Publications

Modeling Tri-Directional Reflectance Distribution Funtions (TRDF) with application to subpixel target detection

Zollweg, Joshua D.; Nandy, Prabal

Spatially unresolved targets, such as vehicles, reflect a radiance spectrum that is more complicated than the simple linear mixing of target and background material spectra. Although different materials in the target and background classes have Bi-Directional Reflectance Function (BRDF) dependent spectra, the unique geometry and orientation of a target object, in addition to the solar illumination and observation angles, define a more complex Tri-Directional Reflectance Function (TRDF) in which glints and shadows are important spectral contributors. For different observation scenarios, the apparent spectra of an unresolved target may vary significantly. However, since solar and observation angles are often known to operators of remote sensing instruments, well characterized TRDFs for specific targets allow for refinement in the estimation of the expected spectra of different unresolved targets. More accurately defined target classes may lead to improved performance in established subpixel target detection algorithms for remote sensing.