Stephanie Delalieux

Flemish Institute for Technological Research | VITO · Research Group for Earth Observation

Red palm weevil (RPW) is widely considered a key pest of palms, creating extensive damages to the date palm trunk that inevitably leads to palm death if no pest eradication is done. This study evaluates the potential of a remote sensing approach for the timely and reliable detection of RPW infestation on the palm canopy. For two consecutive years,...

Phoenix palms cover more than 1.3 million hectares in the Mediterranean, Middle East, and North Africa regions and they represent highly valued assets for economic, environmental, and cultural purposes. Despite their importance, information on the number of palm trees and the palm distribution across different scenes is difficult to obtain and, the...

Controlling fire blight in pear production areas depends strongly on regular visual inspections of pome fruit orchards, nurseries and other hosts of Erwinia amylovora. In addition, these inspections play an essential role in delineating fire blight free production areas, which has important implications for fruit export. However, visual monitoring...

High quality fruit production requires the regulation of the crop load on fruit trees by reducing the number of flowers and fruitlets early in the growing season, if the bearing is too high. Several automated flower cluster quantification methods based on proximal and remote imagery methods have been proposed to estimate flower cluster numbers, but...

Early and precise spatio-temporal monitoring of tree vitality is key for steering management decisions in pome fruit orchards. Spaceborne remote sensing instruments face a tradeoff between spatial and spectral resolution, while manned aircraft sensor-platform systems are very expensive. In order to address the shortcomings of these platforms, this...

Combining multi-date and multi-instrument remote sensing imagery critically depends on precise coregistration. We present a set of methods to improve registration of image pairs. It builds up a misregistration model by area-based matching and uses the model to warp images to a reference. The challenge is to achieve good matching for images with ver...

In strawberry production, a balanced and accurate irrigation schedule is essential, because of the high sensitivity of strawberry plants to water deficits and waterlogging. The optimal irrigation management strategy can, however, only be obtained by an accurate crop monitoring system. To replace the current visual inspection methods, which are subj...

Nowadays, very lightweight hyperspectral cameras are realized using thin film interference filters. They allow efficient mapping from small UAS systems, opening up new markets e.g. in precision agriculture. Direct deposition of filter material on the detector array, a technique developed by imec, the Belgian research and innovation center in nano-e...

Nowadays, very lightweight hyperspectral cameras are realized using thin film interference filters. They allow efficient mapping from small UAS systems, opening up new markets e.g. in precision agriculture. Direct deposition of filter material on the detector array, a technique developed by imec, the Belgian research and innovation center in nano-e...

Appropriate management of (semi-)natural areas requires detailed knowledge of the ecosystems present and their status. Remote sensing can provide a systematic, synoptic view at regular time intervals, and is therefore often suggested as a powerful tool to assist with the mapping and monitoring of protected habitats and vegetation. In this study, we...

The ECOPLAN project developed a range of methods and tools that allow to integrate the scientific knowledge of ecosystem services in spatial planning. The ECOPLAN tools can be used at various stages of the planning process (analysis, vision, planning, implementation, evaluation). Tools can often be useful in multiple stages. The ECOPLAN tools have...

Agricultural field experiments are essential to acquire detailed information on the effects of fertilizers, cultivation methods, treatments and seed varieties on final crop yield. Comparative field trials on adjacent plots need to be monitored accurately and continuously. To complement and eventually replace ground observations, recent advances in...

This paper gives an overview of the new COmpact hyperSpectral Imaging (COSI) system recently developed at the Flemish Institute for Technological Research (VITO, Belgium) and suitable for remotely piloted aircraft systems. A hyperspectral dataset captured from a multirotor platform over a strawberry field is presented and explored in order to asses...

This paper gives an overview of the new COmpact hyperSpectral Imaging (COSI) system recently developed at the Flemish Institute for Technological Research (VITO, Belgium) and suitable for remotely piloted aircraft systems. A hyperspectral dataset captured from a multirotor platform over a strawberry field is presented and explored in order to asses...

This presentation gives an overview of the new COmpact hyperSpectral Imaging (COSI) system recently developed at the Flemish Institute for Technological Research (VITO, Belgium) and suitable for multirotor Remotely Piloted Aircraft Systems (RPAS) platforms. The camera is compact and lightweight, with a total mass of less than 500g including: an emb...

Worldwide, great effort is spent on agricultural field experiments. The effects of fertilizers, cultivation methods, treatments and seed varieties are tested through comparative trials on adjacent plots. The results are of immediate interest to farmers. Field trials are also vital to gather important scientific information, e.g. to assess the perfo...

Many applications require a timely acquisition of high spatial and spectral resolution remote sensing data. This is often not achievable since spaceborne remote sensing instruments face a tradeoff between spatial and spectral resolution, while airborne sensors mounted on a manned aircraft are too expensive to acquire a high temporal resolution. Thi...

