Imaging and visualizing the spectral signatures from Landsat TM and 'τ' value-based surface soil microzonation mapping at and around Agartala (India)

摘要

This work aims to assess the soil microzonation of Agartala city and its surrounding areas based on spectral geophysical signatures. Different spectral resolutions of Landsat TM have been used for assessing the Normalized Difference Vegetative Index, spatial thermal emission representation and plant water moisture representation. Normalized Difference Vegetative Index (NDVI) was measured from band 4 (near-infrared (NIR)) and band 3 (photosynthetically active radiation (PAR)). The Digital Number (DN) values of thermal infrared band (TIR) were used for measuring spatial variation of thermal representation in the city area. A very simple model was developed for measuring thermal emission representative index from NDVI and automated classified TIR band. Overlaid NDVI and classified TIR shows the spatial distribution of thermal emission representative values. Classified mid-wave infrared band (MWIR) was used for measuring the surface geotherm units (τ) which are related with different types of soil. On the basis of spatial distribution of τ value which is clearly visible in a thermal emission representative map overlaid by classified MWIR, the soil microzonation map of the study area was prepared. This soil microzonation map shows that Agartala and its surrounding areas are characterized by four types of soil which are related to different geomorphic and geological units. The soil of this area is classified as dry sandy soil and sandy clay soil of the highland areas and wet sandy alluvium and clayey alluvium of the flood plain area.