BRDF Striping and Stray LiDAR Points in Remote Sensing Hyperspectral Data

An analysis was conducted of a series of Hyperspectral UAV surveys over crops in Europe. The original researchers identified dark and light stripes in the orthorectified Hyperspectral data. The analysis concluded that the striping was due to variations in the Bidirectional Reflectance Distribution Function (BRDF) of the plants in the fields being studied. In this particular case, the effect was identified with Dynamic BRDF, where the leaves point toward the location of the sun. The variations were correlated with flight direction, UAV orientation and Solar Angle.

A second common artifact in Hyperspectral Remote Sensing data is also described, and again correlated with Solar Angle. In LiDAR data collected at the same time as the Hyperspectral data, clouds of points in the sky above the UAV are sometime observed. Analysis of some point clouds taken in full sunlight was conducted, and a strong correlation was found between the arrangements of the extraneous points in the sky and the Solar Angle. It was concluded that the extraneous points are the result of the photodetectors in the LiDAR getting a false return when pointed directly toward the sun.