be prepared to spend in the range of 300,000 for software and the time to 
learn how to use it.  By the nature of your question, it appears that you are 
unfamiliar with this task.  It would be better (both in time and cost) to 
send the photos out for processing.  

To pull elevations from aerial photos, you will need the negatives, the 
details of the lens through which the photos were taken and the actual spot 
elevations Typically, spot elevations are marked before the photos are taken 
(those white crosses on the ground), but you can do it after the fact.  this 
is generally done by a survyor.  You put all that data in the mapping 
software, combine with experience on just how the software works and you 
should come out with an orthotopo map.  

the class of software you need is called photogrammetric software.  the cheap 
end - but still good is DMS (desktop mapping system).  It is put out by the 
Univ of North(?) carolina and is maintained by graduate students.  It is 
fairly good and costs 2000 to 3000.  web address is www.rwel.com/dms.htm

a commercial package is available from KLT associates.  

www.kltassoc.com         I never asked what it cost, I imagine in the 20,000 
plus range.

good luck

s. figuers



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