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Aims: Given the inherent relationship between topography and land-use history in certain areas, we aimed at separating and estimating their relative contributions to the syntaxonomic and structural differentiation of the calcareous, semi-dry grassland communities. Study area: Western Cluj Hills (Transylvania, Romania). Methods: Exhaustive surveys of all vascular plant species were performed in 14 plots of 25 m2 each randomly distributed among two contrasting habitats i.e., recent grasslands recovered from former crops on hill ridges (HR) and ancient grasslands on sunny hillslopes (SS). Multivariate analyses (direct ordination) and generalised regressions were used to estimate the effects of terrain slope and grassland continuity on species composition, richness and guild proportions. Results: A statistically significant compositional dissimilarity was detected between the two groups of grassland communities, which were assigned to different plant associations: Festuco rupicolae-Brachypodietum pinnati (relatively more mesophilous) and Carici humilis-Brachypodietum pinnati (relatively more xerophilous). Total species richness and the fractions of species tolerant of drought/nutrient scarcity increased whereas the proportion of N-fixing species decreased steadily along the slope gradient. The proportion of short-lived ruderals (therophytes) was significantly larger in the recent grasslands, but was not affected by the terrain declivity. The finer plant specialisation allowed for higher species packing in the open SS grasslands, whereas intense asymmetric competition for light probably prevented the establishment of small, shade-intolerant species in the closed, more fertile HR grasslands. Conclusions: The difference in terrain slope was one of the main factors leading to the observed structural differentiation, whereas grassland continuity had a lower but not negligible contribution to compositional variation. To a large extent, ours results confirm the previous findings and provide further evidence of patterns induced by both land topography and traditional management continuity in structuring the calcareous, semi-dry grasslands. [ABSTRACT FROM AUTHOR]

Background: Wildfires can have detrimental impacts on the environment and urban structures when they spread from wildland areas. Aims: In this work, a numerical study was performed to investigate the effect of downslope terrain on fire-induced flows in the presence of a building structure. Fires with intensities of 4 and 15 MW m−1 were considered on inclined terrain with downslope angles varying from 0° to −30°, and wind speeds of 6 and 12 m s−1. Methods: Simulations were conducted using a large eddy simulation (LES) solver, implemented in the open-source platform FireFOAM. Key results: The results were validated with experimental measurements of a full-scale building model. Results show that at a wind velocity of 12 m s−1, structures on steeper downslope terrains are at higher risk of wildfire damage, whereas at a constant wind velocity of 6 m s−1, these structures are at a lower risk. Conclusions: The outcomes of the study highlight the physical effect of sloped terrain on buildings downwind of a line fire. Implications: The results from this study can be used to evaluate the validity of risk management measures including building standards and asset protection zones and can better inform ways of improving these measures. Numerical simulations were used to investigate the impacts of wind, fire intensity and downslope inclination interactions on the heat exposure of an idealised building structure. At higher wind speeds, buildings on steeper downslopes were at higher risk of wildfire impacts. These results are at odds with current Australian building standards. [ABSTRACT FROM AUTHOR]

Changes in topography, such as terrain elevation and slope, are an important source of landscape complexity influencing the ecology of animals, particularly in mountainous landscapes. In such landscapes animals navigate changes in elevation and slope in their daily movement. Despite the importance of topographic variation, studies of animal ecology in mountainous landscapes tend not to explicitly consider those effects on species detection. We deployed a broad‐extent, coarse resolution camera‐trapping system across a landscape with considerable complexity and quantified the influence of topographic variables on detection probability conditional on occurrence for multiple mammal species. Specifically, we examined the fine‐scale effects of terrain steepness and topographic position (i.e. ridges, mid‐slopes or valleys) on detection probability for 14 mammal species at camera‐traps. We found that detection probability increased on gently sloping terrain for six species and decreased on the steepest slopes sampled for three of these species and three additional species. Among four other mammal species, detection probability changed according to local topographic position though the directionality of these responses varied among these species. Several species, primarily meso‐carnivores as well as larger‐bodied species, like mule deer and black bears, were more detectable on gentle slopes than flat terrain. This pattern suggests that many species may use moderately steep terrain for the resources or heterogeneity they provide. Topographic position had comparatively less effect on species detection probabilities, suggesting that this variable does not have a strong effect on fine‐scale space use of animal species in mountainous regions. These relationships suggest that researchers should consider local terrain when siting camera traps in mountainous landscapes and analyzing survey data from such landscapes. Studies that compare the detection of mammal species at cameras deployed in close proximity will improve our understanding of fine‐scale topographic effects on mammal movement and detection. [ABSTRACT FROM AUTHOR]

