Assessment of L-Band SAR Data at Different Polarization Combinations for Crop and Other Landuse Classification
Ramesh S. Hooda
In the present study, evaluation of L-band SAR data at different polarization combinations in linear, circular as well as hybrid polarimetric imaging modes for crop and other landuse classifications has been carried out. Full-polarimetric radar data contains all the scattering information for any arbitrary polarization state, hence data of any combination of transmit and receive polarizations can be synthesized, mathematically from full-polarimetric data. Circular and various modes of hybrid polarimetric data, (where the transmitter polarization is either circular or orientated at 45°, called π/4 and the receivers are at horizontal and vertical polarizations with respect to the radar line of sight) were synthesized (simulated) from ALOS-PALSAR full-polarimetric data of 14th December 2008 over central state farm central latitude and longitude 29°15'N/75°43'E and bounds for northwest corner is 29°24'N/75°37'E and southeast corner is 29°07'N/75°48'E in Hisar, Haryana (India). Supervised classification was conducted for crops and few other landuse classes based on ground truth measurements using maximum-likelihood distance measures derived from the complex Wishart distribution of SAR data at various polarization combinations. It has been observed that linear full-polarimetric data showed maximum classification accuracy (92%) followed by circular-full (89%) and circular-dual polarimetric data (87%), which was followed by hybrid polarimetric data (73-75%) and then linear dual polarimetric data (63-71%). Among the linear dual polarimetric data, co-polarization complex data showed better classification accuracy than the cross-polarization data. Also multi-date single polarization SAR data over central state farm during rabi (winter) season was analyzed and it was observed that single date full-polarimetric SAR data produced equally good classification result as the multi-date single polarization SAR data.