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3 - MAIN CHARACTERISTICS OF THE SELECTED RADIOMETRIC CALIBRATION TEST SITES 
IN CHINA 
3.1. Geographic environment and optical characteristics 
Germo west Gobi : its geographical coordinates are : N 36°2r, E 94°33'. It has an area of 100 km^ and its 
altitude is 2830 m above sea level. The ground surface is composed of Pleistocene sandy conglomerate without 
any vegetation. The surface is quite flat with a 1% mean slope. The conglomerate is scattered evenly. The 
diameter of particulate ranges between 2 and 20 mm. They are mainly composed of andesite and dark gabbro. 
Under the effect of wind erosion it forms a relatively hard conglomerate sandstone shell. The mean reflectance 
spectrum (16 samples) of this test site is given in Figure 1. 
Wavelength (nm) 
Figure 1: Mean reflectance spectrum of Gobi in Germo test site. 
Dunhuang area : Dunhuang is a world known cultural city on the silk road of China. It is now a famous sight 
seeing spot for its historical culture. In the north west part of Dunhuang there is the alluvial Fan Gobi. Its 
geographical coordinates are N 40°22', E 94°30'. Its total area is 60 x 40 km^ and the flat and leveled area is 
30 x 40 km^. The altitude is 1183 m and the terrain slope ranges between 1.5% and 1.0%. The surface is 
mainly composed of fine sand and conglomerate sandstone. Its mineral composition is a mixture of gneiss, 
limestone, quartzite, diorite and granite. The diameter of particles ranges between 10 and 20 mm and the 
surface is without any vegetation. The mean reflectance spectrum (16 samples) of this area is given in figure 2. 
Figure 2 : Mean reflectance spectrum of Gobi in Dunhuang test site.