[PROJ] How to use PROJ for vectors and rotations?

[Greg Troxel]

Nigel Stewart via PROJ <proj at lists.osgeo.org> writes:

> There is another aspect of PROJ and reprojection that we're looking at.
> PROJ is formulated in terms of points and our LiDAR offerings are very much
> concerned with gathering large quantities of those.
> Sometimes these points have an associated surface normal attribute, a unit
> vector.
> And sometimes we have points with an associated quaternion rotation: (or
> yaw, pitch, roll)
>
> Is there known math and/or code for applying PROJ to these domains as well?
> For Helmert transformation it seems reasonable to use the rotation matrix
> directly.
> (Ignoring translation and scale)  But more generally?

Have you looked at the actual rotations that occur in transforms you
want to use, and compared them to the error estimates of your surface
normal/rotations?