Conference Agenda
Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).
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📌Poster Session and Networking Aperitivo 🍷 Location: Lower Lobby | |
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Validation of DTM Derived from P-band SAR Under the Amazon Rainforest: from Airborne Surveys to the Biomass Perspective 1: UFPA, Brazil; 2: Lebanese University, Lebanon; 3: CESBIO, France; 4: UFRA, Brazil Validation of DTM Derived from P-band SAR Under the Amazon Rainforest: from Airborne Surveys to the Biomass Perspective Laurent Polidori, Universidade Federal do Pará (UFPA), Belém, Brazil Mhamad El Hage, Lebanese University (UL), Tripoli, Liban Laurent Ferro-Famil, ISAE-SUPAERO / CESBIO, Toulouse, France Ludovic Villard, CNRS / CESBIO, Toulouse, France Carlos Caldeira, Universidade Federal Rural da Amazônia (UFRA), Belém, Brazil Topics: BIOMASS calibration and validation, SAR Tomography (Tomo-SAR) Keywords: Biomass, tomography, DTM, Amazon Presentation preference : oral Digital elevation models through forests is one of the most important products of the Biomass mission, although the case of tropical dense forests remains challenging. Previous tests carried out on the experimental sites of the TropiSAR (Paracou, French Guiana) and AfriSAR (Gabon) preparation campaigns have demonstrated the feasibility of extracting elevation from the P-band radar tomographic signal, but cannot fully conclude on the potential of Biomass to produce a DTM, for several reasons: - The areas imaged are too small (we do not have access to the low frequencies of the terrain elevation or to a significant hydrographic catchment area enabling hydrographic coherence to be analysed). - Slope is not assessed, even though it is a more relevant variable than elevation for most DTM applications. - The quality indicators are incomplete, inspired by the practices of official mapping agencies which generally do not take into account the needs of the users of their products. Bias and standard deviation do not take into account the autocorrelation of the error and therefore do not allow conclusions to be drawn about the fidelity of the model to the landforms. A wider range of quality criteria must be considered, linked to the expectations of the users in the field of the geosciences. - The Lidar elevation product is considered to be a ‘perfect’ reference, which is highly questionable. In order to assess more comprehensively the potential of P-band radar for relief mapping under forest cover, we analysed InSAR products derived from aerial P-band radar acquisitions, available over an area of 160,000 km² in northern Brazil. Different quality criteria were considered, divided into two parts: - External validation consists in comparing the DTM with reference data to characterise elevation and slope errors, their statistical distribution, their spatial distribution and the influence of landscape and acquisition parameters. The reference data are mainly Lidar surveys, which are more accurate but have a more limited spatial coverage. - Internal validation consists in verifying the geomorphological realism and the coherence of the hydrographic network, based on hypotheses such as the fractal behaviour of terrestrial relief in geological environments shaped by water runoff and structured into watersheds. Based on this work, a strategy for validating the MNT derived from Biomass is being implemented in order to better understand the potential and limitations of this product once it becomes available in the Amazon region, for a variety of purposes in geoscience and water management. | |
