Integration of radar and Landsat-derived foliage projected cover for woody regrowth mapping, Queensland, Australia

REMOTE SENSING OF ENVIRONMENT

卷:100

Article

Lucas, RM ; Cronin, N ; Moghaddam, M ; Lee, A ; Armston, J ; Bunting, P ; Witte, C

关键词: remote sensing;    synthetic aperture radar;    Landsat;    regrowth mappings;    land cover change;    biomass;    Queensland;    Australia;   

DOI  :  10.1016/j.rse.2005.09.020

来源: Elsevier

【 摘 要 】

In Queensland, Australia, forest areas are discriminated from non-forest by applying a threshold (similar to 12%) to Landsat-derived Foliage Projected Cover (FPC) layers (equating to similar to 20% canopy cover), which are produced routinely for the State. However, separation of woody regrowth following agricultural clearing cannot be undertaken with confidence, and is therefore not mapped routinely by State Agencies. Using fully polarimetric C-, L- and P-band NASA AIRSAR and Landsat FPC data for forests and agricultural land near Injune, central Queensland, we corroborate that woody regrowth dominated by Brigalow (Acacia harpophylla) cannot be discriminated using either FPC or indeed C-band data alone, because the rapid attainment of a canopy cover leads to similarities in both reflectance and backscatter with remnant forest. We also show that regrowth cannot be discriminated from non-forest areas using either L-band or P-band data alone. However, mapping can be achieved by thresholding and intersecting these layers, as regrowth is unique in supporting both a high FPC (> similar to 12%) and C-band SAR backscatter (>similar to -18 dB at HV polarisation) and low L-band and P-band SAR backscatter (e.g. <= similar to 14 dB at L-band HH polarisation). To provide a theoretical explanation, a wave scattering model based on that of Durden et al. [Durden, S.L., Van Zyl, J.J. & Zebker, H.A. (1989). Modelling and observation of radar polarization signature of forested areas. IEEE Trans. Geoscience and Remote Sensing, 27, 290-301.] was used to demonstrate that volume scattering from leaves and small branches in the upper canopy leads to increases in C-band backscattering, (particularly HV polatisations) from regrowth, which increases proportionally with FPC, By contrast, low L-band and P-band backscatter occurs because of the lack of double bounce interactions at co-polarisations (particularly HH) and volume scattering at HV polarisation from the stems and branches, respectively, when their dimensions are smaller than the wavelength. Regrowth maps generated by applying simple thresholds to both FPC and AIRSAR L-band data showed a very close correspondence with those mapped using same-date 2.5 m Hymap data and an average 73.7% overlap with those mapped through time-series comparison of Landsat-derived land cover classifications. Regrowth mapped using Landsat-derived FPC from 1995 and JER-1 SAR data from 1994 - 1995 also corresponded with areas identified within the time-series classification and true colour stereo photographs for the same period, The integration of Landsat FPC and L-band SAR data is therefore expected to facilitate regrowth mapping across Queensland and other regions of Australia, particularly as Japan's Advanced Land Observing System (ALOS) Phase Arrayed L-band SAR (PALSAR), to be launched in 2006, will observe at both L-band HH and HV polarisations. (C) 2005 Published by Elsevier Inc.

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