New global forest/non-forest maps from ALOS PALSAR data (2007–2010)
New global forest/non-forest maps from ALOS PALSAR data (2007–2010)
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DOI：
10.1016/j.rse.2014.04.014
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发表时间：
2014-04
影响因子：
13.5
通讯作者：
M. Shimada;T. Itoh;T. Motooka;Manabu Watanabe;T. Shiraishi;R. Thapa;R. Lucas
中科院分区：
文献类型：
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作者：
M. Shimada;T. Itoh;T. Motooka;Manabu Watanabe;T. Shiraishi;R. Thapa;R. Lucas
利用2007年至2010年每年获取的数据，以25微米的空间分辨率生成了4幅L波段合成孔径雷达相控阵HH和HV极化数据。森林的L波段HH和HV伽马零点(γ0)在不同地区之间存在差异，这归因于森林结构和植被/地表湿度条件的差异。因此，每个年度马赛克都采用了特定区域的后向散射阈值，生成了森林和非森林覆盖的全球地图，并由此生成了森林损失和森林收益的地图。使用度汇流项目、森林资源评估和谷歌地球图像进行的森林/非森林评估的总体符合率分别为85%、91%和95%。以2007年为基线，在同一地区的HH和HVγ0分别下降了0.040和0.028分贝(以0.006分贝99%的置信度)，这表明在四年期间，L波段雷达观测到的森林面积减少和/或全球地表平整度增加。这些地图为记录森林范围的变化提供了新的全球资源，并通过与历史(1992-1998年)日本地球资源卫星(JERS-1)SAR和即将(2014年)ALOS-2 PALSAR-2数据进行比较，为量化历史和未来动态提供了机会。本文生成和分析的四年PALSAR马赛克和森林/非森林数据向公众开放供免费下载，尽管分辨率较低(WWW1)。计划未来分发来自PALSAR和ALOS-2/PALSAR-2的较高(原始)分辨率数据集。
Four global mosaics of Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (SAR) HH and HV polarization data were generated at 25 m spatial resolution using data acquired annually from 2007 to 2010. Variability in L-band HH and HV gamma-naught (γ0) for forests was observed between regions, with this attributed to differences in forest structure and vegetation/surface moisture conditions. Region-specific backscatter thresholds were therefore applied to produce from each annual mosaic, a global map of forest and non-forest cover from which maps of forest losses and gain were generated. The overall agreement with forest/non-forest assessments using the Degree Confluence Project, the Forest Resource Assessment and Google Earth images was 85%, 91% and 95% respectively. Using 2007 as a baseline, decreases of 0.040 and 0.028 dB (with a 0.006 dB 99% confidence level) were observed in the HH and HV γ0respectively over the same areas suggesting a decrease in forest area and/or increased smoothing of the global surface at the L-band radar observation over the four-year period. The maps provide a new global resource for documenting the changing extent of forests and offer opportunities for quantifying historical and future dynamics through comparison with historical (1992–1998) Japanese Earth Resources Satellite (JERS-1) SAR and the forthcoming (from 2014) ALOS-2 PALSAR-2 data. Four year PALSAR mosaics and the forest/non-forest data, which were generated and analyzed in this paper, are opened to the public for free downloading albeit with coarser resolutions (WWW1). Future distribution of the higher (original) resolution datasets from PALSAR as well as the ALOS-2/PALSAR-2 is planned.