542 
It is based on the variation of surface emissivity due to 
the dielectric constant of liquid water that soil moisture 
can be sensed by the microwave radiometer. Just as the con 
clusions in the documents published earlier (9), the results 
of our experiment show good correlation between soil moisture 
content and measured brightness temperature. Pig. 5(a) is a 
digital image of the experimental farm of Jilin Agricultural 
University. Fig. 5(b) is a isothermal map of (a). It is 
clear that there is a low temperature region in the image, 
corresponding to a field with wheat stubbles, which had just 
been deeply ploughed.The ground truth shows that the soil 
type is black meadow soil. The moisture content of surface 
layer ( with a depth of 5 cm ) of bare wet soil is higher 
than that of the land with growing crops. 
(a) 
Avg. mois 
ture cont 
ent : 
wet soil: 
56.2% 
cropland: 
15.5% 
0>) 
Pig. 5, A digital image of the experimental farm of Jilin 
Agricultural Univ., at an altitude of 1000m acquired, 1979. 
As for microwave characteristics of vegetation, a detailed 
research report cannot be given here due to limitations of 
experimental conditions. But, KICRAD images show that vege 
tation exhibits characteristically high emissivity. Because 
of intensive scattering of the microwave energy by the foli 
age, the brightness temperatures of vegetation tend to be 
very warm and unpolarized. Comparing Fig. 2(b) with Fig.5(b), 
it turns out that the signatures of vegetations of marshland 
and dry field are different. One of the causes may be the 
difference of the equivalent content of water in the foliages. 
Coast Zone 
A number of images of coast zone with different geological 
structure were acquired during the flight testing over Jiao- 
zhou Bay. Analysis of these images show that the signature 
of coast zone is related to the topographical features, geo 
logical structure and moisture of surface layer. Fig. 6 is 
the image of a sandy coast zone located at Fengjajiang,Jiao- 
nan county. The corresponding relationship between the sig 
nature of this coast zone and the ground truth is listed in 
Table 2. In terms of the MICRAD images, the outlines of the 
intertidal zone are clearly discernible and the signatures