Jean-Paul Deroin

Combining ALOS and ERS-2 SAR data for the characterization of tidal flats. Case study from the Baie des Veys, Normandy, France

Abstract To better understand the SAR backscattering of tidal flats’ sediments, a study was conducted in the framework of the ALOS Data European Node. The approach is mainly based on the analysis of a time series of ALOS data acquired from April to June 2008. The emphasis is on the spatial statistics of the underlying random surface of the tidal flat. Three ALOS cycles with interesting adjacent swath configurations were considered. The study comprised field work to establish the ground truth, and then the analysis of radar data. For this purpose combined PALSAR L-band HH and ERS-2 C-band VV data were explored, because dual-frequency data acquisition is needed for geophysical parameters retrieval. Co-polarized data are more relevant for the study of the tidal flat itself, whereas the HV polarization is suitable for identifying the presence of halophytic plants growing in the upper part of the tidal flat. Quad-polarization L-band data could be of great interest, but experiments could not be set up due to lack of suitable acquisitions. The C-band is more accurate for sensing the roughness of the finer sediments, whereas the L-band is more relevant for drawing the instantaneous limit of the sea. This paper briefly discusses the role of the local mean time for the study of areas experiencing high tidal range. For the test site located in Normandy, the ALOS acquisition time does not allow more than 55 per cent of the tidal flat to be exposed.

Implementing GIS regression trees for generating the spatial distribution of copper in Mediterranean environments: the case study of Lebanon

Soil contamination by heavy metals has become a widespread dangerous problem in many parts of the world, including the Mediterranean environments. This is closely related to the increase irrigation by waste waters, to the uncontrolled application of sewage sludge, industrial effluents, pesticides and fertilizers, to the rapid urbanization, to the atmospheric deposition of dust and aerosols, to the vehicular emissions and to many other negative human activities. In this context, this paper predicts the spatial distribution and concentration level of copper (Cu) in the 195 km2 of Nahr el-Jawz watershed coastal area situated in northern Lebanon using a geographic information system (GIS) and regression-tree analysis. The chosen area represents a typical case study of Mediterranean coastal landscape with deteriorating environment. Fifteen environmental parameters (parent material, soil type, pH, hydraulical conductivity, organic matter, stoniness ratio, soil depth, slope gradient, slope aspect, slope curvature, land cover/use, distance to drainage line, proximity to roads, nearness to cities, and surroundings to waste areas) were generated from satellite imageries, Digital Elevation Models (DEMs), ancillary data and/or field observations to statistically explain Cu laboratory measurements. A large number of tree-based regression models (214) were developed using (1) all parameters, (2) all soil parameters only, and (3) selected pairs of parameters. The best regression tree model (with the lowest number of terminal nodes) combined soil pH and surroundings to waste areas, and explained 77% of the variability in Cu laboratory measurements. The overall accuracy of the predictive quantitative copper map produced using this model (at 1 : 50,000 cartographic scale) was estimated to be ca. 80%. Applying the proposed tree model is relatively simple, and may be used in other coastal areas. It is certainly of significant interest to local governments and municipalities. It will serve several development projects concerned with improving the environmental conditions and the quality of living in coastal areas.

Remote Sensing Study of the Ancient Jabali Silver Mines (Yemen): From Past to Present

Archaeological research into the ancient Jabali silver mines in northern Yemen is a multidisciplinary project linking archaeologists, historians, and geologists, supported by remote satellite-based sensing. Mining companies are considering the development of the Jabali deposit for zinc ore. Some of the facilities, including a large open pit, will have a destructive impact on the old pits. Multispectral (Landsat TM, Terra ASTER, ALOS-AVNIR-2, etc.) and very high spatial resolution images such as QuickBird have been widely used for the geological setting and detail mapping of the different archaeological sites. The remote sensing data also provides a solid basis when it comes to detecting current operational sites.

