Essentially, I am lacking a number of coordinate systems necessary for multiple data sets that I am working with. I was wondering if there might be any library or archive online through which you can download more projections and coordinate systems?
I couldn't find any with Esri.
I have Arcmap 126.96.36.199 (something like that).coordinate systems data
Any help or suggestions are appreciated!
projectionsprojections and transformations
If you have EPSG well-known IDs for the coordinate systems--like 4326 = WGS84--you can type them into the search box.
If you have a list, you could post or email me and I can tell if they're available under a different name or in a later release.
mkennedy at esri dot com
There are an infinite number of coordinate systems that could be added, but only in the context of a finite number of known projections. Only Esri can add to the projection list (at least, if you wanted to deproject from it or project to it), but you could create a new CS string based on a known projection with alternate distance units or a custom prime meridian.
Each new release of ArcGIS has a Projection Engine update, so the easiest way to increase the probability of your coordsys being supported is to make sure you're using a recent build of ArcGIS