The best answer I've found to this question is non-technical: find out where your data came from. Agencies and organizations tend to be consistent with their use of projections. Know it came from your state DOT? Look at the rest of their data and see what it tells you. Don't know where it came from? An educated guess is just as likely to send you down the right road.

At least it makes tackling the problem with brute force a little more do-able.

The best answer I've found to this question is non-technical: find out where your data came from. Agencies and organizations tend to be consistent with their use of projections. Know it came from your state DOT? Look at the rest of their data and see what it tells you. Don't know where it came from? An educated guess is just as likely to send you down the right road.

At least it makes tackling the problem with brute force a little more do-able!