Impacts of Fully Illuminated Targets on Partially Shaded Backgrounds for a Multiclass Subpixel Target Detection Scenario

Objects on Earth with 3-dimensional geometries cast shadows onto the underlying background due to the obstruction of direct solar radiation. This phenomenon is considered for a multiclass subpixel target detection scenario, where the mixed pixels consist of materials from varying percentages of an illuminated target and partially shaded background. Hyperspectral data collected from UAS-based instruments and novel subpixel targets were used for the analyses. The novel targets enabled empirical observations of fully illuminated targets on partially shaded backgrounds. To assist in developing inferences on the impacts of detection, model reflectance spectra were generated for mixed pixels with fully illuminated and fully shaded background conditions. The modeling approach was validated with the empirical observations. The results imply the shadow effect is an important system parameter for subpixel target percentages of 20% or less, for the multiclass scenario and particular targets explored.