The vertical structure of forests provides important parameters for estimating aboveground biomass (AGB) and it can be measured by lidar sensors. The Global Ecosystem Dynamics Investigation (GEDI) full-waveform lidar sensor collects data systematically over the Earth's surface from the International Space Station. Since GEDI became operational, it has collected billions of ∼25-m diameter footprints. This massive dataset has been used to create higher level gridded and non-grided products. However, GEDI's ∼25-m footprints can be subject to errors associated with effects of geolocation, terrain slope, and beam sensitivity, among others, which are likely transferred to the downstream products. This study aims to (1) evaluate the effect of beam sensitivity and terrain slope on the accuracy of relative heights (RH) of GEDI product L2A version 2 through comparison with discrete-return airborne lidar data collected over transects in the Brazilian Amazon Forest biome, (2) assess GEDI's geolocation uncertainty and investigate its combined effects with beam sensitivity and terrain slope, and (3) re-evaluate beam sensitivity and terrain slope effects on the GEDI L2A RHs using footprints that were geolocation-adjusted through a simple novel approach. The analysis separates GEDI footprints by acquisition time, i.e., daytime, nighttime, and combined (all-data). The discrete-return airborne lidar point clouds are used to derive terrain slope within the GEDI footprints and to simulate GEDI waveforms and derive RHs comparable to the GEDI L2A product. Results indicate that terrain slope only causes significant effects on GEDI data collected during daytime because solar radiation affects waveform signal-to-noise ratio. Beam sensitivity causes significant effects on nighttime and all-data GEDI L2A RHs. If geolocation uncertainty is considered, the effects of beam sensitivity and terrain slope have just minor changes. Geolocation-adjusted data continue showing significant effects on nighttime and all-data RH differences caused by beam sensitivity but produce unbiased results. This study improves the understanding of how beam sensitivity, terrain slope, and their combined effect with geolocation uncertainty may affect the GEDI L2A RH collected over the Brazilian Amazon forest during daytime and nighttime.

The aim of the study was to present new technologies that are useful for obtaining spatial information on real estate and integrating the data with existing databases maintained by public administration agencies. The technologies presented include the use of GIS tools combined with vector data representing cadastral parcels, and raster data acquired by LiDAR technology. The study also employs descriptive data containing transactional information. The application of these new tools for obtaining spatial information provides real estate market operators with additional data that allows for more reliable market analysis. The methodology of this work has been divided into two parts, the first part related to the creation of a real estate database as a reference for the acquisition of spatial data. The second part was dedicated to the acquisition, processing and analysis of spatial conditions in the study area. The study used the data on transactions to determine the parcels for which data on elevation situation were acquired. LiDAR data was then applied to the determined parcels to generate the DTM. The obtained terrain elevation model was processed by raster tools, which created maps of slope and maps of aspect. Currently the data on the features of properties found in real estate price registers maintained by public administration agencies are becoming more accessible in result of the ongoing digitisation of administrative offices in Poland. However, these data do not contain information on slope and aspect -- two real estate features that are crucial for surveying areas with varied relief. The presented analysis draws attention to new ways of acquiring spatial data and integrating it with existing databases. Finding ways to integrate data obtained from public administration agencies with modern geographic information systems (GIS) would improve the work not only of valuers, but also of many other real estate professionals (e.g. brokers, developers, bank analysts). [ABSTRACT FROM AUTHOR]

Forest density affects the inversion of forest height by influencing the penetration and attenuation of synthetic aperture radar (SAR) signals. Traditional forest height inversion methods often fail in low-density forest areas. Based on L-band single-baseline polarimetric SAR interferometry (PolInSAR) simulation data and the BioSAR 2008 data, we proposed a forest height optimization model at the stand scale suitable for various forest densities. This optimization model took into account shortcomings of the three-stage inversion method by employing height errors to represent the mean penetration depth and SINC inversion method. The relationships between forest density and extinction coefficient, penetration depth, phase, and magnitude were also discussed. In the simulated data, the inversion height established by the optimization method was 17.35 m, while the RMSE value was 3.01 m when the forest density was 100 stems/ha. This addressed the drawbacks of the conventional techniques including failing at low forest density. In the real data, the maximum RMSE of the optimization method was 2.17 m as the stand density increased from 628.66 stems/ha to 1330.54 stems/ha, showing the effectiveness and robustness of the optimization model in overcoming the influence of stand density on the inversion process in realistic scenarios. This study overcame the stand density restriction on L-band single baseline PolInSAR data for forest height estimation and offered a reference for algorithm selection and optimization. The technique is expected to be extended from the stand scale to a larger area for forest ecosystem monitoring and management. [ABSTRACT FROM AUTHOR]

