Mohamad El Hajj

French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · Centre de Recherche de Montpellier

The complex, dynamic and narrow boundaries between vegetation types make wetland mapping challenging. Hereafter the case study of the Hamoun-e-Hirmand wetland is considered by analysing eight Synthetic Aperture Radar (SAR) Images acquired in dry and wet periods with three wavelengths (X-band ~ 3 cm, C-band ~ 6 cm, and L-band ~ 25 cm), three polariz...

Monitoring crop status at plot scale in agricultural areas is essential for crop and irrigation management and yield optimization. The Vegetation Optical Depth (VOD) of canopy is directly related to the canopy water content, and thus, it represents an effective tool for crop health monitoring. Currently, VOD is provided at low spatial resolution wh...

The ability of Synthetic Aperture Radar (SAR) Sentinel-1 data to detect the main wheat phenological phases was investigated in the Bekaa plain of Lebanon. Accordingly, the temporal variation of Sentinel-1 (S1) signal was analyzed as a function of the phenological phases’ dates observed in situ (germination; heading and soft dough), and harvesting....

This paper presents a comparison between the Sentinel-1/Sentinel-2-derived soil moisture product at plot scale (S2MP) and the new Copernicus surface soil moisture (C-SSM) product at 1-km scale over a wide region in southern France. In this study, both products were first evaluated using in situ measurements obtained by the calibrated time delay ref...

Mapping irrigated plots is essential for better water resource management. Today, the free and open access Sentinel-1 (S1) and Sentinel-2 (S2) data with high revisit time offers a powerful tool for irrigation mapping at plot scale. Up to date, few studies have used S1 and S2 data to provide approaches for mapping irrigated plots. This study propose...

Soil moisture plays a key role in various processes at the soil-vegetation-atmosphere interface, such as evapotranspiration, infiltration and runoff. In this study, we firstly propose a global analysis of Sentinel-1 (S1) & Sentinel-2 (S2) data potential to retrieve soil moisture. Two approaches are tested. The first one is based on neural network a...

The main purpose of this study is to investigate the performance of two radar backscattering models; the calibrated integral equation model (CIEM) and the modified Dubois model (MDB) over an agricultural area in Karaj, Iran. In the first part, the performance of the models is evaluated based on the field measurement and the mentioned backscattering...

Wetland destruction is currently one of the greatest environmental problems in the world. Despite the functions of wetlands, thesevaluable ecosystems have steadily decreased becau se of human activ ities and climate chang e. To protect these valuable ecosystems,wetland restoration and rehabilitation are important operations that have been conducted...

This study proposes an effective method to map rice crops using the Sentinel-1 SAR (Synthetic Aperture Radar) time series over the Camargue region, Southern France. First, the temporal behavior of the SAR backscattering coefficient over 832 plots containing different crop types was analyzed. Through this analysis, the rice cultivation was identifie...

The aim of this paper is to map the aboveground biomass (AGB) in Gabon. First, a random forest (RF) model that relates reference AGB values to remote sensing (RS)-derived variables (mainly radar and optical images) was built, and the significant predictive variables were determined. Second, the built RF model was applied to the significant RS-deriv...

The objective of this paper is to present an analysis of Sentinel-1 derived surface soil moisture maps (S1-SSM) produced with high spatial resolution (at plot scale) and a revisit time of six days for the Occitanie region located in the South of France as a function of precipitation data, in order to investigate the potential of S1-SSM maps for det...

This paper assesses the potential of Synthetic Aperture Radar (SAR) in the C and L bands to penetrate into the canopy cover of wheat, maize and grasslands. For wheat and grasslands, the sensitivity of the C and L bands to in situ surface soil moisture (SSM) was first studied according to three levels of the Normalized Difference Vegetation Index (N...

This paper presents a technique for the mapping of soil moisture and irrigation, at the scale of agricultural fields, based on the synergistic interpretation of multi-temporal optical and Synthetic Aperture Radar (SAR) data (Sentinel-2 and Sentinel-1). The Kairouan plain, a semi-arid region in central Tunisia (North Africa), was selected as a test...

The objective of this paper is to evaluate the potential of Sentinel-1 Synthetic Aperture Radar “SAR” data (C-band) for monitoring agricultural frozen soils. First, investigations were conducted from simulated radar signal data using a SAR backscattering model combined with a dielectric mixing model. Then, Sentinel-1 images acquired at a study site...

Wetland mapping is the first step in wetland monitoring and conservation process. But the dynamic conditions and narrow boundaries of wetlands make it difficult to map. In this regards, Synthetic Aperture Radar (SAR) systems are useful, because these data can be used to map the surface water extent, saturated soils, flooded vegetation, and changes...

This study evaluates the accuracy of several recent remote sensing Surface Soil Moisture (SSM) products at sites in southwestern France. The products used are Soil Moisture Active Passive “SMAP” (level 3: 36 km × 36 km, level 3 enhanced: 9 km × 9 km, and Level 2 SMAP/Sentinel-1: 1 km × 1km), Advanced Scatterometer “ASCAT” (level 2 with three spatia...

