A compound method for automatically extracting plateau wetlands from satellite imagery

Abstract

Timely information on wetland distribution can be effectively acquired by means of remote sensing. A Landsat TM image recorded on 17 July 2009 (row: 36; column: 134) at a spatial resolution of 30 m was used to map wetlands in Maduo County of northwestern Qinghai Province with a combined method of thresholding, tassled cap transformation and vegetation indexing. The wetlands found in the study area fall into two broad types, I and II. Type I wetlands are characterized by a close proximity to water bodies. Type II wetlands are characterized by a higher vegetative component that obscures their morphology. Thresholding was used to map type I wetlands from TM5. Tasseled Cap transformation was used to map type II wetlands. With the assistance of NDVI, snow was then removed, leaving only grassland and type II wetland to be separate. Type 1 wetland was mapped at 832 km². The second type of wetland was mapped at 422.97 km². A total of 1254.97 km² wetlands were mapped. Comparison with the raw color composite of the same image reveals that the mapping has been accomplished quite accuracy. More research will be undertaken to compare the classified results with those obtained with supervised and unsupervised results. Both thresholding and Tassled cap transformation are found to be effective at detecting different types of wetlands in the plateau environment