A database of hydrology targets for the new DEM onboard Jason3

Denis Blumstein (CNES/LEGOS, France)

CoAuthors

Sylvain BIANCAMARIA (LEGOS, France); Jean-François CRETAUX (CNES/LEGOS, FRANCE); Stéphane CALMANT (LEGOS, FRANCE); Fabien BLAREL (LEGOS, FRANCE); Elena ZAKHAROVA (LEGOS, FRANCE); Sophie Le Gac (CNES, FRANCE); François BOY (CNES, FRANCE); Nicolas PICOT (CNES, FRANCE)

Event: 2017 Ocean Surface Topography Science Team Meeting

Session: Science IV: 25 years of satellite altimetry for Cryosphere and Hydrology: from experimental to emerging operational applications

Presentation type: Type Poster

On Jason-3, data acquisition over inland water bodies is performed in either Diode/DEM mode or Autonomous Mode [1]. The Diode/DEM tracking mode can be very useful in order to have the altimeter providing valid measurements over the water body even in difficult environments like rivers lying in the bottom of narrow valleys (see [2] for example). However, this tracking mode requires that the height of the targets of interest is known with a rather good exactitude (typically a dozen of meters). Otherwise, the remedy would be worse than the evil and the river would be missed by the altimeter for all the overpasses. It is then not a completely trivial task to build a global onboard DEM that meets this constraint.

Therefore, given the interest for the whole users community, LEGOS and CNES teams joined technical and scientific expertise to establish the right strategy for making such onboard DEMs. We first defined a small scale project over France (around 100 targets) where precise topography, water masks and in-situ measurements of water heights are publicly available. This allowed us to validate the methods during the commissioning of Jason3 taking benefit of the tandem phase with Jason2. The results of this validation are presented in [3]. In a second step, we recently expanded the database on a global scale with more than 4500 targets worldwide to build the new Jason3 onboard DEM. In the process, we paid a particular attention not to disturb acquisitions over hydrology targets already monitored in the databases providing measurement from spatial altimetry (GREALM, HYDROWEB and DAHITI). The implementation of the DEM in Jason-3 is presented in [4].

The poster will present the new global database, the expected improvements for spatial hydrology, the methods we have used to build it and some difficulties we had to overcome. We will also present the first results of validation if the new DEM has been put in operation soon enough before the meeting.

[1] Desjonqueres et al., Jason-3/POS-3B First results, OSTST 2016.
[2] Biancamaria et al., Satellite radar altimetry water elevations performance over a 200 m
wide river: Evaluation over the Garonne River, Advances in Space Research, Volume 59, Issue 1, 2017
[3] Biancamaria et al., Validation of Jason-3 tracking modes over French rivers, Rem. Sens. Env., submitted, 2017
[4] Le Gac et al., Update and validation of the onboard Jason-3 DEM for enhanced acquisitions over inland water targets, OSTST 2017
 

Poster show times:

RoomStart DateEnd Date
Concerto Ballroom Thu, Oct 26 2017,14:00 Thu, Oct 26 2017,18:00
Denis Blumstein
CNES/LEGOS
France
denis.blumstein@cnes.fr