In this chapter we propose the use of a drought index based on a temporal series of NDVI MODIS images for the monitoring of drought in France during the last fifteen years at a spatial resolution of 250 m. The goal is to show how to track and map drought using QGIS free software. The areas of agricultural, urban and forest areas will be provided fo...

This chapter focuses on the reliability of remote sensing imagery combined with topographic and bathymetric data to map the coastal wetland communities in Ichkeul marshes. It combines both the object-oriented classification of high spatial resolution imagery and the integrated topographic-bathymetric digital terrain model (topo-bathymetric DTM) in...

The purpose of this study is to analyze the potential of Sentinel-1 C-band SAR data in VV polarization for estimating the surface roughness (Hrms) over bare agricultural soils. An inversion technique based on Multi-Layer Perceptron neural networks is used. It involves two steps. First, a neural network (NN) is used for estimating the soil moisture...

L’objectif de ce chapitre et de montrer comment cartographier l’humidité de surface des sols dans des parcelles agricoles (cultures d’été/hiver) et sur des prairies en utilisant le logiciel libre QGIS, par couplage d’images radar (Radar à Synthèse d’Ouverture "RSO") et optique à haute résolution spatiale (~10 m x 10 m).

Dans ce chapitre, nous proposons l’utilisation d’un indice de sécheresse fondé sur une série temporelle d’images de NDVI MODIS pour le suivi de la sécheresse en France durant ces dix-sept dernières années, à une résolution spatiale de 250 m. L’objectif est de montrer comment suivre et cartographier la sécheresse en utilisant le logiciel libre QGIS....

Les milieux humides littoraux constituent une interface terre-mer sensible où se côtoient les facteurs d’origines marines et terrestres et où le poids de chacun peut conditionner l’évolution vers l’un ou l’autre milieu. Leurs écosystèmes résultent de l’interaction de nombreux facteurs environnementaux incluant les processus hydrologiques, géomorpho...

This chapter shows how to map the surface soil moisture over agricultural plots and grasslands using the free and open-source software quantum geographic information system (QGIS), by coupling radar (synthetic aperture radar (SAR)) and optical images acquired at high spatial resolution (~10 m x 10 m). The chapter describes the implementation of QGI...

This chapter focuses on the reliability of remote sensing imagery combined with topographic and bathymetric data to map the coastal wetland communities in Ichkeul marshes. It combines both the object‐oriented classification of high spatial resolution imagery and the integrated topographic‐bathymetric digital terrain model (topo‐bathymetric DTM) in...

Ce chapitre montre comment cartographier l'humidité superficielle du sol sur les parcelles agricoles et les prairies à l'aide du système d'information géographique quantique (SIGQ) logiciel libre et open-source, en couplant des images radar (radar à synthèse d'ouverture (SAR)) et des images optiques acquises à haute résolution spatiale (~10 m x 10...

This chapter shows how to map the surface soil moisture over agricultural plots and grasslands using the free and open-source software quantum geographic information system (QGIS), by coupling radar (synthetic aperture radar (SAR)) and optical images acquired at high spatial resolution (~10 m x 10 m). The chapter describes the implementation of QGI...

In this chapter we propose the use of a drought index based on a temporal series of NDVI MODIS images for the monitoring of drought in France during the last fifteen years at a spatial resolution of 250 m. The goal is to show how to track and map drought using QGIS free software. The areas of agricultural, urban and forest areas will be provided fo...

This chapter focuses on the reliability of remote sensing imagery combined with topographic and bathymetric data to map the coastal wetland communities in Ichkeul marshes. It combines both the object‐oriented classification of high spatial resolution imagery and the integrated topographic‐bathymetric digital terrain model (topo‐bathymetric DTM) in...

Soil moisture mapping at a high spatial resolution is very important for several applications in hydrology, agriculture and risk assessment. With the arrival of the free Sentinel data at high spatial and temporal resolutions, the development of soil moisture products that can better meet the needs of users is now possible. In this context, the main...

The main objective of this study is to analyze the potential use of Sentinel-1 (S1) radar data for the estimation of soil characteristics (roughness and water content) and cereal vegetation parameters (leaf area index (LAI), and vegetation height (H)) in agricultural areas. Simultaneously to several radar acquisitions made between 2015 and 2017, us...

The objective of this paper is to propose a new semi-empirical radar backscattering model for bare soil surfaces based on the Dubois model. A wide dataset of backscattering coefficients extracted from SAR (synthetic aperture radar) images and in situ soil surface parameter measurements (moisture content and roughness) is used. This dataset contains...

This study aimed to assess the potential of GLAS (Geoscience Laser Altimeter System) LiDAR data to overcome the saturation at high AGB values of existing AGB map on Madagascar (Vieilledent's AGB map [1]). First, spatially distributed estimations of AGB were obtained from GLAS data. Second, the difference between the Vieilledent's AGB map and GLAS d...

This study aimed to assess the potential of GLAS (Geoscience Laser Altimeter System) LiDAR data to overcome the saturation at high AGB values of existing AGB map on Madagascar (Vieilledent's AGB map [1]). First, spatially distributed estimations of AGB were obtained from GLAS data. Second, the difference between the Vieilledent's AGB map and GLAS d...

