831 
OBSERVED FREQUENCY OF TONES 
>proach 
>n on the 
ita of 
-S document, 
; are 
r with a 
o 1000 DEGREE DAY IMAGE 
О 
: extent 
:he loss 
erpretation, 
approach 
l) of the 
t point, 
a hypo- 
presented 
sis of 
or this 
ned by 
own fields 
s of the 
Lcity, the 
L is a 
ough 
tructed. 
made to 
id on 
0 a 
1 data 
frequency 
Lght forward 
^y- 
sed to 
: always 
>tions. 
le day 
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lay" is a 
rowing 
FIGURE 1. Hypothetical distribution of photographic 
densities for 5 agricultural land-use classes on two image 
dates, typical of those found by measuring tone on ground 
truthed fields (known crop types) in the Great Plains 
region of the United States. 
OBSERVED PHOTOGRAPHIC DENSITY RANGES 
TONE LATE TONE LATE 
SPRING (1000 SUMMER (1000 
DEGREE-DAYS) DEGREE-DAYS) 
CROP TYPE 
MIN. 
MAX. 
MIN. 
MAX, 
Spring Wheat 
.34 
.48 
.12 
.26 
Oats 
M 
.39 
.20 
.32 
Barley 
.44 
.56 
.24 
.36 
Sod 
.59 
00 
.36 
.47 
Summer Fallow 
.76 
.86 
.77 
.95 
FIGURE 2. Tone descriptive data derived from observed 
tones of 5 crop types. Basically, this matrix is a 
direct reorganization of Figure 1 data.