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The combined effects of percent slope and fire intensity of a wind driven line fire on an idealized building has been numerically investigated in this paper. The simulations were done using the large eddy simulation (LES) solver of an open source CFD toolbox called FireFOAM. A set of three fire intensity values representing different heat release rates of grassland fuels on different inclined fuel beds have been modeled to analyze the impact of factors, such as fuel and topography on wind-fire interaction of a built area. An idealized cubic structure representing a simplified building was considered downstream of the fire source. The numerical results have been verified with the aerodynamic measurements of a full-scale building model in the absence of fire effects. There is a fair consistency between the modeled findings and empirical outcomes with maximum error of 18%, which acknowledge the validity and precision of the proposed model. The results show that concurrent increase of fire intensity and terrain slope causes an expansion of the surface temperature of the building which is partially due to the increase of flame tilt angle upslope on the hilly terrains. In addition, increasing fire intensity leads to an increase in the flow velocity, which is associated with the low-pressure area observed behind the fire front. Despite limitations of the experimental results in the area of wind-fire interaction the result of the present work is an attempt to shed light on this very important problem of fire behavior prediction. This article is a primary report on this subject in CFD modeling of the collective effects of fire intensity and sloped terrain on wind driven wildfire and its interaction on buildings. [ABSTRACT FROM AUTHOR]

In recent decades, the feasibility of using terrestrial laser scanning (TLS) in forest inventories was investigated as a replacement for time-consuming traditional field measurements. However, the optimal acquisition of point clouds requires the definition of the minimum point density, as well as the sensor positions within the plot. This paper analyzes the effect of (i) the number and distribution of scans, and (ii) the point density on the estimation of seven forest parameters: above-ground biomass, basal area, canopy base height, dominant height, stocking density, quadratic mean diameter, and stand density index. For this purpose, 31 combinations of TLS scan positions, from a single scan in the center of the plot to nine scans, were analyzed in 28 circular plots in a Mediterranean forest. Afterwards, multiple linear regression models using height metrics extracted from the TLS point clouds were generated for each combination. In order to study the influence of terrain slope on the estimation of forest parameters, the analysis was performed by using all the plots and by creating two categories of plots according to their terrain slope (slight or steep). Results indicate that the use of multiple scans improves the estimation of forest parameters compared to using a single one, although using more than three to five scans does not necessarily improves the accuracy. Moreover, it is also shown that lower accuracies are obtained in plots with steep slope. In addition, it was observed that each forest parameter has a strategic distribution depending on the field of view of the TLS. Regarding the point density analysis, the use of 1% to 0.1% (≈136 points·m−2) of the initial point cloud density (≈37,240.86 points·m−2) generates an R2adj difference of less than 0.01. These findings are useful for planning more efficient forest inventories, reducing acquisition and processing time as well as costs. [ABSTRACT FROM AUTHOR]

This paper presents the results of determining slope values using seven different methods for different resolutions: 1, 5, 10, 30, 90 meters for the Bystra catchment area. After calculating the slopes using different methods for different resolutions, the following slope ranges were created: 0.00°-2.99°, 3.00°-5.99°, 6.00°-9.99°, 10.00°-14.99° and ≥15° into which the corresponding pixels were included. The results of slope calculations were compared with geodetic field measurements of slopes in the vicinity of Esterka castle in Bochotnica, which is located in the Bystra catchment area. It was found that the good reproduction of the actual terrain relief, represented by the 1 m resolution Digital Terrain Model (DTM), deteriorates significantly starting from 30 m resolution. The method for determining terrain slopes that most accurately represents the true relief variability is the 2nd Degree Polynomial Adjustment method (Zevenbergen et al., 1987). The results of the analyses are crucial for determining the minimum quality of DTM data. In this study, high resolution data (1 m, 5 m, 10 m) were found to be suitable for analysis and interpretation of terrain slopes in a small catchment. The results of the study show what resolution of DTM should be used for other studies: morphometric, geomorphological or hydrological of small catchments, where the quality of results is important e.g. in accurate water balance analysis of catchments or soil erosion analysis in agriculture. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate the TOPODATA Digital Elevation Model (DEM) as a source of relevant altimetric information for urban cycling planning. A case study was conducted in the city of Bariri-SP. The Cartographic Accuracy Standard of Digital Cartographic Products (PEC-PCD), assessed by comparing the TOPODATA altitudes with homologous altitudes surveyed by a precise satellite method (GNSS), suggests that the DEM may not be adequate for phases of cycling planning that require greater detailing of the elements to be designed. A moderate to strong positive spatial autocorrelation was observed between the DEM errors. Regarding its usability for estimating the average slopes of the road segments, however, the results suggest that TOPODATA average slopes do not differ statistically from those estimated with field-surveyed data and, for the two criteria adopted for acceptable gradient lengths for cycling, more than 82% of the road segments were classified similarly using both sources of information.

