Abstract
This paper proposes a technique to extract urban built-up
land features from Landsat Thematic Mapper (TM) and
Enhanced Thematic Mapper Plus (ETM) imagery taking two
cities in southeastern China as examples. The study selected
three indices, Normalized Difference Built-up Index (NDBI),
Modified Normalized Difference Water Index (MNDWI), and
Soil Adjusted Vegetation Index (SAVI) to represent three
major urban land-use classes, built-up land, open water
body, and vegetation, respectively. Consequently, the seven
bands of an original Landsat image were reduced into three
thematic-oriented bands derived from above indices. The
three new bands were then combined to compose a new
image. This considerably reduced data correlation and
redundancy between original multispectral bands, and thus
significantly avoided the spectral confusion of the above
three land-use classes. As a result, the spectral signatures of
the three urban land-use classes are more distinguishable in
the new composite image than in the original seven-band
image as the spectral clusters of the classes are well separated.
Through a supervised classification, a principal
components analysis, or a logic calculation on the new
image, the urban built-up lands were finally extracted with
overall accuracy ranging from 91.5 to 98.5 percent. Therefore,
the technique is effective and reliable. In addition, the
advantages of SAVI over NDVI and MNDWI over NDWI in the
urban study are also discussed in this paper.