FWHM (1900nm) <= lOOnm 
0. 7 > Pband (220Onm) > 0. 3 
I Hit: Pband (2200nm) =1.0 
slop (1900nm) > -0. 5 
or Asy (2200nm) <= 1. 0 
Vermiculite: Pband (1900nm) =1.0 
Asy (1900nm) < -1.0 
FWHM (1900nm) >= lOOnm 
Pband (2200nm) < 0. 3 
Pband (2300nm) > 0. 3 
4). Study on Microwave Remote Sensing 
a. Measurement of Dielectric Constant and Its Role in SAR Data Analysis 
Due to chemical and physical varieties, the dielectric constants of different rocks and 
minerals are different; which will make contributions to radar back-scattering. What is more, 
the roughness of land surface is determined mainly by rock types, as well as weathering and 
erosion processes. As a result, lithologic units could be delineated using SAR data. In the 
inner Mongolia, a gold-bearing structural belt was detected on SAR imagery. 
Assuming the SAR system parameters and roughness and chemical composition of soils remain the 
same as time changed, the main factor determining radar backscattering of soil is the moisture 
contents. Hence, SAR data are used successfully in soil moisture monitoring. 
b. Study on Radar Signal Penetration 
In the test site of Inner Mongolia, SAR penetration has been examined by SIR-A data. The test 
site consists of base rock of Precambrian metamorphic rocks and Mesozoic granitoids, covered by 
about lm thick sand sheet.On SIR-A image the structure of basement rock could be seen clearly, 
which would not be found on MSS images. This phenomenon could be explained by Elachi’s radar 
scatteriing mode 1. The dry sand sheet is a low-attenuntion layer. SAR signals penetrate this 
layer and are reflected from basement. 
c. Optimum Radar Depression Angles Selection for Geologic Analysis 
In order to obtain maximum geologic information on SAR data, radar depression angle should be 
selected according to geologic/geomorphic unit’s charac ter i s t ics. The main purpose is to limit 
the side-effect of overlay and shadow to their minimum. Slope angle and relative altitude are 
two of the fundamental factors affecting overlay and shadow on SAR images. Based on 1: 1 000 
000 scale DEM of China and associated data, the topographic units are classified, and related 
radar depression angle ranges are determined. Finally, the Optimum Radar Depression Angle Map 
of China was proposed, which could be the preliminary guide to SAR campaign in China. 
d. THE STUDY OF THE MICROWAVE REMOTE SENSING OF SOIL MOISTURE 
At microwave wavelength the dielectric constant of water is approximately 80 compared with 3 
to 5 for dry soils. Therefore, as the moisture content of a soil increases its dielectric 
constant can reach values of 20 or more. As a result the microwave energies from soil are 
strong functions of its moisture content. 
The relation between microwave backscattering coefficients and soil moisture plays an 
important role in the active remote sensing of soil moisture. In the past only a empirical 
model can be used, which is purely dependent on experiment results and is not suitful for 
general case. At present a new physical model for the relation between backscatter ing 
coefficients and soil moisture,which is based on an understanding of the physics of the 
microwave-target interaction, has been established by using rough surface scattering theory 
and dielectric constant model. The effects of sensor parameters ( frequency, polarization, 
and incident angle), surface roughness, and soil texture, etc. on this relation have been 
considered. The good agreements between theoretical and experimetal data verify the 
efficiency of the model. Finally the new model is used to analyse the SAR image so that the 
distribution of soil moisture can be obtained. 
Recently the scatterometer measurements as a fundmental experimental research have been 
conducted by using L and X band truck-mounted scatterometers. The results are analysed to 
provide the dependence of the backscattering coefficients on soil moisture, incident angle, and 
polarization for different frequence and roughness.