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During our Investigations all the three different
apertures were used depending on the scale of aerial
photographs. Some aerial photographs were scanned using
both 50 and 100 micrometer aperture for the purpose of
comparison.
The scanning densitometer is connected to a magnetic
tape unit which records the densities of images in binary
form IBM compatible. Data recorded on magnetic tapes are
retrieved using an IBM 370 electronic computer.
The conversion of data to visible output requires the
use of computer programs. An optional program determines
the number of records and record lengths of a magnetic tape.
Another program converts binary data on a 9-track magnetic
tape, originally produced by the scanner, to IBM 370 com
patible binary halfwords on tape. Data recorded on this
tape can be used for matrix reduction (automatic count).
If print out of these data is required, a third program
has to be used.
Pattern Recognition
The procedure of automatic count is a difficult one.
First, density patterns of all possible images has to be
established. Then every uniform pattern detected on the
photos must be compared to the pre-established patterns,
sorted accordingly, and counted by the computer.
DATA ANALYSIS AND RESULTS
Large scale experimental aerial photography for Greater
Snow Geese, Eider ducks and diving ducks was carried out in
Eastern Canada and on the Bylot Island, N.W.T. Using the
obtained photographs color infrared transparencies of eider
ducks, and black and white pictures of Greater Snow Geese
and divers were digitized and density patterns were esta
blished. Preliminary result of this investigation was
reported in 1972 (1). Density patterns of several classes
within each species were recognized. However, actual class
identification was not possible due to lack of ground truths.
Since sufficient financial support was not available for de
tailed studies in subsequent years our investigation was
confined to the counting of the Greater Snow Geese as this
species represents simple image patterns on the photographs.
