Remote sensing: the use of polarized visible light (PVL) to estimate surface soil moisture

Sunlight is unpolarized; if it is reflected from a soil surface it will become partially polarized. The degree of polarization will be dependent upon the soil surface roughness and moisture content. The study of polarized visible light (PVL) reflectance has developed in the past two decades, from the use of a non-imaging photometer-polarimeter to record the surface roughness of laboratory samples, to the use of a camera and polarizing filter to estimate surface soil moisture in the field. It is demonstrated that PVL recorded at a high phase angle, from up to light aircraft altitudes, can successfully estimate surface soil moisture. This is possible regardless of solar angle, soil albedo or soil slope, over a wide but not umlimited range of surface soil moisture states, but only if surface disturbance and cloud cover are minimized.While PVL cannot, in general, rival currently available techniques for the remote sensing of surface soil moisture it is eminently suitable where an estimate of surface soil moisture is required at low cost for a small area.