• NAD27 is disabled.
• If the data is in feet, you must pick the units first. You will have to read the metadata with your imagery.
• You can pick the state by typing in the two character abbreviation. If the state has a single SPCS zone, it will automatically be selected. If the state has multiple zones, you will be directed to select the correct zone. If you choose one of the three states with both TM and LCC zones, you will be asked which type you want.
• You can alternatively select the type of SPCS projection, and then select the correct zone from all those using that type of projection.

This uses two files for the constants.