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.

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。

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.

Landsat TM images were employed to characterize land-cover types and land-cover changes in Fuqing City and its adjacent areas in Fujian Province, southeast China. Three TM scenes from 1991, 1994 and 1996 were used to cover the city and the adjacent areas and a ®ve-year time period. Socio-economic data were also integrated with remotely sensed data for the study. Digital image processing with assistance of GIS has produced three classi®ed image maps. The comparison of the three maps reveals that the urban expansion was very rapid, a large number of arable lands have been lost, and deforestation has taken place in the study area during the ®ve study years. The main driving forces to the urbanization appeared to be the rapid economic development and trac infrastructure. The suggestion on the regional sustainable development for the county is also presented.

The normalized difference water index (NDWI) of McFeeters (1996) was modified by substitution of a middle infrared band such as Landsat TM band 5 for the near infrared band used in the NDWI. The modified NDWI (MNDWI) can enhance open water features while efficiently suppressing and even removing built-up land noise as well as vegetation and soil noise. The enhanced water information using the NDWI is often mixed with built-up land noise and the area of extracted water is thus overestimated. Accordingly, the MNDWI is more suitable for enhancing and extracting water information for a water region with a background dominated by built-up land areas because of its advantage in reducing and even removing built-up land noise over the NDWI.

城市建筑用地是一种复杂的土地利用类型, 在电磁波反射光谱上表现出明显的异质性。因此,很难用简单的方法将其从遥感影像中准确地提取出来。在详细研究了城市建筑用地的光谱特征以后, 创建了一种不直接采用影像的原始波段, 而是采用由它们衍生的3 个指数波段来构成新型建筑用地指数(IB I)。通过对ASTER 和Landsat ETM+两种多光谱影像进行的实验表明, 新指数除了能 够有效地增强影像中的建筑用地信息外, 还能和植被指数、水体指数一样, 用于进行数值运算, 从而 实现了建筑用地对城市生态环境影响的定量研究。对厦门、福州两城市的实例分析表明, 新的建筑 指数与地表温度呈正相关关系, 而与植被指数、水体指数呈负相关关系。研究进一步发现, 建筑指数 与地表温度的关系不是简单的线性关系, 而是一种指数函数关系, 说明高建筑用地比例地区的升温效应要明显高于低建筑用地比例地区, 因此, 对城市热岛的形成起着更大的作用。

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.

阐述了基于影像的Landsat TM/ ETM+ 的数据正规化技术及其发展。该技术通过将Landsat 影像的亮度值转换成传感器处的辐射值和反射率来对影像进行辐射校正。实例表明,使用正规化技术处理后的影像 可以明显削弱日照和大气的影响, 去除它们产生的噪声;其所求的传感器处的反射率与地面实测反射率的 RMS 值非常小

卫星遥感影像在接收的过程中由于受到许多因素的干扰, 使影像的质量受到一定程度的影响。而不同时相 的影像也会因为成像时光照和大气条件的不同而出现差异。因此, 在使用遥感影像之前往往需要进行必要的辐射校正。目前, 主要用于辐射校正的两种基于影像的正规化模型分别是Markham和Irish等人提出的校正日照差异的正规化模型(ICM) 和美国尤他州立大学遥感和地理信息系统实验室新近提出的日照大气综合校正模型(IACM/IACMt) 。本文以三对不同时相的Landsat TM/ETM +影像为例, 利用不变特征地物法求出各影像的相对噪音、RMSE和斜率, 并用这些指标来对模型进行定量对比和评价。结果表明, 当不同时相影像之间的季相、太阳天顶角和大气条件有较大差别时, 经过正规化处理的遥感影像的噪音和RMSE比未经正规化处理的影像得以明显降低,且斜率更接近于1, 镶嵌接缝淡化, 效果更好。但如果遥感影像之间的季相一致、成像时的太阳天顶角接近, 且影像晴空无云的话, 则经过正规化处理的影像和未经该处理的影像之间的区别并不大。就正规化模型之间的对比而言, 当影像无明显的大气影响时, ICM要好于IACM; 但当受到明显的大气影响时, 带有τ值的IACMt模型更好。