The use of reflected middle infrared and emitted thermal radiation in the remote sensing of soil water content

Abstract

Reflectance and temperature of bare field soil were measured to determine the relationship between soil water content and spectral reflectance and temperature. Reflectance in the six reflective Thematic Mapper (TM) wavebands plus a 1.15 to 1.30 μm waveband (referred to as MMR5) was measured using a ground-based radiometer across a soil water gradient provided by a line source sprinkler system. Temperature was measured using a hand-held infrared thermometer. The results of this study show that TM band 7 reflectance (2.05-2.30 μm) provided improved estimates of surface soil water content (0-0.5 cm depth) over estimates using reflectance information from all seven TM bands. Good correlations were found between band ratio spectral indices of TM5/TM7, MMR5/TM7, and MMR5/TM5 and surface soil water content. A soil temperature normalization utilizing daily values of maximum vapor pressure deficit was found to provide improved estimates of soil water content to depths greater than 0.5 cm over estimates using other temperature normalizations.