I've obtained solar radiation data in an Ascii format and have been able to create a rastor in arcmap, but my issue is with the projection. I have specific sites that I want to extract radation data for. Anyways, the header of the ascii file contains x/y centers, but the company says I can use the data in any projection I want...I'm not sure how to do this. Do I need to change the values in the header (as of now its not supposed to have any spatial reference "undefined" but there are values in it) and if so how do I know what values to put in???? For exapmle XY coordinates of my ascii are roughly 110,-43 and the actual xy values should be around 6000000,400000.