Dan Mouers comments are quite to the point: it is often very, very difficult
to obtain substantial funding until an important find has been made.  I
nonetheless believe that cartographic evidence can be very useful and quite
complete: the problem is interpreting what is illustrated and what it's actual
importance may be.  May I suggest that you consult the current issue of the
magazine "Microstation World" by Bently Industries for an article on our use
of GIS systems and  image-correction software for developing databases from
cartographic soureces in Quebec City.
 
William Moss
City Archaeologist
Quebec City