Fixes #957.

This PR should get rid of almost all warnings when running unit tests, except from the one that seems to come from geopandas internals.

I initially read a few things on the geographic coordinate systems to understand the problem, and then tried to convert the resulting geodataframes to a different CRS. But that turned out to be a bad idea, because we actually want to actual dataframes in EPSG:4326, thus I reverted to just ignoring the user warnings in the test code.

PR checklist:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)