부산대학교 도서관

In this study, the dominant and medium scattering phases generated by the Touzi decomposition are investigated for discontinuous permafrost mapping in peatland regions. Polarimetric ALOS2, LIDAR and field data were collected in the middle of August 2014, at the maximum permafrost thaw conditions, over discontinuous permafrost distributed within wooded palsa bogs and peat plateaus near the Namur Lake (Northern Alberta). The ALOS2 image, which was miscellaneously calibrated with antenna cross-talk (-33dB), much higher than the actual ones, is recalibrated. This leads to a reduction of the residual calibration error (down to -43 dB), and permit a significant improvement of the dominant and medium scattering type phase (20°-to-30°) over peatlands underlain by discontinuous permafrost. The Touzi decomposition, Cloude-Pottier α-H incoherent target scattering decomposition, and the HH-VV phase difference are investigated, in addition to the conventional multi-polarization (HH, HV, and VV) channels, for discontinuous permafrost mapping using the recalibrated ALOS2 image. A LiDAR-based permafrost classification developed by Alberta Geological Survey (AGS) is used, in conjunction with the field data collected during the ALOS2 image acquisition, for the validation of the results. It is shown that the dominant and scattering type phases are the only polarimetric parameters which can detect peatland subsurface discontinuous permafrost. The medium scattering type phase, ϕ s2 , performs better than the dominant scattering type phase, ϕ s1 , and permits a better detection of subsurface discontinuous permafrost in peatland regions. ϕ s2 also allows for better discrimination of areas underlain by permafrost from the non-permafrost areas. The medium Huynen maximum polarisation return (m2) and the minimum degree of polarisation (DoP), pmin, can be used to remove the scattering type phase ambiguities that might occur in areas with deep permafrost (more than 50cm depth). The excellent performances of polarimetric PALSAR2 in term of NESZ (-37 dB) permit the demonstration of the very promising L-band long penetration SAR capabilities for enhanced detection and mapping of relatively deep (up to 50 cm) discontinuous permafrost in peatlands regions [1].