The main goal of this paper is to assess the radiometric stability of the new Sentinel-1A (S-1A) SAR (Synthetic Aperture Radar) sensors. The S-1A radiometric stability was assessed by analyzing the temporal variations of the backscattering coefficient (σ°) returned from invariant targets. The results show three stable sub-time series of S-1A data....

Mapping forest AGB (Above Ground Biomass) is of crucial importance to estimate the carbon emissions associated with tropical deforestation. This study proposes a method to overcome the saturation at high AGB values of existing AGB map (Vieilledent's AGB map) by using a map of correction factors generated from GLAS (Geoscience Laser Altimeter System...

The aim of this paper is to evaluate the most used radar backscattering models (Integral Equation Model "IEM", Oh, Dubois, and Advanced Integral Equation Model "AIEM") using a wide dataset of SAR (Synthetic Aperture Radar) data and experimental soil measurements. These forward models reproduce the radar backscattering coefficients (σ⁰) from soil su...

The aim of this paper is to evaluate the most used radar backscattering models (Integral Equation Model "IEM", Oh, Dubois, and Advanced Integral Equation Model "AIEM") using a wide dataset of SAR (Synthetic Aperture Radar) data and experimental soil measurements. These forward models reproduce the radar backscattering coefficients ) from soil su...

The objective of this paper is to propose a new semi-empirical radar backscattering model for bare soil surfaces based on the Dubois model. A wide dataset of backscattering coefficients extracted from synthetic aperture radar (SAR) images and in situ soil surface parameter measurements (moisture content and roughness) is used. The retrieval of soil...

The aim of this study is to assess the effects and interests of integrating remote-sensing-derived parameters (LAI, harvest and irrigation dates) in a crop model (PILOTE) that simulates vegetation growth for hay crops. The target variable is the prediction of Total Dry Matter (TDM) production in each of the three growth cycles. Two scenarios are em...

Mapping forest aboveground biomass (AGB) has become an important task, particularly for the reporting of carbon stocks and changes. AGB can be mapped using synthetic aperture radar data (SAR) or passive optical data. However, these data are insensitive to high AGB levels (>150 Mg/ha, and >300 Mg/ha for P-band), which are commonly found in tropical...

The behavior of the Ka-band backscattering coefficient at nadir and close-to-nadir angles for land applications is poorly documented. The measurements made during a ground-based campaign at Ka-band were performed at nadir and close-to-nadir angles over bare soils for different surface roughness and soil moisture conditions. The resulting backscatte...

Land monitoring using temporal series of Synthetic Aperture Radar (SAR) images requires radiometrically well calibrated sensors. In this paper, the radiometric stability of the new SAR Sentinel-1A "S-1A" sensor was first assessed by analyzing temporal variations of the backscattering coefficient (σ°) returned from invariant targets. Second, the rad...

LiDAR data has been successfully used to estimate forest parameters such as canopy heights and biomass. Major limitation of LiDAR systems (airborne and spaceborne) arises from their limited spatial coverage. In this study, we present a technique for canopy height mapping using airborne and spaceborne LiDAR data (from the Geoscience Laser Altimeter...

The aim of this study was to develop an inversion approach to estimate surface soil moisture from X-band SAR data over irrigated grassland areas. This approach simulates a coupling scenario between Synthetic Aperture Radar (SAR) and optical images through the Water Cloud Model (WCM). A time series of SAR (TerraSAR-X and COSMO-SkyMed) and optical (S...

Dans un contexte d’accroissement des tensions sur les ressources en eau, la recherche d’une meilleure productivité agricole de l’eau d’irrigation amène à optimiser les calendriers d’arrosage en fonction des états hydriques des sols et des stades de développement de la culture. La télédétection spatiale permet aujourd’hui de fournir des informations...

To develop an approach for estimating soil moisture and vegetation parameters in irrigated grasslands by coupling SAR C-band and optical data: neural network (NN) inversion technique

The retrieval of biophysical parameters of soil and vegetation using Synthetic Aperture Radar (SAR) images requires radiometrically well-calibrated sensors. In this paper, the radiometric quality of TerraSAR-X (TSX) and COSMO-SkyMed (CSK) constellation (four satellites: CSK1, CSK2, CSK3, and CSK4) was assessed. The analysis of the X-band SAR signal...

The objective of this study was to analyze the sensitivity of radar signals in the X-band in irrigated grassland conditions. The backscattered radar signals were analyzed according to soil moisture and vegetation parameters using linear regression models. A time series of radar (TerraSAR-X and COSMO-SkyMed) and optical (SPOT and LANDSAT) images was...

The objective of this study was to analyze the sensitivity of radar signal in X-band to irrigated grassland soil conditions. Time series of radar (TerraSAR-X and Cosmo-SkyMed) images were acquired at a high temporal frequency in 2013 over a small agricultural region in South Eastern France. Simultaneously to satellite data acquisitions, ground meas...