Study On Temporal And Spatial Evolution Of Urban Pattern Based On SAR Images

Beijing, the capital of our great country, is one of metropolis in the world. The velocity of urbanization is very rapid since 1990'. The urbanization has brought a series of problems such as environment deterioration, aerial land reduction and so on. And the urban pattern is changed with the urbanization.A means for a better understanding of urban areas is remote sensing techniques. Satellite imagery can significantly improve the monitoring of cities in a wide range of applications, e.g., the detection of urban changing, mapping road and streets, mapping urban demarcation, and mapping the urban pattern.Nevertheless the number of studies using SAR data is much less than that using optical ones notably concerning investigation on urban areas, though the studies for detecting built-up area as man-made features. In addition, radar imagery may provide the third dimensional information. Hence, SAR imaging technique is relevant tools to analyze urban land use patterns.The automated production of maps of human settlement from recent satellite images is essential to detailed studies of urbanization, population movement, and the like. Optical satellite remote sensing depends on sunlight illuminating the Earth in order to obtain useful images. Its performance is therefore restricted by the presence of clouds, fog, smoke or darkness. On the contrary, a SAR system can operate at day and night regardless of cloud cover and weather conditions. Furthermore, the SAR imaging system will show the microwave backscattering properties of ground surface covers and manmade structures. Settlements are especially sensitive to radar microwaves due to the presence and effects of horizontal and vertical structures (dihedral and trihedral reflectors). The geometric arrangement of settlements, the shapes and sizes of structures, and the morphology of settlements create high contrasts between human settlements and natural terrain and surface features because of an abundance of unique dihedral and trihedral reflectors and patterns ideally susceptible to radar sensors and radar analysis in an urban environment.