Synergistic use of Sentinel-2 and UAV-derived data for plant fractional cover distribution mapping of coastal meadows with digital elevation models

Coastal wetlands provide a range of ecosystem services, yet they are currently under threat from global change impacts. Thus, their monitoring and assessment is vital for evaluating their status, extent and distribution. Remote sensing provides an excellent tool for evaluating coastal ecosystems, whether with small-scale studies using drones or national-/regional-/global-scale studies using satellite-derived data. This study used a fine-scale plant community classification of coastal meadows in Estonia derived from a multispectral camera on board unoccupied aerial vehicles (UAVs) to calculate the plant fractional cover (PFC) in Sentinel-2 MultiSpectral Instrument (MSI) sensor grids. A random forest (RF) algorithm was trained and tested with vegetation indices (VIs) calculated from the spectral bands extracted from the MSI sensor to predict the PFC. Additional RF models were trained and tested after adding a digital elevation model (DEM). After comparing the models, results show that using DEM with VIs can increase the prediction accuracy of PFC up to 2 times (R2 58%-70%). This suggests the use of ancillary data such as DEM to improve the prediction of empirical machine learning models, providing an appropriate approach to upscale local studies to wider areas for management and conservation purposes

A novel UAV-based approach for biomass prediction and grassland structure assessment in coastal meadows

Coastal meadows provide a wide range of ecosystem services worldwide. In order to better target conservation efforts in these ecosystems, it is necessary to develop highly accurate models that account for the spatial nature of ecosystem structure, processes and functions. In this study, above-ground biomass was predicted at very high spatial resolution in nine study sites in Estonia. A combination of UAV-derived datasets were used to produce vegetation indices and micro topographic models. A random forest algorithm was used to generate above-ground biomass maps and assess the contribution of each predictor variable. The model successfully predicted above-ground biomass at very high accuracies. Additionally, grassland structural heterogeneity was assessed using UAV-derived datasets and vegetation indices. The results were subsequently related to management history at each study site, showing that continuous, monospecific grazing management tends to simplify grassland structure, which could in turn reduce the supply of a key regulation and maintenance ecosystem services: nursery and reproduction habitat for waders. These results also indicate that UAV-based surveys can serve as reliable grassland monitoring tools and could aid in the development of site-specific management strategies

From UAV to PlanetScope: Upscaling fractional cover of an invasive species Rosa rugosa.

Invasive plant species pose a direct threat to biodiversity and ecosystem services. Among these, Rosa rugosa has had a severe impact on Baltic coastal ecosystems in recent decades. Accurate mapping and monitoring tools are essential to quantify the location and spatial extent of invasive plant species to support eradication programs. In this paper we combined RGB images obtained using an Unoccupied Aerial Vehicle, with multispectral PlanetScope images to map the extent of R. rugosa at seven locations along the Estonian coastline. We used RGB-based vegetation indices and 3D canopy metrics in combination with a random forest algorithm to map R. rugosa thickets, obtaining high mapping accuracies (Sensitivity = 0.92, specificity = 0.96). We then used the R. rugosa presence/absence maps as a training dataset to predict the fractional cover based on multispectral vegetation indices derived from the PlanetScope constellation and an Extreme Gradient Boosting algorithm (XGBoost). The XGBoost algorithm yielded high fractional cover prediction accuracies (RMSE = 0.11, R2 = 0.70). An in-depth accuracy assessment based on site-specific validations revealed notable differences in accuracy between study sites (highest R2 = 0.74, lowest R2 = 0.03). We attribute these differences to the various stages of R. rugosa invasion and the density of thickets. In conclusion, the combination of RGB UAV images and multispectral PlanetScope images is a cost-effective method to map R. rugosa in highly heterogeneous coastal ecosystems. We propose this approach as a valuable tool to extend the highly local geographical scope of UAV assessments into wider areas and regional evaluations

Machine learning classification and accuracy assessment from high-resolution images of coastal wetlands

High-resolution images obtained by multispectral cameras mounted on Unmanned Aerial Vehicles (UAVs) are helping to capture the heterogeneity of the environment in images that can be discretized in categories during a classification process. Currently, there is an increasing use of supervised machine learning (ML) classifiers to retrieve accurate results using scarce datasets with samples with non-linear relationships. We compared the accuracies of two ML classifiers using a pixel and object analysis approach in six coastal wetland sites. The results show that the Random Forest (RF) performs better than K-Nearest Neighbors (KNN) algorithm in the classification of pixels and objects and the classification based on pixel analysis is slightly better than the object-based analysis. The agreement between the classifications of objects and pixels is higher in Random Forest. This is likely due to the heterogeneity of the study areas, where pixel-based classifications are most appropriate. In addition, from an ecological perspective, as these wetlands are heterogeneous, the pixel-based classification reflects a more realistic interpretation of plant community distribution

