New Xarray accessor for rasters through GeoUtils

Hi all,

(Co-opening in rioxarray due to the raster nature of the accessor: https://github.com/corteva/rioxarray/issues/687)

As in https://github.com/pydata/xarray/issues/8040 for DEMs, writing an issue to let you know that we intend to write an Xarray accessor to enable functions specific to raster analysis in our package GeoUtils. GeoUtils is built on top of rasterio and aims to facilitate raster/vector manipulation.

To answer the question you'll probably ask: Why the need for another raster accessor when there is rioxarray and xarray-spatial?
In short:

• For rioxarray and georeferencing: we simplify the handling of georeferenced data of rasterio/rioxarray for end-users focusing on analysis by allowing match-operations between any raster/vector and for all types of functions (reproject, crop, rasterize, polygonize, etc), and reading the metadata of each object for them to work implicitly in any CRS. Done separately, those can be a complex learning curve for beginners, and lead to inconsistent results for these "basic operations" in the community.
• For xarray-spatial and analysis tools: we simply want to add a lot more functionalities that (1) understand georeferencing, (2) are robust to nodata and (3) pixel interpretation of rasters (corner or center?). In particular: local and zonal stats, variography, 2D registration, filters, grid interpolation, error propagation, etc... We'd wrap functionalities existing in the non-GIS xarray ecosystem whenever we can, and adapt them to georeferenced ops. Those can be tricky to adapt due to the above 3 points, and so we really feel the need for them to be implemented & tested consistently somewhere. We'd build on top of xarray-spatial for what exists there, and try to coordinate! 😊

The accessor would mirror all the functionalities we have (and future ones) and build them on top of rioxarray and geocube. Those are:

• Match-reference georeferencing manipulation (a reference = another xarray.Dataset or a geopandas.GeoDataFrame, when using reproject, crop, rasterize, polygonize to allow implicit metadata handling and facilitate quick analysis),
• Support for spatial georeferenced operations with nodata values, such as proximity (I see a bit of overlap with Xarray-Spatial/Proximity: https://xarray-spatial.org/user_guide/surface.html),
• 2D registration for georeferenced data,
• Spatial statistics for georeferenced data,
• Error propagation for georeferenced data,
• Filters for georeferenced data,
• Parsing sensor metadata from filenames/auxiliary data for most common satellite data (might evolve in a different package in time!).

For the accessor name, I was thinking of "geo" or "gu", such as: ds.geo.polygonize(), ds.geo.proximity(), ds.geo.coregister(). I'm not sure if those are already in use. What do you think?

Thanks!

Read this proposal with the linked xarray issue 8040 and rioxarray issue 687, then review the GeoUtils, rioxarray, geocube, and xarray-spatial projects named in the issue. No files, tests, or implementation entry points are identified; done would require an agreed accessor name, scope, and implementation plan for the proposed raster-analysis functionality.