earth satellite thematic sensing

(Data West Research Agency definition: see GIS glossary.) Landsat satellites have a Thematic-Mapper (tm) sensor that produces images in many spectral regions, e.g., in the visible range, in the near-infrared, in the mid-infrared, and in the thermal infrared. The visible and near-infrared regions provide information on water turbidity, bathymetry, currents, and sediment plumes. (Water containing large quantities of suspended sediment has a higher reflectance than clear water and can be easily separated using satellite data). The near-infrared band is used for vegetation mapping since it distinguishes features by variations in plant cell structure. Mid-infrared spectral regions reveal plant water content and help delineate vegetation type. Two mid-infrared bands are used for geological studies and one for collecting imagery at night and identifying hot objects, such as forest fires, lava flows, emissions from smoke stacks, new construction, and soil use.