A Rmote Sensing Application On Urban Expansion And Heat Island Effect--A Study Case In Shaoxing, Zhejiang Province

With the rapid development of population and economic, urban expansion of big cities has been more and more obvious which seriously affected the surroundings. It is important to obtain urban expansion information and analyze the driving force of this expansion, especially for city construction and environment optimization. Additionally, with the development of urbanization, the intensity of heat island and the problems caused by heat island effect in big cities have been more and more serious and un-neglectful than ever before. It is necessary and useful for city planners and managers to detect rapidly and effectively the distribution of ground heat field and the factors of heat island, which is also significant for improving city environment.In this paper, we use image processing software, ERDAS IMAGINE8.5, and MapInfo to study urban expansion and its driving force in Shaoxing city, using two Landsat TM images of Shaoxing in 2003. First, we process the two TM images based on Erdas system, including geometric precision correction, image mosaic, and then extract the research area by subset image function. Comparing the results of supervised classification by maximum likelihood arithmetic and minimum distance arithmetic respectively, we think that the maximum likelihood arithmetic is more accurate. So we use this method to classify the urban town and get the urban boundary in 2003. Comparing the boundary in 2003 and 1992, we gain the urban area changes during the last twelve years. Analyzing the change characteristic and its driving force, we conclude that outskirts urbanized, suburbs outskirtied and country suburbanized. The results show that urban expansion is nearly related to the economic development, population increase and traffic establishment development.By means of advanced remote sensing techniques, we can dynamically monitor the ground heat field distribution over large areas. The key of RS techniques to monitor UHI(Urban Heat Island phenomenon)is retrieving LST from the thermal infrared data. In this paper, we mainly study the UHI of Shaoxing, Shangyu and Zhuji city, thereinto, LST were calculated by mono-window algorithm using TM6 data which was proposed by Tan Zhihao. And then we process the retrieval result to map the heat island effect and analyze the characteristics of the city heat field. In the end of this paper, the relationship between the urban expansion and the urban heat field distribution is analyzed to reveal the influence of human being activities to city environment. This study use TM6 data to get planetary brightness temperature(PBT) by PBTcomputing mode. Combining the atmospheric temperature and NDVI, we calculate the essential atmospheric parameters as atmospheric radiance, atmospheric effective mean temperature and atmospheric transmittance. After that, we use the mono-window algorithm to retrieve LST and reasonably process the result to get the final heat island effect image. The results suggest that areas with high land surface temperature conclude city zone and town center along the railway to north west and east. It also shows that there are low value points among the high value center and there are several small heat islands. The low value zone are mainly water body and greenbelt. So we consider that land cover affects directly the upper ground temperature and that heat island effection may be weakende through protecting the existing water body and increasing greenbelt of the city.Comparing the heat island map with the urban expansion map, we find that urban expansion is the main cause of increasing the new heat island.