6 PHOTOGRAMMETRIC ENGINEERING
task of counting thousands of waterfowl on aerial photographs is in itself ex-
acting and tedious.
Kalmbach (1949) constructed a scanning device to facilitate the counting
of large numbers of waterfowl on aerial photographs. The device is fully de-
scribed and illustrated in The Journal of Wildlife Management, 13(2): 226-227.
Suffice it to say here that it has the over-all appearance of a shallow box ap-
proximately 13 inches by 11 inches by 2% inches in dimensions with a hinged
Fic. 2. Aerial photography facilitates the censusing of such animals as these Harbor Seal along
the Bering Sea Coast. The seals come to rest on this small island formed at low tide.—E. P. Had-
don, Fish and Wildlife Service.
lid made of 28-gage brass. A slot in the lid with the same curvature as that of
the route of an 8-power binocular microscope mounted at the end of an arm
pivoted on a standard to the right of the device permits minute examination of a
portion of the photographs at a time. After such a strip has been examined, a
lever is pressed which shifts the photo to one side just the width of the scanning
slot, thus removing the old and presenting a new and contiguous field for in-
spection.
Photographs may also be “blocked off” for ease in counting waterfowl by
