Lionel Loubersac

Spatial resolution improvement by merging MERIS-ETM images for coastal water monitoring

The Medium Resolution Imaging Spectrometer (MERIS) launched in March 2002 and has been providing images since June 2002. Before its launch, we had implemented a method to improve its resolution by merging its images with Landsat Enhanced Thematic Mapper images in order to preserve the best characteristics of the two images (spatial, spectral, temporal). We now present the results of this method for real MERIS images (level 1b and 2) in a coastal area. The robustness of the method is studied as well as the influence of the delay between the acquisitions of the two images.

Partial characterization of an exopolysaccharide secreted by a marine bacterium, Vibrio neocaledonicus sp. nov., from New Caledonia

Exopolysaccharides (EPS) are industrially valuable molecules with numerous useful properties. This study describes the techniques used for the identification of a novel Vibrio bacterium and preliminary characterization of its EPS.

Bathymetric Estimation Using MERIS Images in Coastal Sea Waters

Bathymetric estimation using remote sensing images has previously been applied to high spatial resolution imagery such as CASI, Ikonos, or SPOT but not on medium spatial resolution images (i.e., MERIS). This choice can be justified when there is a need to map the bathymetry on large areas. In this letter, we present the results of the bathymetry estimation over a large known area, the Gulf of Lion (France), expanding over 270times180 km

Satellite survey of seasonal trophic status and occasional anoxic 'malaigue' crises in the Thau lagoon using MERIS images

The Thau lagoon, located in southern France, suffers episodically from anoxic crises locally known as ‘malaïgue’. Such crises mostly occur under warm conditions, low winds leading to a strong eutrophication of the lagoon. The development of a sulphur bacterium sometimes gives locally to the waters a ‘milky turquoise’ appearance and leads to shellfish mortality. One of the indicators of the eutrophication status of the lagoon can be surveyed by the chlorophyll product provided by remote sensing images such as Medium Resolution Imaging Spectrometer (MERIS). In this paper we compare chl2 (or algal2) estimations provided by MERIS level 2 products and the ground measurements of chlorophyll a concentrations in water and we propose a linear correction of the chl2 MERIS product. The corrected chl2 estimations obtained over four years are analysed to understand the seasonal evolution of the trophic status of the Thau lagoon. We also study the influence of the anoxic crises of summers 2003 and 2006 on the chl2 estimations and we find a strong correlation between chl2 and the oxygen percentage at 1 m depth (0.70 for measurements in summers 2003 and 2006).

Fusion of MeRIS and ETM images for coastal water monitoring

Ocean colour monitoring is usually based on optical remote sensing with spatial resolutions around 1 km. This spatial scale is available with such sensors as NOAA-AVHRR,POLDER or SeaWiFS, which cover one to several thousand kilometers in a single swath and providing very short revisit periods. The MeRIS sensor, launched on board ENVISAT in 2002, was designed for sea colour observation, with a 300 meter spatial resolution, 15 programmable spectral bands and a 3 day revisit period. Tree hundred meter is a high resolution for an oceanographic sensors, but it is still too rough for coastal water monitoring, where physical and biological phenomena require better spatial resolution [1]. On the opposite, multispectral Landsat ETM images offer a suitable spatial resolution, but have only 4 spectral bands in the visible and near infrared spectrum, allowing poor spectral characterization. A few years ago, in order to combine the spectral resolution of MeRIS and the spatial resolution of Landsat ETM,we had implemented a merging method proposed by Zhukov et al. [2]. Before the launch of ENVISAT, we applied this method to simulated MeRIS images [3]. MeRIS was launched in March 2002 and has been providing images since June 2002. This method is now applied to real MeRIS images. Two product levels are considered. Level 1b contains radiance measurements at the top of the atmosphere for the calibrated and geocoded fifteen (15) MeRIS bands. Level 2 contains normalized surface reflectance and several geophysical and biophysical parameters such as algal pigment index, suspended sediment,Rayleigh-corrected vegetation indices, aerosol type, cloud albedo. The method was tested for radiance (level lb) and reflectance (level 2) over a coastal area of approximately 30times30 km2 located around the Thau lagoon (southern France).

Distribution and Characterization of Tar Ball Pollution on Beaches in Brittany (France) and Indonesia

Abstract Stranded tar along the Brittany coast and four test sites in Indonesia (Jakarta Bay, Malacca and Makassar Straits, Central South Java) were surveyed in 1982 in order to quantify and identify the possible origin of oil pollutants. The estimation of tar pollution was determined by a statistical methodology based on a stratified random sampling. Western Brittany and Jakarta Bay must be regarded among the areas most vulnerable to chronic oil pollution with respectively gross weight values of 76.9 ±115.6g/m and 812.7±219g/m, comparable to those of other coasts along major tanker routes such as Kuwait or Bermuda. The levels on the other sampled sites were relatively low in spite of such dense maritime traffic as in Malacca straits (15.4 ±5.4 g/m) or near the mouth of La Loire (12.2±15.9 g/m and less than 0.5 g/m in the Bay of Saint-Brieuc). Hydrocarbons in tar samples were examined by liquid and gas chromatography for a classification in crude oil residues, sludge residues and fuel oil. A multimethod a...

A Metadata Service for Managing Spatial Resources of Coastal Areas

Within the framework of the SYSCOLAG pluridisciplinary research programme on ICZM in the Languedoc-Roussillon region of France, we propose an ISO-19115-compliant metadata service to share informational resources. Each resource is described using a metadata form. Each form consists of textually and spatially controlled terms which are stored in a single DBMS (Postgres and Postgis). The graphical user-interfaces contain the expert knowledge (thematic and spatial ontologies) and include a mapping service (SVG and OGC-compliant WMS-WFS) that allows spatial and thematic queries to be addressed to the metadata service.

MeRis and ETM image fusion for spatial resolution improvement

MeRIS was launched in March 2002 and has been providing images since June 2002. Before its launch, we had implemented a method to improve its resolution by merging its images with Landsat ETM images in order to preserve the best characteristics of the two images (spatial, spectral, temporal). We now present the results of this method for real MeRIS images (level 1b and 2) in a coastal area. The robustness of the method is studied as well as the influence of the delay between the acquisitions of the two images.