Georeferencing: 3rd order polynomial transformation formula?

Discussion created by taowang on Feb 21, 2011
sorry for cross posting.

is there anyone who know the formula of polynomial transformation (1st, 2nd, 3rd order)
used in Georeferencing?
I just want to do some evaluating of the geo-registeration result.
for example, is the 2nd order polynomial as "a0 + a1 * x + a2 * x * x = y"?

thanks a lot.