Production of Index-derived Images
An urban area is a complex ecosystem composed of heterogeneous materials. Nevertheless, there are still some generalizing components among these materials. Ridd (1995) divided the urban ecosystem into three components, i.e., impervious surface material, green vegetation, and exposed soil while ignoring water surfaces. However, the open water is an important component of the urban surface and has to be taken into
consideration in this study. Accordingly, the urban land-use was grouped into the other three generalized categories, i.e., built-up land, vegetation, and open water (Figure 2). Based on these three elements, three indices, NDBI, SAVI, and MNDWI, were selected in this study to represent above three major land-use classes, respectively.