THE EXTRACTION OF SOIL DIELECTRIC-PROPERTIES FROM AIRSAR DATA

Complex dielectric constants determined by inversion of the polarized returns of radar images acquired in wet conditions clearly delineate t he distribution of saline soils in the Tragowel Plains Irrigation Area of Victoria, Australia. There is good agreement between the areas del ineated as having anomalous dielectric constants by the radar backscat ter inversion techniques with saline areas as defined by geophysics an d as inferred from dielectric constants determined in the held. The ra dar-determined complex dielectric constants are significantly smaller than might be expected from the known moisture contents of the soils a t the time of image acquisition. The magnitudes of P-band radar-determ ined dielectric constants most closely approach those expected from he ld determinations although the distribution of L-band-determined diele ctric constants give the best discrimination between saline and non-sa line areas as seen at the surface. Modification of the inversion algor ithm to allow for the effects of vegetation produces complex dielectri c constant magnitudes in the saline regions that are closer to expecte d values but still underestimate the complex dielectric constant in no n-saline regions. The more general regional distribution of high diele ctric areas seen at P-band may be a more accurate indication of the sa linity at depth.