Using active TIR imaging for ground cover identification and mapping

The authors report examples of the use of a scanning tunable CO ₂ laser lidar system in the 9-11 ym region to construct images of vegetation and rocks at ranges of up to 5 km from the instrument. Range information is combined with horizontal and vertical distances to yield an image with three spatial dimensions simultaneous with the classification of target type. Reflectance spectra in this region are sufficiently distinct to discriminate between several tree species, between trees and scrub vegetation, and between natural and artificial targets. Lidar sensing of vegetation offers some complementary characteristics to passive remote sensing. In the thermal infrared (8-12 μm), lidar interrogation of natural targets is essentially a pure reflectance measurement, unaffected by topographical shading and spatial variations in temperature. Differential measurements using CO₂ lasers have been known for some time to be useful in discriminating between vegetation types, tree species, and rock types. The authors have investigated the utility of a scanning CO₂ DIAL system in constructing vegetation maps for broad areas