Mapping Mangrove Extent and Canopy Height in Gabon Using Interferometric Coherence and Freeman-Durden Decomposition from L-band ALOS/PALSAR-2
Abstract
Mangroves are woody plants found along tropical and subtropical coastlines. They provide substantial ecological and societal value: serving as a buffer for terrestrial life, offering a rich habitat for coastal plants and wildlife, and delivering significant carbon storage. As a result, monitoring the health of mangrove forests is of prime importance due to the changing climate and changing coastlines.
In our study spanning the entire Gabonese coast, we utilize L-band spaceborne ALOS/PALSAR-2 products to determine mangrove extent, classify different mangrove types, and estimate mangrove canopy heights in the coastal regions of Gabon. For this study, we use single look complex data (SLCs) acquired during the spring of 2015 and 2016 in order to derive both interferometric (InSAR) and polarimetric (PolSAR) data products. Using HH-polarized InSAR coherence with zero spatial baseline, we observe that the temporal decorrelation differentiates mangroves from other forests species and the ocean. In fact, we are able to estimate forest height due to its strong correlation with canopy height derived from TanDEM-X. From these important observations, we are able to classify dwarf and tall mangroves within the mangrove forest. Furthermore, we analyze the different polarimetric scattering mechanisms that arise within mangrove forests using the Freeman-Durden decomposition. Previously, such studies have predominantly focused on radar backscatter alone, but we show the added value of InSAR techniques for such ecological analysis. In summary, we demonstrate the value of using the combination of PolSAR and repeat-pass InSAR products to monitor mangrove forests at a large regional scale, showing that coherence is sensitive to mangrove height and that double bounce scattering is sensitive to various mangrove structures in these forests. We hope our SAR analysis can benefit future global mangrove studies. This study also demonstrates an important science application for the upcoming NISAR mission.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H43N2273L
- Keywords:
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- 1855 Remote sensing;
- HYDROLOGY