Security analysis of a chaotic map-based authentication scheme for telecare medicine information systems

Many authentication schemes have been proposed for telecare medicine information systems (TMIS) to ensure the privacy, integrity, and availability of patient records. These schemes are crucial for TMIS systems because otherwise patients’ medical records become susceptible to tampering thus hampering diagnosis or private medical conditions of patients could be disclosed to parties who do not have a right to access such information. Very recently, Hao et al. proposed a chaotic map-based authentication scheme for telecare medicine information systems in a recent issue of Journal of Medical Systems. They claimed that the authentication scheme can withstand various attacks and it is secure to be used in TMIS. In this paper, we show that this authentication scheme is vulnerable to key-compromise impersonation attacks, off-line password guessing attacks upon compromising of a smart card, and parallel session attacks. We also exploit weaknesses in the password change phase of the scheme to mount a denial-of-service attack. Our results show that this scheme cannot be used to provide security in a telecare medicine information system

Artéria femoral profunda: uma opção como origem de fluxo para derivações infrageniculares Deep femoral artery: an option as inflow site in infragenicular bypasses

CONTEXTO: Na isquemia crítica, a artéria femoral profunda pode tornar-se a opção mais distal como origem de fluxo para derivações distais em casos de oclusão da origem da artéria femoral superficial associada a prega inguinal hostil. OBJETIVO:Avaliar, retrospectivamente, a artéria femoral profunda como doadora de fluxo para derivações infrageniculares. MÉTODOS: De 2000 a 2005, 129 derivações infrageniculares apresentaram anastomose proximal nas artérias femorais, comum (40), superficial (72) e profunda (17). O presente estudo teve como foco a artéria femoral profunda, e suas indicações foram: prega inguinal hostil (seis casos), limite da extensão do substituto (seis casos) e ambos os fatores (outros cinco casos). Foram abordadas a primeira e a segunda porção em 12 casos e a terceira porção em cinco casos. As cirurgias foram secundárias em 47% dos casos, e os substitutos utilizados foram veias do membro superior em 11 casos, safena interna em cinco e safena externa em um caso. RESULTADOS: No total dos enxertos (129), as estimativas de perviedade primária e salvamento do membro foram: 68,0% e 84,7%, respectivamente, com erro padrão (EP) aceitável (0,1) em 36 meses. Quando o grupo foi estratificado, as artérias femorais comum, superficial e profunda apresentaram resultados comparáveis de perviedade primária (63,3, 70,2 e 64,7%; p = 0,63) e salvamento do membro (83,1, 82,4 e 92,3%; p = 0,78). A perviedade dos enxertos com origem nas porções proximal e distal da artéria femoral profunda, bem como das cirurgias primárias e secundárias, foram comparáveis, sem diferença estatística significante (p = 0,89 e p = 0,77, respectivamente). CONCLUSÃO: A artéria femoral profunda mostrou ser acessível e efetiva como origem de fluxo de enxertos infrageniculares, com resultados satisfatórios de perviedade e salvamento do membro.<br>BACKGROUND: Deep femoral artery can be the most distal technical option as donor site in patients with critical limb ischemia presenting superficial artery occlusion and hostile groins. OBJECTIVE: To retrospectively assess the deep femoral artery as an inflow site for infragenicular bypass grafts. METHODS: From 2000 to 2005, 129 infragenicular bypass grafts with proximal anastomosis located in femoral arteries were performed. Forty were located in the common femoral artery (CFA), 72 in the superficial femoral artery (SFA) and 17 in the deep femoral artery (DFA). Indications for using the DFA as inflow were hostile groin (six cases), limited arterial substitute length (six cases) or both (five cases). Anastomosis site was located in the first or second portion in 12 cases, and in the third in five cases. The surgery was secondary in 47% of the cases, and the arterial substitutes used were arm veins (11), greater saphenous vein (five) and lesser saphenous vein (one). RESULTS: Primary patency and limb salvage rates were 68.0 and 84.7%, respectively, with acceptable standard error (0.1) in 36 months. The results of patency divided by inflow artery were similar (CFA, 63.3%; SFA, 70.2%; DFA 64.7%; p = 0.63), as well as limb salvage rates (CFA, 83.1%; SFA, 82.4%; DFA 92.3%; p = 0.78). Analyzing the deep femoral group, no difference of patency rates was observed when the anastomotic site was compared (proximal vs. distal portions of the DFA) or between patients with or without previous grafts. (p = 0.89 and 0.77, respectively). CONCLUSION: Deep femoral artery is a feasible and effective option as donor site for infragenicular bypass grafts, with satisfactory patency and limb salvage rates