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Ocean Surface Topography from Space
Altimetric Waveforms In Coastal Regions and Continental Surfaces


Fernando Nino - (LEGOS)

  Denis Blumstein
Florence Birol
Stéphane Calmant
Fabien Blarel


Altimetric Waveforms In Coastal Regions and Continental Surfaces
Reconstructing a DEM of southern India using overlapping altimetry waveforms using ASTER v2 data and Jason-2 waveforms for pass 79.
During the last 20 years, altimetry missions have provided data that have been highly valuable for answering essential questions on ocean dynamics and the climate record. The growing body of altimetry data is even more valuable when multiple missions can readily be compared; providing a multi-mission homogeneous state of the art dataset has been one of the main goals of the CTOH (Centre de Topographie des Océans et de l'Hydrosphère) as a French observation service dedicated to satellite altimetry. However, data provided by CTOH has historically been limited to GDR products. Currently available storage facilities and computing power make possible the study of a more basic data form, the radar echo waveforms.

This proposal has two main objectives: (1) to extend the CTOH service from GDR products to waveform SGDR products and (2) maximize information retrieval over continental surfaces and coastal regions derived from the combined analysis of multiple altimeter waveforms.

Even though SGDRs are already provided by space agencies, these data are not easy to obtain and their format is, frequently, specific to each mission. In practical terms, any researcher willing to use this data needs to do much tinkering in order to adapt the data to his or her particular workflow. This proposal, in the framework of an ongoing initiative with colleagues of the Toulouse region, aims to provide researchers not only the infrastructure where normalized SGDRs can be found (i.e. provided in a standard format for all available missions), but also a toolbox and a canvas to quickly create any processing involving the SGDRs.

Pulse to pulse correlations in altimeter echoes are strong in continental surfaces and coastal areas, even when separated by long time intervals. Our second objective is to explore new processing approaches of these data (with the RESIPE project for waveform inversion) as well as providing support for researchers working directly with waveforms, particularly surface characterization based on waveforms in the cryosphere, and new applications based on waveform inversion to obtain the backscatter (σ0) distribution using Tournadre[2011]'s method. For the particular case of water bodies on continental surfaces, we will also systematically apply Bercher[2008]'s method for assessment of the quality of altimetry-derived time series of water-levels combined to the classical crossover-point validation methodology Legresy et al. [2007].

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