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Differing from optical remote sensing image, radar remote sensing image can be used to extract more useful information, and its application is becoming widespread in a variety of fields. Based on the central place theory, the spatial structure of urban system in the Northern China Plain is studied by using Radarsat ScanSAR mosaic image. The results show that: (1) Radarsat ScanSAR data are suitable for automatic extraction of building-up areas and has meaningful potential for urban geographic study. (2) The urban system in the Northern China Plain, which is deeply influenced by physical factors, especially hydrographic factors, can be divided into five categories: urban system of equal distance between central places on fluvial fan region at Mt.Taihangshan; hexagonal urban system in central part of Hebei flood plain; pentagonal urban system in the Yellow River fluvial fan; quadrilateral urban system in the vicinity of Huaihe River system; and scattered new towns in the places of rolling hills in central and southern areas of Shandong Province. (3) An evolution model of central place system from hexagon to pentagon and quadrangle influenced by river is suggested. (4) No matter hexagonal or pentagonal urban systems, this study has demonstrated that there are good relationship between the distance structure model of the central place and the real-life instance.

Suspended sediment is one of the most important parameters for water quality. Numerous experiential or deductive models have been advanced for detecting suspended sediment using remote sensing technology. However, due to the lack of atmospheric parameters and sufficient statistics, the precision or accuracy of these models cannot be guaranteed. In this paper, we take Lake Chaohu as an example area and process its TM/ETM+ data by applying the method of internal average relative reflectance for atmospheric correction and by extracting sediment information according to the value of SI (SI=(TM2+TM3)/(TM2/TM3)). The results show that: (1) an accurate extraction of water information of Lake Chaohu can be obtained by considering the relationship between the spectrums, (2) the data of relative suspended sediment revealed are in accordance with the instrumental data in situ, (3) the high-density suspended sediment area has expanded 1.5 times during the past 13 years, indicating changes of the lake's estuary, shoreline, and its suspended sediment content, and (4) the main sources of suspended sediment of Lake Chaohu are river transportation and erosion of the lakeshore.