Looks slightly more complicated than this.
I've taken my Inverness satellite image as an example, which has:
A = -38610333, B = 300313394, C = 34548684, D = 19724088
To get the co-ordinates of LEFT (long), TOP (lat), RIGHT (long), and BOTTOM (lat):
TOP = (B+D)/60/60/1500
LEFT = A/60/60/1500
BOTTOM = B/60/60/1500
RIGHT = (A+C)/60/60/1500
And to go the other way, from map co-ordinates (in decimal degrees) to STL file, use:
Line 1 = LEFT*60*60*1500
Line 2 = BOTTOM*60*60*1500
Line 3 = (RIGHT-LEFT)*60*60*1500
Line 4 = (TOP-BOTTOM)*60*60*1500