Function to convert between coordinate systems

[foresthayes]

We should consider what coordinate systems we want to include support for or include as a default. It would also be useful to have a function to convert between systems. I often find myself converting back and forth between lat long and UTM. Generally I have found lat long the easiest to use for exporting location data (i.e. .gpx files) but most rasters are in UTM.

At a minimum this function should be able to:

1. Take a variety of input coordinate systems (at least UTM and lat long)]
2. Convert to a user specified coordinate system
3. Use user specified Coordinate Reference (CRS) or match an object

I have been using the sp package to accomplish this but I believe that it has been depreciated and largely replaced with sf so we should probably use that.

Thoughts on what the output should be? Should this replace the coordinate columns with the conversion, append the converted columns, or return a new object (of the input type) that only contains the new xy coordinates?

[Huh]

I like this idea. I think initially we should require lat/long decimal degrees WGS84. We can develop the initial bit from there and then build conversion wrappers later and add more bells and whistles. Sounds reasonable? Internally I don't want multiple CRSs to deal with...this will be in part an order of operations deal.

I am all for the sf package and do think it is the best bet going forward. I also really like gdal, but don't want to muddy the waters with external software.