proj6 and gdal3

[dbekaert]

@bbuzz31 @jlmaurer could we check how raider is impacted for this?
isce-framework/isce2#279 (comment)

[jlmaurer]

@dbekaert RAiDER definitely assumes GDAL3 at the moment and all the syntax assumes this.

[dbekaert]

@jlmaurer will add documentation before this can be clsoed

[jlmaurer]

Our current situation with PROJ, pyproj, and GDAL:

• Currently GDAL3 is required by the environment file. However, as best I can tell there is no GDAL3-specific code used in the repository. I believe we imposed GDAL3 for the purpose of being able to read and write HDF5/NETCDF files; however, we are not currently using GDAL to read or access those files in the code itself (not including dependencies)
• I checked the dependencies as well as possible. Rasterio requires GDAL 2.4 or later; geopandas requires Fiona (link to GDAL) and Pyproj but does not specify version dependency for GDAL, pyproj must be >=2.2.
• Pyproj may be a problem for some users down the line because the latest version requires Python>3.7 and PROJ 7. As long as users are using a conda environment there should be no issue, but other users may have problems.
• Our current pyproj requirement in the environment is 2.1.0, however this is not consistent with geopandas. We should require >=2.2 so we are consistent across the board and the "always_xy" argument should always get handled correctly.

[jlmaurer]

#319 addresses the pyproj dependency issue.

[jlmaurer]

This was actually addressed by #323