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Remote sensing for resources development and environmental management
Damen, M. C. J.

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Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
Shuttle Imaging Radar (SIR-A) interpretation of the Kashgar region
in western Xinjiang, China
Dirk Werle
F.G.Bercha, Ontario, Ltd., RADARSATProject Office, Ottawa, Canada
ABSTRACT: The radar backscattering response of natural terrain in western Xinjiang and distinct man-made
features associated with land use and water resource management in the oasis of Kashgar is investigated using
SIR-A imagery. The brightness levels of the radar image signatures correlate well with the surface roughness
of various terrain units. Different backscattering effects of vegetation provide a detailed assessment of
cultivated areas and particularly forested windshelter belts, due to dominant volume scattering effects of the
tree canopy. The elaborate pattern of windshelter belts along the irrigation and drainage canal system, road
network and field boundaries serves as an excellent indicator for the classification of traditional cultivated
land, recent land reclamation areas and for the success of afforestation efforts. Spaceborne imaging radar
offers innovative mapping and monitoring capabilities with regard to regional terrain evaluation and land use
analysis in the arid regions of Central Asia.
In November 1981 the experimental Shuttle Imaging
Radar (SIR-A) system onboard the space shuttle
'Columbia' imaged approximately 10 million km 2 of
terrain including partial coverage of China.
Preliminary image analyses of arid environments have
shown that the radar view provides a new way to
examine problems of land reclamation, water
utilization, soil erosion and salinization (Cimino
and Elachi 1982) and terrain analysis (Woldai 1983).
Spaceborne Synthetic Aperture Radar (SAR) offers an
alternative imaging technique to optical satellite
sensor systems, the operational performance of which
is restricted by changing solar illumination and
atmospheric conditions. Data acquisition by optical
sensors is frequently limited by cloud coverage over
the area of interest. Radar which uses microwave
frequencies can obtain data regardless of cloud cover
or darkness.
Over the past decades, increasing population
pressure as well as political and strategic
considerations have led to further development of
marginal agricultural land in Xinjiang Province along
the western periphery of China (Weggel 1984). Remote
sensing, and LANDSAT image interpretation in
particular, has been applied in terrain analysis,
regional resource assessment, land use monitoring,
and for surveying and mapping purposes (Zhao 1984,
Zhao and Han 1981, Zhao and Xia 1984, Chu 1982,
Edelmann 1979).
A combination of geographical factors, i.e. the
position in the interior of the Asian continent and
the framing by high mountain ranges, have created
diverse environmental and physiographic conditions in
the Kashgar region. This has resulted in specific
adaptations of the cultural landscape in which the
oasis of Kashgar, once one of the important nodal
points along the ancient Silk Road, still commands a
prominent position as China's westernmost outpost in
Central Asia.
This study is an attempt to provide a synoptic
interpretation and an assessment of SIR-A imagery
with regard to physical and cultural landscape
features of the Kashgar region. Visual image inter
pretation methods were used in the identification of
terrain categories and forested windshelter belts.
This was followed by an examination of the regional
water supply and the associated spatial arrangements
of the oasis-agriculture.
The study area is defined by available SIR-A coverage
along data take 7 between 74°45'E and 76°45'E and is
approximately 9,000 km 2 in areal extent (Figure 1).
Over a distance of less than 70 kilometres, the
Kashgar region reveals a diversity of topographic
features and extreme climatic gradients and
hydrologic conditions. These factors determine the
relationship of the oases along the fringe of the
Taklimakan Desert in the Tarim Basin at 1,550 metres
to the surrounding glacier-topped mountain ranges of
the Pamirs with altitudes exceeding 7,500 metres.
Based on an integrated landscape approach, Zhao
(1984) classified terrain in western China into seven
categories, all of which may be found within the
study area: clay and silt level terrain, sandy level
terrain, stony gravel level terrain, denudational
mountain and hilly terrain, erosional high mountain
terrain, nival alpine terrain, and oasis (planted
The outstanding feature of the climatic conditions
in the western Tarim Basin is the exceptional
aridness. Kashgar receives less than 70 mm of
precipitation annually (Figure 2). The annual
temperature regime characterizes the climate as
cool-temperate. Westerly and north-westerly wind
Figure 1. Location map of the study area.