Landsat-7 ETM+与ASTER建筑指数的定量比较

Quantitative comparison of Landsat 7 and ASTER multispectral measurements for the NDBI and IBI

城市化进程导致的城市建筑用地急剧扩张已对全球的环境资源产生了负面影响,因此亟需对其进行监测。在中尺度卫星对地观测系统中,Landsat和ASTER数据最适合于监测城市建筑用地变化。但是迄今为止,这两种传感器数据的建筑指数之间的关系并不清楚。因此,利用三对同日过空的ETM+和ASTER影像来查明二者建筑指数(IBI、NDBI)之间的定量关系,通过回归统计分析来求出两种传感器建筑指数之间的转换方程。结果表明,ETM+和ASTER的建筑指数既有相似性,也存在着明显的差异,ASTER反演的建筑指数均值可大于ETM+达48.6%,因此二者在实际应用中不宜直接进行对比,而应通过转换方程进行转换后才能对比。分析表明,两种传感器建筑指数之间的差异是二者在NIR和SWIR波段之间的光谱差异造成的。

Accompanying with accelerated urbanization processes,urban built-up lands have expanded dramatically and caused negative impacts on environments and natural resources of the world.Thus,there is an increasing need to monitor the dynamics of the urban built-up lands.Of the medium-scale earth observation systems,Landsat and ASTER systems are most suitable for this monitoring task.Nevertheless,the relationship between the built-up indices of the two sensors has not yet been revealed so far.To quantitatively investigate this relationship,this study crossly compares the NDBI and IBI built-up indices of Landsat-7 ETM＋ and ASTER sensors based on three tandem image pairs.Regression analysis was used to examine the quantitative relationship through the scatter plots of the built-up index values of the two sensors.This yielded the models for the conversion between two sensors＇ built-up indices.Results indicate that there are differences in the compared built-up indices between two sensors in spite of a high degree of correlation between them.The values of the built-up indices of ASTER are greater than those of ETM ＋ by 48.6% in NDBI or 37.5% in IBI.Accordingly,the built-up index information derived from ASTER data cannot be compared directly with those derived from ETM＋ data in the applications.A conversion between them using the conversion models obtained in this study is recommended.Detailed spectral analysis reveals that the differences in band wavelengths and spectral response functions of the near infrared and shortwave infrared bands between the ETM ＋ and ASTER sensors contribute to the built-up index difference between the two sensors.This is because the NDBI and IBI are composed merely or mostly by these two bands.