Geological mapping in the zone of Chotts, Tunisia, using ALOS sensors

The three sensors onboard the Advanced Land Observing Satellite (ALOS) are the Phased Array L-band Synthetic Aperture Radar (PALSAR), the Panchromatic Remote-Sensing Instrument for Stereo Mapping (PRISM), and the Advanced Visible and Near-Infrared Radiometer type 2 (AVNIR-2). Each of them has been evaluated for the geological mapping of the Zone of Chotts, Tunisia. Both the endoreic basins and the surrounding ranges have been studied. The 10 m-resolution AVNIR-2 sensor is a good trade-off for geological mapping. The 2.5 m-resolution PRISM sensor with its stereoscopic capability is very useful for the detailed study of sedimentary layers. Copolarized radar data are relevant for the study of the flat itself but the C-band is more accurate for sensing the roughness of the finer sediments (sand veneers, evaporites, etc.). The HV polarization is suitable for identifying the presence of halophytic plants that fringe the upper part of the flat.

An Overview on 40 Years of Remote Sensing Geology Based on Arab Examples

Remote sensing techniques are particularly suitable for geological studies in arid regions such as the Arab world. Here, we present an overview of the main applications of satellite sensors to geology for geological mapping, tectonic and structural geology, hydrogeology, mining geology, geoarchaeology, oil and gas prospection, earthquake and seismicity, landslides and coastal erosion. The main characteristics of the sensors are discussed. In addition, three examples of modern remote sensing imagery show geology in Arab countries: The Dead Sea Fault in the Middle East as seen with the large-scale ALOS PALSAR (ScanSAR mode) image, the Bou Azzer Anticline (Morocco) viewed by multispectral Landsat TM and the evolution of the coastal front in Nouakchott (Mauritania), monitored with multi-temporal Landsat data.

Estimation of Surface Parameters of Tidal Flats Using Sentinel-1A SAR Data in the Northern Coast of Vietnam

Tidal flat is a special environment which is submerged during flood tide and exposing the air during ebb tide. Tidal flats in the north coast in Vietnam surfer diurnal tide with tide range varying from 0.3 m to 3.5 m. Along 350 km coastline of the study area, the diversity of constituent conditions forms various tidal flats with different characteristics. Soil moisture and surface roughness are the key parameters for the studies concerning tidal flat environment. These surface parameters of tidal flats can be investigated using inversion models with SAR data. This study applies the inversion method of the Oh model 2004 to estimate vertical surface roughness and soil moisture. Two Sentinel-1A SAR data are acquired and preprocessed to yield backscattering coefficients of VV and VH polarizations of C band. In condition of missing co-polarization data (HH) for fully applying the Oh inversion model, a calibration function is generated to calibrate estimated roughness and soil moisture. This is the first time that the surface roughness and soil moisture of tidal flats are successfully estimated from SAR data in the study area. Even now, the applications of the Oh model for estimating surface parameters of tidal flat using Sentinel-1A SAR images have not found yet in literatures. Vertical roughness after calibrating is estimated with an accuracy of 0.09 cm. The accuracy of estimated soil moisture of tidal flats is not assessed due to lacking the referent data. However, the estimated soil moisture is good correlation with the real environmental conditions in the study area.

Development of assisted road navigation by the drainage network

The objective of the research is to analyze the relationship between drainage and assisted navigation on the road. More specifically, to show how the drainage contributes to assisted road navigation. First, we extract the drainage of SRTM picture. In a second step, we integrated drainage and roads in a geographic information system (GIS). Finally, we processed in GIS, drainage and road network in order to highlight the characteristics of risk areas, construction sites of bridges, dams and computer aided navigation. The study shows that the drainage network and the road network integrated into a GIS leads to the production of an application that allows users and road managers to learn about the state of the road and help decision. The resulting application is an effective information on the state of the tool to help drive on-road driving and road network management.

Using remote sensing free software in scientific research

The aim of this paper is to present the remote sensing, the free open source software and their consequences on scientific research and education. This paper deals with some points which seem particularly interesting. The first part will define the concept of education, scientific research in the context of free open source software. The free open source software is expressed in the license (GNU project) on which its use must comply. A second part will describe the role of free open source software in education and scientific research. The third part will presents the remote detection and free open source software and the work we do with the two main software we use in the research.