Spatial discrimination of salt-affected soil surfaces using landsat TM data - A preliminary study in the middle reaches of the Heihe river, China

A preliminary study has been conducted to test the effectiveness of the canonical discriminant approach to making spatial discrimination of salt-affected soil surfaces, using the Landsat TM data taken in the middle reaches of the Heihe River, China. A saline area can be considered a mixture of salt-affected patches which differ in degree, and hence we tried to make discrimination of salt-affected soil surfaces by canonical discriminant approach. Three 360×360 m test plots with different land surface conditions, "Bare-soil surface area (strongly saline), "Reed area (moderately saline), "Barley field (weakly saline)", were selected as training areas or groups. Five indices, B4 (band 4 DN), Wetness, SI, NDSI, and Fe₂O₃, (composite indices), were determined as discriminating variables, and two canonical discriminant functions, y ₁, and y₂, were obtained for the three groups using these five cUscriminating variables. When group centroids and individual cases were plotted on the plane made by two canonical discriminant functions, y ₁, and y₂, the groups of cases were quite distinct and their centroids were well separated, which suggest that the canonical discriminant approach is promising for spatial discrimination of salt-affected soil surfaces.