2004-05-31 Mon



Radar imagery recovers lost links in the Great Wall of China


China's famed Great Wall stretches some 3,000 kilometers (1,850 miles) between eastern China and the Himalayas. Built and rebuilt over hundreds of years, it served as the military frontier for a series of ancient Chinese dynasties. The color radar image at left shows a 50 km (30 mile) segment of the Great Wall in a desert region of north-central China (37.7 N, 107.5 E), about 700 km west of Beijing. The bright vertical orange line (passing through the box) is a portion of the Wall built during the Ming Dynasty (about 1350-1500 AD), which stands some 5-8 meters high.

中国举世闻名的长城自国土的东部一直延伸到喜马拉雅山系,跨度约3000公里(1850英里)。历经过去数百上千年的建造和重建,长城实际上已成为中国各个古老朝代的军事边界。左边的这张彩色雷达图片显示的是位于中国中北部沙漠地区(37.7 N, 107.5 E)的一段50公里(30英里)的长城,距离北京大约700公里。那条垂直的明亮的橙色直线(穿过图中方块)是修建于明代的一段长城(约公元1350年到1500年),墙体高度在5到8米之间。
[Fig.1: False color SIR-C image of Great Wall. (NASA/JPL image P-45924 ).]

Just right of the Ming wall is a much older remnant of the Great Wall dating from the Sui Dynasty at about 500 AD. Finding remains of the Sui Dynasty wall by spaceborne radar imagery is helping archaeologists to map a major cultural feature that has been buried by desert sands for generations.

Black and white enlarged NASA/JPL images at right, each about 3 by 2 km. in area, show two L-band views of the same square in the color image. The L-band (one of two, along with C-band, used by the Spaceborne Imaging Radar) provides relatively clear images of the two wall segments. Parallel to the wall are trees and orchards which appear as bright rectangles.These images, taken from the space shuttle Endeavour on April 10, 1994, also show towns and two shallow lakes used for salt extraction.


sting于 2004-05-31 11:48:54 发表在分类:分秒必整
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