Need ability to convert 3D coordinates

[whitefractal]

Proj::convert assumes 2D coordinates, and passes z: 0.0 into proj_sys (which handles 3D just fine).

This is insufficient for conversions to/from (e.g.) ECEF coordinates, where the z coordinate is critical even for locations on the ground.

Then need to access the private c_proj makes it impossible to define a trait with a minimally-modified convert method which takes a 3D point, passes all three values in/out of proj_sys, and returns a 3D point.

Some provision for 3D coords within this crate would be extremely helpful please :-)

[lnicola]

Yeah, we should definitely support 3-4D transforms, it's just a question of API design.

[lnicola]

CC https://github.com/georust/proj/issues/121

[urschrei]

I agree but I don't have time, so (and I mean this in the most constructive way) if you want it, you'll almost certainly have to write it.

[balazsdukai]

I have a fork that I adapted for 3D coordinate conversion, specifically, because I needed to reproject to ECEF @whitefractal .

Here is the proj.rs fork. Here is an example how I use it.

In my adaptation, I did the minimum necessary for my use case. However, because the current Coord is 2D only, I'm not sure if adding additional members (eg z), would break anything downstream. What do you think @lnicola @urschrei ?

But if you don't see big hurdles in the API, I'll implement the 3D across proj and send a PR.