The objective of this study was to use satellite imagery combined with field-based spectral analysis to assess the impacts of mining-related activities on vegetation around the smelter town of Karabash, South Ural Mountains of Russia. Time series analysis of normalized difference vegetation index (NDVI) and fraction of absorbed photosynthetically a...

Monitoring the conservation status of natural habitats is an essential aspect of effective conservation management. Not only data on habitat occurrence are needed, but also detailed information on the structural and functional characteristics of the habitat patches is crucial for an adequate conservation status assessment. Classification of hypersp...

Within the ImpactMin project, funded by the Framework Programme 7 of the European Commission, new methods for the environmental impact monitoring of mining operations are being developed. The objective of this study is to analyze the impact of mining on soil properties through assessment of the vegetation status using time series analysis of low re...

The three principal activities of the mineral resources mining industry - mining, mineral processing and metallurgical extraction - all produce waste. The environmental impact of these activities depends on many factors, in particular, the type of mining and the size of the operation. The effects of the mining (extraction) stage tend to be mainly l...

The value of hyperspectral imagery in agricultural management has been amply demonstrated. Despite this, image interpretation is often drastically impeded by changes in soil moisture content (SMC). Soil moisture variations dominate the spectral reflectance in the 350–2500-nm wavelength domain and affect the effectiveness of spectral indices used to...

Linear spectral mixture analysis (SMA) has been used extensively in remote sen-sing studies to estimate the sub-pixel composition of spectral mixtures. The lack of ability to account for sufficient temporal and spatial variability between and among ground component or endmember spectra has been acknowledged as a major shortcoming of conventional SM...

Natura 2000, an EU-wide network of nature protection areas, has as main objective the achievement or maintenance of a favorable conservation status of habitats protected by the EU Habitats directives. Within this framework, this study examines a strategy to characterize the status of heathland vegetation from airborne hyperspectral AHS data in the...

Removing soil moisture effects in spectral images is critical for agricultural remote sensing. Yet, current available soil moisture reflectance models fail to properly address subtly, yet significant, moisture induced reflectance changes within soils of the same texture class. The operational implementation of these models is as such limited, parti...

This poster presents a classification framework for the mapping of Natura 2000 heath land habitats, using airborne hyperspectral imagery. The majority of these habitats have the intrinsic property of a high heterogeneity in species composition. Consequently, straightforward mapping based on spectral reflectance, does not lead to satisfying results....

Straightforward mapping of detailed heathland habitat patches and their quality using remote sensing is hampered by (1) the intrinsic property of a high heterogeneity in habitat species composition (i.e. high intra-variability), and (2) the occurrence of the same species in multiple habitat types (i.e. low inter-variability). Mapping accuracy of de...

Habitat monitoring of designated areas under the EU Habitats Directive requires every 6 years information on area, range, structure and function for the protected (Annex I) habitat types. First results from studies on heathland areas in Belgium and the Netherlands show that hyperspectral imagery can be an important source of information to assist t...

Straightforward mapping of detailed heathland habitat patches and their quality using remote sensing is hampered by (1) the intrinsic property of a high heterogeneity in habitat species composition (i.e. high intra-variability), and (2) the occurrence of the same species in multiple habitat types (i.e. low inter-variability). Mapping accuracy of de...

Very few attempts have been made to qualify and quantify the contribution of fruits to the hyperspectral canopy signal. The interference of fruit may influence the effectiveness of spectral indices and radiative transfer models used to monitor leaf-related biochemical and biophysical parameters. In a series of experiments, the spectral characterist...

A Dorsiventral Leaf Model (DLM) is presented to simulate leaf radiative transfer. DLM was conceived as a plate model with a stochastic distribution of different groups of layers. Leaf asymmetry was modeled by assigning non-uniform distributions of pigments, water and dry matter to palisade and mesophyll layers and by simulating different amounts of...

Traditionally, spectral mixture analysis (SMA) fails to fully account for highly similar ground components or endmembers. The high similarity between weed and crop spectra hampers the implementation of SMA for steering weed control management practices. To address this problem, this paper presents an alternative SMA technique, referred to as Integr...

Apple scab causes significant losses in the production of this fruit. A timely and more site-specific monitoring and spraying of the disease could reduce the number of applications of fungicides in the fruit industry. The aim of this leaf-scale study therefore lies in the early detection of apple scab infections in a non-invasive and non-destructiv...

Accurate monitoring of spatial and temporal variation in tree cover provides essential information for steering management practices in orchards. In this light, the present study investigates the potential of Hyperspectral Mixture Analysis. Specific focus lies on a thorough study of non-linear mixing effects caused by multiple photon scattering. In...

Novel and existing hyperspectral vegetation indices were evaluated in this study, with the aim of assessing their utility for accurate tracking of leaf spectral changes due to differences in biophysical indicators caused by apple scab. Novel indices were extracted from spectral profiles by means of narrow-waveband ratioing of all possible two-band...

