Improve support for geographic coordinates

[santisoler]

Description of the desired feature

Some functions from verde are intended to work with both projected and geographic coordinates.
Nevertheless, working with the latter imposes some requirements.
For example, one must ensure continuity around the globe: setting a grid between longitudes 170° and -170° or between 350° and 10° is not possible at the time because numerically the east coordinate is lower than the west one.
One way to fix this is to add a latlon=True argument to those functions in order to make clear that we are passing geographic coordinates.

I'll try to make a complete list of the functions that needs to be enhanced:

• inside()
• grid_coordinates()
• scatter_coordinates()
• profile_coordinates()
• get_region()
• pad_region()

Are you willing to help implement and maintain this feature? Yes

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[santisoler]

@leouieda Can you think more functions that need this enhancement?

[djhoese]

I'm not used to using verde functions directly (just a fan of the package and its interfaces), but I am dealing with similar issues in pyresample and the geoxarray library (geoxarray/geoxarray#6). I wonder if units could be specified instead of a boolean latlon keyword argument. Just an idea.

[snowman2]

The pyproj.CRS object has a is_geographic property that is likely useful.

[leouieda]

@djhoese I kind of wanted to avoid units in Verde because there are no restrictions on the actual data types that can be used. I like the idea but I don't know if it would be worth the effort of dealing with a unit library to replace the keyword. Are you planning on using that with geoxarray?

@snowman2 that's interesting but I'm not sure how we could use it. The functions above don't really take any CRS arguments right now. So we'd still have to add an argument and pass it around but instead of latlon=bool it would be crs=proj.CRS(...). We'll keep this in mind in case there is an added bonus to this, since it would also add a dependency on the pyproj API.

[leouieda]

@santisoler I think you could get started with a latlon or geographic style option in one of those functions.

[santisoler]

👍 I'll add a PR when I start tackling this.