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