The accurate monitoring of the spatial and temporal variation in tree cover provides critical information for steering management practices in orchards. In this light, the present study investigates the potential of Hyperspectral Mixture Analysis. Specific focus is on non-linear mixing effects caused by multiple photon scattering. A novel conceptua...

A Dorsiventral Leaf Model (DLM) was constructed to simulate radiative transfer within leaves. DLM was conceived as a four layer plate model with a stochastic binomial distribution of different groups of layers that are either adjoint or separate by air spaces. This model structure allowed dorsiventral properties of leaves to be parameterized by an...

Radiative transfer (RT) models for canopies entail multiple implicit and explicit assumptions. In this case study six different commonly used assumptions were evaluated on a detailed virtual orchard model. This model was constructed in a physically based ray-tracing environment using detailed sub-models for the description of tree geometry, leaf an...

The least squares error (LSE) technique is frequently used to estimate abundance fractions in linear spectral mixture analysis (LSMA). The LSE is typically equally weighted for all wavebands, assuming equally important effects. This is, however, not always the case and therefore traditional LSMA often results in suboptimal fraction estimates. This...

The sub-pixel spectral contribution of background soils and shadows hampers the accurate site-specific monitoring of agricultural crop characteristics from aerial or satellite images. To address this problem, the present study combines measured in situ and hyperspectral data in an alternative unmixing algorithm. The proposed algorithm, referred to...

Hyperspectral canopy reflectance measurements are usually obtained under ambient solar illumination. In some specific cases, however, the use of artificial light is preferred. This raises issues, since artificial light is usually non‐parallel and non‐homogeneous over the area and height profile of the target. This study therefore attempts to addres...

An innovative index for LAI estimation over orchard canopies based on the combination of two near-infrared narrow wavebands (1050 nm and 1250 nm) is presented. The index is insensitive to physiological changes on the leaf level even under changing pheneological developmental stage. In the meantime, the index is highly sensitive for variations at th...

This paper presents the results of estimation of leaf chlorophyll concentration through model inversion, from hyperspectral imagery of artificially treated orchard crops. The objectives were to examine model inversion robustness under changing viewing conditions, and the potential of multi-angle hyperspectral data to improve accuracy of chlorophyll...

Traditionally, Spectral Mixture Analysis (SMA) fails to fully account for highly similar ground components or endmembers. The high similarity between weed and crop spectra therefore hampers the implementation of SMA for steering weed control management practices. To address this problem, the current study presents an alternative SMA technique, refe...

The use of hyperspectral approaches for early detection of plant stress caused by Venturia inaequalis (apple scab) was investigated to move towards more efficient and reduced application of pesticides, fertilizers or other crop management treatments in apple orchards. Apple leaves of the resistant cultivar, Rewena and the susceptible cultivar, Brae...

This research was conducted to assess the potential of hyperspectral indices to detect iron defi-ciency in capital-intensive multi-annual crop systems. A well-defined hyperspectral multi-layer dataset was constructed for a peach orchard in Zaragoza, Spain, consisting of hyperspectral measurements at various monitoring levels (leaf, crown, airborne)...

En: Remote Sensing for Agriculture, Ecosystems, and Hydrology VIII .--Proceedings of the International Society for Optical Engineering (SPIE), 11 September 2006 , Stockholm, Sweden A technique is presented for detecting vegetation crop nutrient stress from hyperspectral data. Experiments are conducted on peach trees. It is shown that nutrient defic...

Early detection of biotic and abiotic stresses and subsequent steering of agricultural systems using hyperspectral sensors potentially could contribute to the pro-active treatment of production-limiting factors. Venturia inaequalis (apple scab) is an important biotic factor that can reduce yield in apple orchards. Previous hyperspectral research fo...

The potential yield of (capital)-intensive multi-annual crops (e.g., fruit) is seldom harvested in real- ity. A targeted monitoring and modelling of the growth processes in such agricultural production systems could enable an early detection and treatment of production limiting factors, thereby opti- mising yield. In Belgium, as in all temperate re...

This paper studies the detection of vegetation stress in orchards via remote sensing. During previous research, it was shown that stress can be detected reliably on hyperspectral reflectances of the fresh leaves, using a generic wavelet based hyperspectral classification. In this work, we demonstrate the capability to detect stress from airborne/sp...

Vroegtijdige detectie van biotische en abiotische vegetatieve stress laat toe het beheer van commercieel belangrijke gewassen te optimaliseren. Efficiëntere bemesting en toediening van pesticides komt niet enkel de oogst, maar ook het milieu ten goede. Plantenziektes en nutriëntentekort beïnvloeden de fysiologische toestand en het daarmee verbonden...

Presented at the Airborne Imaging Spectroscopy Workshop, BruHyp 2006, 10 October 2006, Bruges, Belgium. This research was conducted to evaluate the potential and limitations of hyperspectral remote sensing to detect iron deficiency in capital-intensive multi-annual crop systems, e.g. peach orchards. The noted deficiency can be regarded as a proxy f...