Techniques of ground-truth measurements of desert-scrub structure

Inversion of remote sensing data taken over a desert scrub surface in Texas with a multidirectionally viewing field radiometer, PARABOLA, yields the value of 0.12 for the protrusion parameter, s, (the projection on a vertical plane of plants per unit area) if isotropy (Lambert law) is assumed for the underlying soil. However, a significantly higher value of s, in the range 0.15 to 0.20, can be inferred if the soil is assumed anisotropic. It is concluded that in remote sensing of sparse vegetation, it is important to know the reflectance characteristics of the underlying soil. Other techniques that can be used to infer desert scrub vegetation structure include various photographic techniques, and measurements of reflected radiance from zenith for a range of solar elevation angles on a clear day.