Remote Sensing Retrieval of Substrate Bearing Strength from Hyperspectral Imagery at the Virginia Coast Reserve (VCR'07) Multi-Sensor Campaign

NRL Hyperspectral Imagery Trafficability Tool (HITT): Software andSpectral-Geotechnical Look-up Tables for Estimation and Mapping of Soil Bearing Strength from Hyperspectral Imagery

“…Note that other matching algorithms could potentially be applied here, for example, ENVI's "spectral angle mapper" (Kruse et al, 1993); however, the use of direct spectral distance, as is done in our match_spectra.pro software, may be preferred for a number of reasons. One of the factors outlined by us in Bachmann, Nichols et al, 2010f, 2009, 2008a, as being significant to the estimated retrieval of bearing strength is soil moisture, which directly affects overall albedo, as well as spectral shape. Thus, the absolute value of the reflectance values, not just spectral shape, is actually relevant to the retrieval process.…”

“…Surface moisture level and composition are relatively easy to retrieve from hyperspectral remote sensing; grain size is more difficult, but still feasible (Bachmann, Nichols et al, 2010f, 2009, 2008a, although explicit models that exist now for grain size do not presently cover all of the ranges of conditions that one might encounter. Using a look-up table is a tacit acknowledgement that our modeling efforts are not comprehensive yet, and the table therefore takes the place of an explicit model in order to be able to address a broader range of conditions that might be encountered.…”

“…In our previously published descriptions (Bachmann, Nichols et al, 2010f, 2009, 2008a, we have outlined explicit models for retrievals of various quantities related to bearing strength such as soil moisture, grain size, and composition. The look-up table approach described here and in (Bachmann, Nichols et al, 2010f, 2009, 2008a does not attempt to retrieve these intermediate physical variables or use any of the explicit models for these variables that we have derived.…”

“…The correlations that exist between spectral reflectance and the geotechnical properties measured at the same location are the basis of this translation, and as described above, the method used here is a LUT approach (Bachmann, Nichols et al, 2010f, 2009, 2008a. Some of the fundamental properties that determine bearing strength include, but are not limited to, moisture, grain size, and composition.…”

“…Our methodology which uses a look-up table (LUT) approach for retrieving an estimate of dynamic deflection modulus (Zorn, 2005), i.e. bearing strength in units of pressure, appears in (Bachmann, Nichols et al, 2010f, 2009, 2008a. The spectralgeotechnical libraries that support retrieval of these products were collected during these four remote sensing and cal/val campaigns.…”