Philippe Lejeune

Bio: Philippe Lejeune is an academic researcher from Gembloux Agro-Bio Tech. The author has contributed to research in topics: Forest inventory & Riparian zone. The author has an hindex of 39, co-authored 295 publications receiving 6372 citations. Previous affiliations of Philippe Lejeune include Free University of Brussels & University of Liège.

Are unmanned aircraft systems (UASs) the future of wildlife monitoring? A review of accomplishments and challenges

Abstract: Regular monitoring of animal populations must be established to ensure wildlife protection, especially when pressure on animals is high. The recent development of drones or unmanned aircraft systems (UASs) opens new opportunities. UASs have several advantages, including providing data at high spatial and temporal resolution, providing systematic, permanent data, having low operational costs and being low-risk for the operators. However, UASs have some constraints, such as short flight endurance. We reviewed studies in which wildlife populations were monitored by using drones, described accomplishments to date and evaluated the range of possibilities UASs offer to provide new perspectives in future research. We focused on four main topics: 1) the available systems and sensors; 2) the types of survey plan and detection possibilities; 3) contributions towards anti-poaching surveillance; and 4) legislation and ethics. We found that small fixed-wing UASs are most commonly used because these aircraft provide a viable compromise between price, logistics and flight endurance. The sensors are typically electro-optic or infrared cameras, but there is the potential to develop and test new sensors. Despite various flight plan possibilities, mostly classical line transects have been employed, and it would be of great interest to test new methods to adapt to the limitations of UASs. Detection of many species is possible, but statistical approaches are unavailable if valid inventories of large mammals are the purpose. Contributions of UASs to anti-poaching surveillance are not yet well documented in the scientific literature, but initial studies indicate that this approach could make important contributions to conservation in the next few years. Finally, we conclude that one of the main factors impeding the use of UASs is legislation. Restrictions in the use of airspace prevent researchers from testing all possibilities, and adaptations to the relevant legislation will be necessary in future.

A Photogrammetric Workflow for the Creation of a Forest Canopy Height Model from Small Unmanned Aerial System Imagery

Abstract: The recent development of operational small unmanned aerial systems (UASs) opens the door for their extensive use in forest mapping, as both the spatial and temporal resolution of UAS imagery better suit local-scale investigation than traditional remote sensing tools. This article focuses on the use of combined photogrammetry and “Structure from Motion” approaches in order to model the forest canopy surface from low-altitude aerial images. An original workflow, using the open source and free photogrammetric toolbox, MICMAC (acronym for Multi Image Matches for Auto Correlation Methods), was set up to create a digital canopy surface model of deciduous stands. In combination with a co-registered light detection and ranging (LiDAR) digital terrain model, the elevation of vegetation was determined, and the resulting hybrid photo/LiDAR canopy height model was compared to data from a LiDAR canopy height model and from forest inventory data. Linear regressions predicting dominant height and individual height from plot metrics and crown metrics showed that the photogrammetric canopy height model was of good quality for deciduous stands. Although photogrammetric reconstruction significantly smooths the canopy surface, the use of this workflow has the potential to take full advantage of the flexible revisit period of drones in order to refresh the LiDAR canopy height model and to collect dense multitemporal canopy height series.

Unmanned aerial survey of elephants.

Abstract: The use of a UAS (Unmanned Aircraft System) was tested to survey large mammals in the Nazinga Game Ranch in the south of Burkina Faso. The Gatewing ×100™ equipped with a Ricoh GR III camera was used to test animal reaction as the UAS passed, and visibility on the images. No reaction was recorded as the UAS passed at a height of 100 m. Observations, made on a set of more than 7000 images, revealed that only elephants (Loxodonta africana) were easily visible while medium and small sized mammals were not. The easy observation of elephants allows experts to enumerate them on images acquired at a height of 100 m. We, therefore, implemented an aerial strip sample count along transects used for the annual wildlife foot count. A total of 34 elephants were recorded on 4 transects, each overflown twice. The elephant density was estimated at 2.47 elephants/km2 with a coefficient of variation (CV%) of 36.10%. The main drawback of our UAS was its low autonomy (45 min). Increased endurance of small UAS is required to replace manned aircraft survey of large areas (about 1000 km of transect per day vs 40 km for our UAS). The monitoring strategy should be adapted according to the sampling plan. Also, the UAS is as expensive as a second-hand light aircraft. However the logistic and flight implementation are easier, the running costs are lower and its use is safer. Technological evolution will make civil UAS more efficient, allowing them to compete with light aircraft for aerial wildlife surveys.

Methylene blue administration in septic shock: A clinical trial

Abstract: Objective A release of nitric oxide has been incriminated in the cardiovascular alterations of septic shock. Since guanylate cyclase is the target enzyme in the endothelium-dependent relaxation mediated by nitric oxide, we studied the acute effects of methylene blue, a potent inhibitor of guanylate

Modern Applied Statistics With S

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Remote Sensing And Image Interpretation

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Improved allometric models to estimate the aboveground biomass of tropical trees

Abstract: Terrestrial carbon stock mapping is important for the successful implementation of climate change mitigation policies. Its accuracy depends on the availability of reliable allometric models to infer oven-dry aboveground biomass of trees from census data. The degree of uncertainty associated with previously published pantropical aboveground biomass allometries is large. We analyzed a global database of directly harvested trees at 58 sites, spanning a wide range of climatic conditions and vegetation types (4004 trees ≥ 5 cm trunk diameter). When trunk diameter, total tree height, and wood specific gravity were included in the aboveground biomass model as covariates, a single model was found to hold across tropical vegetation types, with no detectable effect of region or environmental factors. The mean percent bias and variance of this model was only slightly higher than that of locally fitted models. Wood specific gravity was an important predictor of aboveground biomass, especially when including a much broader range of vegetation types than previous studies. The generic tree diameter-height relationship depended linearly on a bioclimatic stress variable E, which compounds indices of temperature variability, precipitation variability, and drought intensity. For cases in which total tree height is unavailable for aboveground biomass estimation, a pantropical model incorporating wood density, trunk diameter, and the variable E outperformed previously published models without height. However, to minimize bias, the development of locally derived diameter-height relationships is advised whenever possible. Both new allometric models should contribute to improve the accuracy of biomass assessment protocols in tropical vegetation types, and to advancing our understanding of architectural and evolutionary constraints on woody plant development.

Inhaled Nitric Oxide for the Adult Respiratory Distress Syndrome

Abstract: Background The adult respiratory distress syndrome is characterized by pulmonary hypertension and right-to-left shunting of venous blood. We investigated whether inhaling nitric oxide gas would cause selective vasodilation of ventilated lung regions, thereby reducing pulmonary hypertension and improving gas exchange. Methods Nine of 10 consecutive patients with severe adult respiratory distress syndrome inhaled nitric oxide in two concentrations for 40 minutes each. Hemodynamic variables, gas exchange, and ventilation-perfusion distributions were measured by means of multiple inert-gas-elimination techniques during nitric oxide inhalation; the results were compared with those obtained during intravenous infusion of prostacyclin. Seven patients were treated with continuous inhalation of nitric oxide in a concentration of 5 to 20 parts per million (ppm) for 3 to 53 days. Results Inhalation of nitric oxide in a concentration of 18 ppm reduced the mean (±SE) pulmonary-artery pressure from 37 ±3 mm Hg to 30 ±2...