Evaluation of Thematic Mapper for Detecting Soil Properties Under Grassland Vegetation

Analysis of Thematic Mapper data acquired November 15, 1982, over a vegetated site located in the East Texas Timberlands and Claypan area of Texas has indicated that montmorillonitic clay textured soils can be separated from soils with different textures. The difference of TM band 4 (0.76-0.90 μm) and band 7 (2.08-2.35 μm) had an agreement of 55.8 percent with the USDA soil survey for upland clay soils. This compared to 55.9-percent agreement when all six bands (excluding the thermal) were used. The disagreement occurred at the boundary lines as defined by the USDA soil survey and the spectral data. This result is considered to be fairly good considering the difficulty in placement of soil boundaries by the soil scientist in the field. While the exact influence on the vegetation and thus the spectral response observed by TM is not understood at this time, it appears that TM band 7 is responding to the type of mineralogy of the soil and that soil properties important to the plant can be detected using TM.