Polarization ratio approach to retrieve the bare surface roughness at x-band

Abstract

An observation has been carried out at different incidence angle by X-band scatterometer to retrieve the surface roughness when moisture was kept constant. Polarization ratio approach has been proposed to retrieve the surface roughness at constant moisture. A co-polarized (Horizontal-Horizontal; HH and Vertical-Vertical; VV) ratio (p=σ0HH/ σ0VV) ratio based model is proposed to retrieve the bare surface roughness. The regression analyses have been carried out to pre-decide the suitable incidence angle to observe the surface roughness (0.5 to 4.18 cm) at X-band. It was found that the suitable incidence angle to observe surface roughness (0.5 to 4.18 cm) at X-band with co-polarization ratio is 35° and least square optimization (LSE) method has been applied to retrieve the surface roughness when moisture is kept constant. The retrieved values of rms heights are in good agreement (root mean square error, RMSE-1.22) with observed values of rms heights. The significance of the results has been tested by F-ratio test and it was found quite significant. This type of results are helpful to use the microwave techniques to assess the surface roughness by the air-borne or space borne sensor and propose the suitable angle of incidence to observe the surface roughness at X-band. © 2007 by the IETE.