[Bug] - imod.prepare.reproject does not reproject to new grid size

[evaschoonderwoerd]

Bug description
When using imod.prepare.reproject to change to the cell size of another array, it does not regrid to the new cell size, but keeps the original cell size.
It seems to be an issue with rioxarray reproject_match as well, but xugrid - regridder does work fine.

Steps to reproduce

1. What error message do you get?
2. Can you create a minimum reproducible example?

rivsys = imod.idf.open(rivsyspad) <- dx, dy = 25.0
rivsys = rivsys.rio.write_crs('EPSG:28991')

bnd = imod.idf.open(bndpad) <- dx, dy = 100.0
bnd = bnd.rio.write_crs('EPSG:28991')

test = imod.prepare.reproject(bnd, like=rivsys) <- dx, dy = 100.0 (but should become 25.0)

Desktop (please complete the following information):

• OS: [e.g. Windows 11]
• iMOD Python Version 1.1.0
• Rioxarray version 0.23.0

[JoerivanEngelen]

Hi Eva,

Thanks for raising this issue. I think you are a bit confused on what reproject should do here:

reproject is used to reproject from one coordinate reference system (CRS) into another. E.g. "WGS_84" to "RD_new Amersfoort". This is not really to regrid to a grid with a different amount of cells.

To regrid to different grid sizes, you can use xugrid. The xugrid regridders also work with the structured grids. https://deltares.github.io/xugrid/examples/regridder_overview.html

This should probably do what you want to do:

import xugrid as xu

rivsys = imod.idf.open(rivsyspad) <- dx, dy = 25.0

bnd = imod.idf.open(bndpad) <- dx, dy = 100.0

test = xu.OverlapRegridder(source=rivsys, target=bnd, method="mode").regrid(rivsys)

I assumed here that rivsys is integer data, and therefore called the "mode" method. If is floating point, be sure to choose an appropriate method

[evaschoonderwoerd]

Hi Joeri,

Ah, its used to be possible with reproject, but good to know we should use xugrid for that and thanks for the example!

The user manual should be updated then, since there it is noted that reproject could be used to reproject into a new cellsize: https://deltares.github.io/imod-python/api/generated/prepare/imod.prepare.reproject.html#imod.prepare.reproject

(and if you update the manual, then please note that the given examples use 'imod.rasterio.reproject' instead of 'imod.prepare.reproject'

[JoerivanEngelen]

Ah, good to point that out. I think rasterio changed something here sometime, which causes this. It is probably good if we update the docstring warning that it is not fit for regridding and maybe add a warning when people provide a like.

Also note that we are considering to deprecate (and eventually remove) reproject, as rioxarray can take care of this functionality pretty much nowadays, see #282. (Removal would then be part of an eventual iMOD Python 2.0 release.)