This I can help with, since I've been there

The range-finding post is close to the edge of a 20 foot or so bluff overlooking the beach. The casemates with the guns are not situated directly at the edge of this bluff, however, and are instead placed about 1200 ft back from the beach in what would have been farm fields (and is mostly today). You can actually view the placement of the casemates in Google Maps.
http://maps.google.com/maps?f=q&hl=en&q=14400+Longues-sur-Mer,+Calvados,+Lower-Normandy,+France&ie=UTF8&cd=1&geocode=FaHK8AIdG1H1_w&split=0&sll=37.0625,-95.677068&sspn=23.875,57.630033&hq=&hnear=Longues-sur-Mer,+Calvados,+Lower-Normandy,+France&ll=49.344404,-0.691838&spn=0.009199,0.01929&t=h&z=16