Mapping Forest Cover and Forest Cover Change with Airborne S-Band Radar
Mapping Forest Cover and Forest Cover Change with Airborne S-Band Radar
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DOI：
10.3390/rs8070577
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发表时间：
2016-07
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通讯作者：
Ramesh K. Ningthoujam;K. Tansey;H. Balzter;K. Morrison;S. Johnson;F. Gerard;C. George;G. Burbidge;S. Doody;N. Veck;G. Llewellyn;T. Blythe
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作者：
Ramesh K. Ningthoujam;K. Tansey;H. Balzter;K. Morrison;S. Johnson;F. Gerard;C. George;G. Burbidge;S. Doody;N. Veck;G. Llewellyn;T. Blythe
对森林覆盖、森林碳储量以及森林砍伐和退化造成的碳排放的评估日益成为可持续资源管理、应对生物多样性丧失和减缓气候变化政策的重要组成部分。卫星遥感提供了定期绘制全球森林覆盖图的唯一手段。然而，利用光学数据进行森林分类因其对三维冠层结构不敏感以及遮蔽许多森林区域的云层而受到限制。合成孔径雷达 (SAR) 传感器越来越多地用于缓解这些问题，主要是在电磁频谱的 L、C 和 X 波段领域。 S 波段尚未为此目的进行系统研究。考虑到英国建造的 NovaSAR-S 卫星任务，本研究评估了偏振 S 波段 SAR 对森林特征描述的好处。密歇根微波冠层散射 (MIMICS-I) 辐射传输模型用于了解 S 波段森林冠层的散射机制。与所有偏振和入射角的土壤特征相比，MIMICS-I 模型揭示了对森林冠层的强烈 S 波段反向散射敏感性。对英格兰南部萨文纳克森林温带混交林上空的机载 S 波段 SAR 图像的信息内容进行了分析。根据建模结果，S 波段 HH 和 VV 偏振雷达后向散射以及雷达森林退化指数 (RFDI) 用于森林/非森林最大似然分类，空间分辨率为 6 m（70% 总体精度，κ = 0.41）和 20 m（63% 总体精度，κ = 0.27）。结论是，S 波段 SAR（例如 NovaSAR-S）很可能适合监测森林覆盖及其变化。
Assessments of forest cover, forest carbon stocks and carbon emissions from deforestation and degradation are increasingly important components of sustainable resource management, for combating biodiversity loss and in climate mitigation policies. Satellite remote sensing provides the only means for mapping global forest cover regularly. However, forest classification with optical data is limited by its insensitivity to three-dimensional canopy structure and cloud cover obscuring many forest regions. Synthetic Aperture Radar (SAR) sensors are increasingly being used to mitigate these problems, mainly in the L-, C- and X-band domains of the electromagnetic spectrum. S-band has not been systematically studied for this purpose. In anticipation of the British built NovaSAR-S satellite mission, this study evaluates the benefits of polarimetric S-band SAR for forest characterisation. The Michigan Microwave Canopy Scattering (MIMICS-I) radiative transfer model is utilised to understand the scattering mechanisms in forest canopies at S-band. The MIMICS-I model reveals strong S-band backscatter sensitivity to the forest canopy in comparison to soil characteristics across all polarisations and incidence angles. Airborne S-band SAR imagery over the temperate mixed forest of Savernake Forest in southern England is analysed for its information content. Based on the modelling results, S-band HH- and VV-polarisation radar backscatter and the Radar Forest Degradation Index (RFDI) are used in a forest/non-forest Maximum Likelihood classification at a spatial resolution of 6 m (70% overall accuracy, κ = 0.41) and 20 m (63% overall accuracy, κ = 0.27). The conclusion is that S-band SAR such as from NovaSAR-S is likely to be suitable for monitoring forest cover and its changes.