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8 for
initial navigation to the photo strip and for additional details not dis-
cernible on the LANDSAT photos. The LANDSAT photos provided the primary
base for orienting the photo crew on each photo strip. Variations in
crop types, field boundaries, water courses, and terrain contours were
readily delineated. Roads, towns, and other man-made features were more
discernible on the contour maps. References were made of both sources
for photo flight line orientation.
Films and Filters
A primary consideration for classifying LANDSAT signatures in the three
types of vegetation (agriculture, range, and forest) was to detect
changes over the pixel area. Variation within these small l.l-acre areas
is generally the result of stress factors; i.e., soil, water, slope, fer-
tilization, etc. Considerable experience from many investigators has
shown the superiority of Aerochrome Infrared 2443 film (CIR) over
Aero-Negative film 2445 and Ektachrome MS Aerographic film 2448. This
background plus considerable firsthand experience in stress analysis of
forest and rangeland using CIR 2443 on various forest insect impact sur-
veys helped simplify the film selection for the Goose Lake Study.
Although a minus blue filter (Wratten 12) is usually recommended to be
used with CIR 2443, an orange filter (Wratten G-15) intensifies the range
of the red response. Further, the spectral response can be enhanced for
various types of foliar stress by adding combinations of CC filters (blue
and magenta). Tests of various CC blue and magenta filters for forest
defoliation evaluation indicated the 10 CC blue and 20 CC magenta plus
G-15 orange gave an excellent stress delineation. This combination
shifts the color balance slightly to the yellow-orange for a broad range
of damage intensity signatures on conifers and range plants. The filter
factor is increased about a half stop but is not significant if full
color saturation is desired. Light meter readings taken at different
flight altitudes (3,000 feet, 6,000 feet, and 8,000 feet) for different
vegeta- tive backgrounds were followed in exposing the CIR film in the
air.
