A method is developed for locating gravel deposits in vegetated areas using six-band thermal imagery. The geologic history of the region is reviewed to select a potential area of study. An overflight is made using a six-band multispectral scanner. The data are displayed on a monitor and a spectral signature is selected from areas of known gravel deposits. A typical gravel signature demonstrates a strong absorption feature at the 9.2 Microm wavelength. The data are then processed with a computerized system and redisplayed to delineate additional areas in the scene with a similar spectral signature. Thedisplay is transferred to a map, and the signature areas are located in the field. Exploratory drilling is used to verify the presence of gravel and to determine the thickness and extent of the deposit. During 1989 and 1990, gravel deposits totaling 1 million cu m were discovered on national forest land near alexandria, louisiana, using this method. Concurrent studies are seeking to understand how the thermodynamic responses of materials contribute to the overall spectral radiant emittance in the thermal infrared spectrum. Ground instrumentation has been installed to support this effort. More time and effort are needed to advance the understanding of the physics of the method. The techniques developed can serve as a basis for further studies, directed towards extending the technology to a broad range of environments. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 2.
Abstract