified which scaling factor should be used in the case of non-uniform scalings (even though non-uniform scalings are probably rare in practice). Saying that the maximum of the three scaling factors should be used may be a sensible, conservative solution here.

[ptrgags]

@javagl good point about the non-uniform scaling, though if the matrix has both rotation and scaling, you really need to do a principal component analysis or Singular value decomposition to align the scaling factors with the axes.

I'm working on a PR for this, albeit finding the right way to describe this might get tricky