Make empty CRS possible

[evetion]

sdsl23

And set it to the engineering crs?

[visr]

What is the engineering CRS? Do you have a reference?

[evetion]

See https://github.com/geopandas/geopandas/issues/3019

[edzer]

What is the engineering CRS? Do you have a reference?

engineering CRS means it can be anything, but is metric (distances in Euclidian space, not angles). See e.g. Iliffe & Lott

[visr]

Thanks, that goes on my reading list.

[rafaqz]

So to calarify: we need no-arg constructors that insert the engineering crs for epsg/wkt/proj etc ?

[edzer]

So to clarify: we need no-arg constructors that insert the engineering crs for epsg/wkt/proj etc ?

The engineering CRS (wkt in geopandas issue) needs to be inserted when you write a GPKG using GDAL and you want to avoid that GDAL sets a long/lat, geodetic coordinates CRS to the GPKG, which it does by default.

Whether you want to use that WKT more general is up to you; R/sf uses an NA crs, but tries to convey to users that in such cases the coordinates are assumed to be projected and not geodetic. I think it is useful that that assumption is made clear.

[rafaqz]

Yeah sorry was unclear, that was more a technical question for @evetion about the issue as Im not sure what is actually actionable here.

Users/other packages like ArchGDAL/Rasters can already construct such a wkt to pass to gdal manually, the question is if the idea is to make that easy with no-arg constructors.

So e.g. WellKnownText() means the engineering crs.

[evetion]

Yeah, so either always use the eng.crs. when unknown, or use an NA one (unknown) and only set eng.crs when writing to file?

Relates to #30 as well (spherical/cartesian) as type parameter.