Remote sensing has been widely applied for soil moisture estimation. However, such estimates become difficult to obtain and can be inaccurate when applied to complex earth surfaces with more than one soil type because of the interference of spectral signals from different soil components. This study aims to develop a moisture prediction method that is insensitive to soil types; this is based on in situ samples collected from an intertidal zone in Jiangsu Province in China and on laboratory measurements of soil spectra. The results demonstrate that for a reflectance-based method, moisture content is closely related to reflectance on the three wavebands centered at 2143, 1760, and 742 nm for four types of soil (sand, silty sand, sandy silt, and silt) considered separately; the relationship is not close if all soil types are mixed together (R 2 =0.77 ). To develop the desired model, a linear spectral mixture model (LSMM) was employed to extract parameter water abundance (Wa: information on soil water content) in advance, while eliminating redundant information from other soil components. Wa has a relatively higher correlation (R 2 =0.82 ) than reflectance with moisture content for a mixed soil type. Thus, employing the LSMM helps realize a practical water content estimation model for predicting moisture over complex earth surfaces, because it has the potential of eliminating spectral effects from soil components.
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
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