A new index derived from existing indices – an index-based built-up index (IBI) –is proposed for the rapid extraction of built-up land features in satellite imagery. The IBI is distinguished from conventional indices by its first-time use of thematic index-derived bands to construct an index rather than by using original image bands. The three thematic indices used in constructing the IBI are the soil adjusted vegetation index (SAVI), the modified normalized difference water index (MNDWI) and the normalized difference built-up index (NDBI). Respectively, these represent the three major urban components of vegetation, water and built-up land. The new index has been verified using the Landsat ETM+ image of Fuzhou City in southeastern China. The result shows that the IBI can significantly enhance the built-up land feature while effectively suppressing background noise. A statistical analysis indicates that the IBI possesses a positive correlation with land surface temperature, but negative correlations with the NDVI and the MNDWI.

The fast urban expansion has led to replacement of natural vegetation-dominated land surfaces by various impervious materials. This has a significant impact on the environment due to modification of heat energy balance. Timely understanding of spatiotemporal information of impervious surface has become more urgent as conventional methods for estimating impervious surface are very limited. In response to this need, this paper proposes a new index, normalized difference impervious surface index (NDISI), for estimating impervious surface. The application of the index to the Landsat ETM image of Fuzhou City and the ASTER image of Xiamen City in China has shown that the new index can efficiently enhance and extract impervious surfaces from satellite imagery, and the normalized NDISI can represent the real percentage of impervious surface. The index was further used as an indicator to investigate the impact of impervious surface on urban heat environment by examination of its quantitative relationship with land surface temperature (LST), vegetation, and water using multivariate statistical analysis. The result reveals that impervious surface has a positive exponential relationship with LST rather than a simple linear one. This suggests that the areas with high percent impervious surface will accelerate LST rise and urban heat island development.

Urban spatial expansion in the Quanzhou region of southeastern China has been accelerated over the past 20 years. This has caused land cover changes and, thus, has significant impacts on the local ecosystem and climate. To study the urban expansion and heat island dynamics of the region over the past 20 years, multitemporal Landsat TM images of 1987, 1996, and 2006 were used. The estimation of the urban expansion was assisted by the index-based built-up index (IBI) through enhancing built-up land features in the images. The urban-heat-island (UHI) effect was assessed using the urban-heat-island ratio index (URI). Multitemporal analysis indicates that the great increase in urban area has resulted in the development of UHIs in the region. Regression statistics reveal that built-up land has a positive exponential relationship with land surface temperature (LST). Therefore, the increase in built-up land percentage can exponentially accelerate the rise of LST.

城市空间的快速扩展已使得原来以植被为主的自然景观逐渐被人工不透水建筑物所取代，并对区域乃至全球的生态系统造成了明显的影响。因此，准确了解城市不透水面及其与植被、水体、城市热环境的相关关系对于城市的科学规划和城市生态系统的修复具有重要的意义。以福州市为例，采用遥感空间信息技术，获得了城市不透水面、地表温度、植被和水体的信息，并对它们的关系进行了定量分析。发现了城市不透水面与地表温度之间的关系并不是一种简单的线性关系，而是一种很显著的指数函数关系，说明高不透水面比例地区的升温效应要明显高于低不透水面比例地区。多元统计分析表明不透水面是引发城市热岛的最重要因子。