96 PHOTO INTERPRETATION PICTURE, COLWELL
are used in concert. Figure 4 will serve to illustrate one of the many ways in which
multiband spectral reconnaissance is proving useful to the photo interpreter. Let us
PREDICTION OF PHOTOGRAPHIC TONES FROM SPECTRAL ANALYSIS
sol À LicHT REFLEGTANGE at EM C
z OF SURFAGE ^"^" 6RÁSS Z sol LIGHT SCATTERING BY
; E
= aol / 2 706 ATMOSPHERIC HAZE
& * eol
=
u 30 CEMENT =
o X
z ©
É 2 „SOLLE à
m «s PM N / dm 4 . 8
€ ad > NE ASPHALT| &
EA
‘0 1 1 1 1 2 EISE
400 500 600 700 800 900 à 900
-1.0
B ;
LIGHT SENSITIVITY E LIGHT TRANSMISSION
> / SUPER XX- AERO OF FILMS 8 BY FILTERS
= oo$+ PANCHROMATIC FILM x
E a!
= ;
= = WRATTEN 25A
ul $ (LIGHT REDFILTER)
oro o
> = WRATTEN 89A
d “INFRARED AERO FILM 2 (DEEP RED FILTER)
e OS
-2.0 à | : too I T OR ES
400 500 600 700 800 900 400 500 600 700 800 900
WAVE LENGTH, MILLIMICRONS WAVE LENGTH, - MILLIMICRONS
TYPE OF PREDICTED TONE ON POSITIVE PRINTS
SURFACE PAN - 25A INFRARED-89A
GRASS DARK LIGHT
CEMENT LIGHT LIGHT
ASPHALT DARK DARK
SOIL LIGHT DARK
MINFRARED-89A-
Fig.4. An illustration of the use of multiband spectral reconnaissance (two
or more film-filter combinations) to identify four surfaces which cannot be
identified on black-and-white photographs taken with just one film-filter
combination. For a discussion of the means by which the most suitable film-
filter combinations were selected, see text. (From article by Colwell, 1959.)
assume in this example that the objective is to distinguish consistently between four sur-
faces: grass, cement, asphalt, and soil. Each of these surfaces is sufficiently flat and
textureless so that we must rely primarily on photographic tone differences in order to
make the desired distinctions. As indicated in the four diagrams appearing at the top of