UnionDataset does not propagate .res

[jatentaki]

Description

TLDR: setting .res on UnionDataset should set it for all children.

A problematic scenario: assume a is a raster dataset with res=1 and b, c are vector datasets with res=0.0001. We want a union with res=1. If we write

ab = a | b
abc = ab | c

b will be cast to res of a and then c to resolution of ab -> all datasets have the same res=1. However if we write

bc = b | c
abc = a | bc

we will create bc with res=0.0001 and then cast it to the res of a. But since res is just a member variable of bc, it doesn't run any code to propagate down to b and c. When we query resulting abc we will get answers at differing resolutions, which in my case crashes the kernel with an attempt of rasterizing b and c at ridiculously high resolutions.

Steps to reproduce

I hope the analysis above is sufficient to understand the issue. I can provide a runnable repro if I am pointed to a way to reasonably generate fake data (I'm not sure how to do it best, such that the fake vector and raster datasets overlap and agree on metadata).

Version

torchgeo==0.4.1

[adamjstewart]

I'm able to reproduce this bug. I believe it affects both res and crs for both IntersectionDataset and UnionDataset. Working on a fix and better testing now.