Figure Twenty Figure 20.
Surface reflectance can vary depending on view angle.
This is primarly due to mutual shadowing which increases as the view position moves away from alignment with the sun's position. This figure shows the classic directional signature of a forested surface. The peak at -30 degrees is known as the hotspot, or the view angle at which the sensor and the sun are aligned. In this position, no shadows are viewed, and so the scene appears brightest. Depending on the characteristics of the surface, the shape of this curve will be different.