A Fa x ud E 
  
(c) other land use categories selected were 
a 24. built up area 
: 25. water body 
26. irrigated bare field 
The mean and standard deviation of each individual 
field was calculated using the DIBIAS System. The results 
obtained from these studies are discussed here. 
ANALYSIS aND RISULTS 
WHEAT FIELD 
In all 21 individual wheat fields were studied for 
the analysis. Three wheat fields (3,%,7) with row 
direction South East and three wheat fields (2,6,7) with 
er North East row direction were selected for the studies 
related to influence of row direction. All the six fields 
were at the same look angle. Which were represented by 
similiar moisture conditions (varying 3.8% to 4.2% moisture 
content by weight) and crop conditions like crop height, 
density and row spacing and differ 3n row directions. 
Therefore, any chang» if observed on radar image can be 
attributed due to the influence of row direction only. 
Table 1 shows the observed mean and standard deviation for 
each of six fields. However, if one of the field size is 
large enough which is equivalent to the area of three  - 
individual fields (3,h5,5) with row direction South East. 
and the other field size is equivalent ta the total area 
of three field (2,6,7) with row direction North £ast, then 
mean gray values will be observed as 27.6 and 24,4 with 
standard deviations 16.5 and 14.3 respectively. This 
indicates that such differences can be observed on SLAR 
image if the sizes of field with different row directions 
are large enough. 
The second step of the study for the case of wheat 
field was to understand the influence of look angle. For 
this purpose, field number 9 to 23 (across the swath) 
corresponding to a variation of depression angle from 
44 to 14 degrees were selected. The mean radar return for 
wheat fields in across track direction is shown in 
Figure 3. It can be seen shat the sharp decline in gray 
values from look angle 19° to 14° are due to radiometric 
errors. 
To minimize the contributions due to errors the 
measured STC characteristics of SLAR-System can be used. 
However, an alternate method was developed in which each 
gray value was normalized with respect to mean 
a characteristics of land surfaces. Figure 3a shows the 
mean gray value across the swath obtained by the use of 
7000 scan lines. The gray values across the swath for 
wheat fields are normalized with respect to mean 
characteristics of land surfaces across the swath. 
245 
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