NASA/JPL contract No. 960983: 1997-2000

Identification and Mapping of Expansive Clay Soils in the Western US: Using Field Spectrometry and AVIRIS Data

Field/Laboratory Work

The laboratory work (mineralogical composition from XRD analyses and swelling potential determination with standard engineering tests) has been done over the ~180 field samples that we collected in 1997 and 1998 along the Urban Corridor from Canon City/ Pueblo to North Boulder. The correlation between the spectral features, mineralogy, and degree of swelling on those known samples would allow us to develop a model to be able to predict on others samples the "unknowns" (mineralogy, swelling potential) from the spectral signature (Olsen et al., 2000; Chabrillat et al., 2001, in revision; Goetz et al., 2001, in press).

Remote Hyperspectral Data

AVIRIS high altitude images were acquired over the Urban Corridor in Colorado in 1997 (USGS data), 1998 and 1999 (this proposal). We also got low altitude hyperspectral images from AVIRIS in 1998 and HyMap/AIG in 1999. During each overflight we were in the field with portable spectrometers to acquire spectral measurements on calibration target on the ground. We focused our results on several images selected over the most promising areas in terms of amount and quality of exposures of expansive clays. Swelling soils outcrops are usually covered with sparsely dry vegetation. Pre-processing and calibration of the data to reflectance was done using atmospheric modeling (ATREM) and field spectra. Then principal component analyses (MNF) and multiple unmixing techniques such as the Mixture Tuned Matched Filtering (MTMF) were used to separate the mineralogic signature from the others contributions in the pixels (vegetation, buildings, roads, etc...). The results on detection and mapping of swelling clay soils with AVIRIS and HyMap data have been published in several papers: Chabrillat et al., 1999; Chabrillat et al., 2000; Chabrillat et al., 2001, submitted. The comparison of AVIRIS high and low altitude data was reported in Chabrillat and Goetz, 1999.