EE EIE 
Figure 3b shows the uncorrected and corrected gray values 
for wheat fields. It can be seen that the wheat fields are 
uniformly represented across the swath. This technique is 
found to be suitable for correcting these errors. Authors 
are extending this technique for the calibration of SLAR 
images. 
OTHER LAND USE CATEGORIE 
Three stubble fields (1A4,13,8) were investigated 
individually. These fields are located at a depression 
angle of 22 degrees. It has been observed that within the 
same land use category of stubble field the range of 
variation of gray value occurs between 10.2 to 15.0 and co- 
rresponding standard deviation from 8.2 to 10.9. Conside- 
ring that all the three fields produced the same radar 
return, an unique representation of these fields can be 
assigned with mean gray value at 13.1 and standard 
deviation as 10. They are easily distinguished in an 
enviornment surrounded by young wheat field as can be seen 
on SLAR image in Figure 2. 
The grass field (A) reflected high with mean gray 
value at 30 and standard deviation at 7.1. The field can 
be identified on a SLAR image when surrounded by wheat 
field. 
The observed mean gray value for irpigated bare field 
(26) located at a depression angle of 30” degrees was 
around 34. The soil moisture in this field was 14.1% by 
weight. It may be noted that wetland area near the 
waterbody is also represented by the same grey values. 
WATER BODY AND BUILT UP AREA 
The water body (25) which lies at a depression angle 
of 40 degrees was readily recognized on the SLAR image. 
Since the study area was relatively flat, it was easy to 
recognize the water body however for the areas with relief, 
the detection of water body poses a problem. 
The bright return on SLAR image at depression angle of 
40° was most easily recognized as the village, Rethal. The 
mean return of highly concentrated built up area was obser- 
ved at 43 with standard deviation at 9.6. The roads which 
were parallel to flight path were also detectable even at 
a far range inspite of poor image quality at far range. 
OVERVIEW 
In the process of study of each individual field, 
one can have an overall idea of digital data as represen- 
ted by different land use categories. It was noted that 
higher is the mean value, the value of standard deviation 
was also high. This shows that multiplicative nature of 
noise level exists in the image. Therefore, normal image 
enhancement technique should be applied carefully. A 
comparative study of the enhancement technique has been 
studied by the authors /76 7. 
246 
50- 
40 
30 
20 
10