SAR analysis of wetland ecosystems: Effects of band frequency, polarization mode and acquisition dates

Rapinel Sébastien, Betbeder Julie, Denize Julien, Fabre Elodie, Pottier Eric, Hubert-Moy Laurence. 2020. SAR analysis of wetland ecosystems: Effects of band frequency, polarization mode and acquisition dates. ISPRS Journal of Photogrammetry and Remote Sensing, 170 : 103-113.

Quartile : Outlier, Sujet : GEOGRAPHY, PHYSICAL / Quartile : Outlier, Sujet : GEOSCIENCES, MULTIDISCIPLINARY / Quartile : Q1, Sujet : IMAGING SCIENCE & PHOTOGRAPHIC TECHNOLOGY / Quartile : Q1, Sujet : REMOTE SENSING

Résumé : The availability of high spatial resolution synthetic aperture radar (SAR) sensors with a wide range of acquisition modes has increased greatly over the past decade and contributed significantly to the study of wetland ecosystems. However, the relative influence of acquisition configurations (i.e. band frequency, polarization mode, number of acquisition dates) in wetland analysis remains poorly explored. This article investigated the relative influence of X-/C-band frequency, dual-/quad-polarization and single-/multi-acquisition features on discrimination of vegetation types in 632 ha Ramsar-protected temperate riverine marshes (Mont-Saint-Michel Bay, France). Three SAR datasets (i.e. quad-pol/C-band, dual-pol/C-band and dual-pol/X-band) were generated from five pairs of TerraSAR-X and RADARSAT-2 images. First, a set of 25 SAR features, including backscattering coefficients and polarimetric parameters, was extracted from the SAR datasets. Second, correlation between each pair of images was calculated using the polarimetric parameter Shannon entropy to select the most similar pairs in the time series. Third, the importance of each SAR feature and modeling accuracy were calculated using a conditional random forest model for each of the three datasets. Finally, analysis of variance was performed to assess the impact of band frequency, polarization mode and number of acquisition dates on the classification of vegetation types. The results highlighted that although the time-shift of each pair of TerraSAR-X and RADARSAT-2 images was short (3–11 days), only three pairs were sufficiently similar, highlighting the high variability in wetland ecosystems. The polarimetric parameter Shannon entropy was the most discriminating feature, regardless of the frequency or polarization. Most variance in the model accuracy was explained by the number of acquisition dates (68%), followed by the frequency (23%), while polarization explained little. This article will help select the most suitable SAR sensor acquisition modes for wetland conservation.

Mots-clés Agrovoc : Radar à synthèse d'ouverture, écosystème forestier, conservation des terres, terre humide, polarisation, préservation de l'écosystème, conservation des forêts

Mots-clés libres : RADARSAT-2, TerraSAR-X, Conservation, Random forest

Classification Agris : U30 - Méthodes de recherche
P01 - Conservation de la nature et ressources foncières

Champ stratégique Cirad : CTS 1 (2019-) - Biodiversité

Auteurs et affiliations

• Rapinel Sébastien, Université de Rennes 2 (FRA) - auteur correspondant
• Betbeder Julie, CIRAD-ES-UPR Forêts et sociétés (CRI)
• Denize Julien, Université de Rennes 2 (FRA)
• Fabre Elodie, Université de Rennes (FRA)
• Pottier Eric, Université de Rennes I (FRA)
• Hubert-Moy Laurence, Université de Rennes 2 (FRA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/597061/)

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