H

-alpha decomposition is modified for dual-polarization SAR data applications. The boundary of the feasible region in H-a plane for dual-polarization cases is derived. It is different from full polarization that the boundary is symmetrical with respect to alpha being 45 derees. Performance of scattering mechanism identification is analyzed using the modified H-a decomposition for HH-VV

HH-HV

and HV-VV SARs

and a feasible division of HH-VV

H

-alpha plane is obtained. It is demonstrated theoretically that only HH-VV SAR can distinguish three basic scattering mechanisms from an isotropic surface

a dipole

and an isotropic dihedral. Experimental results using real data

acquired by the NASA/JPL AIR

SAR and DLR E-SAR

illustrate that eight scattering mechanisms inside the feasible region in

H

-a plane can be identified on the whole by HH-VV SAR

and only low entropy and high entropy scatterings can be divided by HH-HV and HV-VV SARs.