Net2Cog should not default to Web Mercator projection if CRS is not explicitly set.

[autydp]

I recommend removing the code that sets CRS to Web Mercator in the absence of any CRS in the source data.

• HyBIG will reproject if necessary.
• Most often, the absence of an explicit CRS implies Geographic (LatLon) projection, not Web-Mercator.
• RioXarray (CoGeo? - Cloud Optimized GeoTIFF package) interprets correctly (as Geographic) without CRS.

[autydp]

Note - if the original intention was for PO.DAAC's browse-image generation to always produce Web-Mercator images, I might suggest this be moved to the chaining implementation that calls HyBIG, or even the external invocation of that chain - where the CRS can be asserted in the request - rather than being burned into the Net2Cog implementation.

[frankinspace]

I agree, we can remove the code that sets CRS to Web Mercator in the absence of any CRS in the source data.

I think that made it in originally as I was messing with settings to try to get the image to display correctly (by 'correctly' I mean not-inverted #7. But I'm coming to understand that is not actually a problem).

[frankinspace]

• Related to above - CRS & Dimensions should be handled on a per-variable case, per-variable references.
  • e.g., SMAP L3 has xdim and ydim dimension variable names
  • Upgraded xarray and rioxarray/rasterio appear to handle CF conventions well - including SMAP
    • No need to implement add_crs after to_raster in all cases
    • Code currently assumes geographic grid and adds EPSG:4326 CRS
      • this should be special case - only if nc_xarray[var].rio.crs is None
      • and perhaps should have additional logic to verify geographic grid use-cases
        • Dimension standard names are latitude/longitude, and/or units == degrees
  • This will support multiple CRS per data file, use-cases not currently supported (required for SMAP and ICESat-2)