The horizontal datum used is NAD27. The semi-major axis of the ellipsoid used is 6378206.4 meters. This is an alphanumeric combination of degrees north and west with a row column index applied to each 1 degree by 1 degree area. TILE - Row and column index to quadrangles. Illinois DNR designation.
Rows move north to south and columns west to east.
Quad T0101 is USGS 42091-E1. Values are in decimal degrees. Q15 - Indicates if arc is also a boundary for a 15 minute quad. 0 - arc is not a 15 min. 0 - arc is not a 7.5 min.