[PROJ] "Local" projection method?

[Kristian Evers]

Nyall,

> 
> Based on this, would it be appropriate to directly map this projection
> method across to the "Orthographic" method? Or am I missing something
> important?…

Yes, it would seem so. Be aware though, the current Orthographic projection
implementation in PROJ is only valid in the spherical case. You would have to
extend that to the ellipsoidal case for the mapping described by Esri.

We’ve got an old issue [0] which contains some hints on how to go about that.

/Kristian

[0] https://github.com/OSGeo/PROJ/issues/397