How to convert projection

[musicformellons]

As I do encounter mentions of SRID in the issues and docs I am a bit puzzled if this library can also convert from one projection to another? Or would I need to use it in combination with https://github.com/georust/proj and if so, is there an example maybe how to do that?

[michaelkirk]

geozero is principally concerned with reading and writing different formats of geospatial data, but it doesn't really have any facilities for transforming the data.

Or would I need to use it in combination with https://github.com/georust/proj

That should work! The specifics will depend on what your input and output are exactly.

proj crate knows how to work with geo-types geometries, so my approach would probably be something like:

1. use geozero's geo-types reader, depending on your particular format (see the proj README for examples)
2. use the to_geo method to get geo-types geometries
3. use the proj crate to project the geo-types geometries to whatever SRS you want
4. use geozero to write back to whatever supported format you'd like

[frewsxcv]

There's now a Transform trait in the proj crate (and also reexported in the geo crate) that you can use that will make this a little simpler https://docs.rs/proj/latest/proj/trait.Transform.html

[michaelkirk]

I don't think there's anything left to do here, so closing.

[michaelkirk]

@musicformellons - I actually ended up trying to do something like what you mentioned and had a hard time. 😅

I was able to go from geojson -> geo_types -> proj -> geojson easy enough.

But the complication I encountered was that I didn't see a non-terrible way to maintain the geojson's properties (since they are lost at the "-> geo_types" step.

Did you end up getting something like this to work?

[musicformellons]

@michaelkirk I think in the end I might not needed it. I see only 'proj' and 'geo-types' in my cargo.toml. I was working with shapefiles. So can't help I'm afraid.