Support for miles

[rpungello]

Just wondering if there's a reason miles aren't a supported length unit. While I understand most of the world uses kilometers instead, there are some very obscure length units that are supported, so it seems reasonable that miles (statute and nautical) should be supported as well.

I can work on a PR if this is something that would be added, but before doing so I figured I'd check if there was a reason they're not currently supported.

[rpungello]

To add to this, miles appear to be included on epsg.io, which so far as I can tell is the basis for the units that are included.

https://epsg.io/?q=kind%3ALENUNIT+mile

[dvdoug]

The reason is simply that out of the thousands and thousands of different CRSs in the EPSG database and the thousands and thousands of conversions between them, nothing actually use miles (whether statute, nautical or US Survey) so it would just be an orphaned unit without a purpose. Kilometres if I remember correctly is actually used by a single CRS, otherwise it would be missing too.

If you've got a custom CRS that needs support for miles I'd be happy to add it but not for "just because" reasons because the filesize of this package is already very large, and every kilobyte adds up 😞

[rpungello]

Ah, appreciate the explanation. I was more focusing on the ability of this package to measure distance between two geographic points, where it would be helpful to be able to get that result in miles (for displaying and filtering by "nearby" objects) using the native functionality of the package.

So not exactly an "orphaned unit without a purpose", just one without a "built-in" purpose. However, as one of the stated uses of the package (in the main blurb) is calculating distance between points, I'd argue the ability to report that distance in what's probably the second most popular unit for measuring geographic distance is a reasonable feature to have.

I have a PR ready to go (well, mostly ready, still waiting on some of the tests to finish up).