Background: Previous investigations carried out in ultramafic habitats emphasized the greater importance of site conditions over soil toxic metal content for vegetation composition. Very little is known about the floristic structure of the Southern Carpathian ultramafic grasslands and there is no information on the local environmental drivers of their composition and coenotic features. Here, we aim to fill these knowledge gaps by referring to similar phytocoenoses described in the Balkan Peninsula and central Europe. In particular, we searched for: (i) floristic and ecological patterns supporting the classification and taxonomic assignment of these grasslands, and (ii) simple relationships between serpentine vegetation characteristics and its physiographic environment. A total of 120 phytosociological relevés, of which 52 performed in the Southern Carpathians, were analysed through cluster, ordination and regression procedures. Results: Despite some floristic similarities with their Balkan counterparts, the Southern Carpathian ultramafic grasslands were clustered into four distinct groups, which were assigned to as many new syntaxa: Plantago serpentinae–Armerietum halleri, Asplenio serpentini–Achnatheretum calamagrostis, Minuartio frutescentis–Plantaginetum holostei and Sileno saxifragae–Plantaginetum holostei. The latter was best individualised through the occurrence of several Carpathian endemic taxa. The first two ordination axes were significantly related with the terrain slope/presence of xerophilous species and respectively, with site elevation/presence of calcifugous species. The total plant cover showed a unimodal relationship with respect to site elevation. While controlling for the effect of the sampled area, species richness showed a unimodal response to both elevation and slope of the terrain, although their effects were not singular. Conclusions: The syntaxonomic distinctiveness of the Southern Carpathian ultramafic grasslands is mainly supported by their overall species composition rather than regional differential species. The main limiting factors driving the composition, cover and species richness of all studied ultramafic grasslands are the water deficit at low elevation and on steep slopes, and the low soil fertility at higher elevations. Our results confirm the previous findings according to which physiographic conditions and, to a lesser extent, soil base nutrients are more important than heavy metal concentrations in structuring the ultramafic vegetation. [ABSTRACT FROM AUTHOR]

Land fragmentation is one of the most important factors hindering the mechanization and scale of agriculture. To further alleviate the negative impact of arable land fragmentation, a more accurate model for measuring arable land fragmentation is needed. Using 0.1 resolution UAV images and farm survey data, we obtained spatial and tenure data of farming land in Baidu Village through ArcGis and other software, and analyzed the results and correlations of farming plot area, plot shape and plot dispersion indicators in the study area. A road accessibility index that integrates terrain slope and road network is proposed to characterize the dispersion of land parcels for the first time, and is compared with two road accessibility models that do not take into account terrain slope and road network. The results show that the dispersion index of farm plots is the most influential indicator on the fragmentation of farm plots, followed by the area index of farm plots, and finally the shape index of farm plots; the new model of measuring the fragmentation of farm plots based on natural surface elements and road networks is closer to the real situation and more accurate in portraying the degree of fragmentation of farm plots.

The purpose of this study was to investigate the effects of flat and uphill cycling on critical power and the work available above critical power. Thirteen well-trained endurance athletes performed three prediction trials of 10-, 4- and 1-min in both flat (0.6%) and uphill (9.8%) cycling conditions on two separate days. Critical power and the work available above critical power were estimated using various mathematical models. The best individual fit was used for further statistical analyses. Paired t-tests and Bland-Altman plots with 95% limits of agreement were applied to compare power output and parameter estimates between cycling conditions. Power output during the 10- and 4-min prediction trial and power output at critical power were not significantly affected by test conditions (all at p>0.05), but the limits of agreement between flat and uphill cycling power output and critical power estimates are too large to consider both conditions as equivalent. However, power output during the 1-min prediction trial and the work available above critical power were significantly higher during uphill compared to flat cycling (p<0.05). The results of this investigation indicate that gradient affects cycling time-trial performance, power output at critical power, and the amount of work available above critical power. [ABSTRACT FROM AUTHOR]

The correct capture of forest operations information carried out in forest plantations can help in the management of mechanized harvesting timber. Proper management must be able to dimension resources and tools necessary for the fulfillment of operations and helping in strategic, tactical, and operational planning. In order to facilitate the decision making of forest managers, this work aimed to analyze the performance of machine learning algorithms in estimating the productivity of timber harvesters. As predictors of productivity, we used the availability of hours of machine use, individual mean volumes of trees, and terrain slopes. The dataset was composed of 144,973 records, carried out over a period of 28 months. We tested the predictive performance of 24 machine learning algorithms in default mode. In addition, we tested the performance of blending and stacking joint learning methods. We evaluated the model's fit using the root mean squared error, mean absolute error, mean absolute percentage error, and determination coefficient. After cleaning the initial database, we used only 1.12% to build the model. Learning by blending ensemble stood out with a determination coefficient of 0.71 and a mean absolute percentage error of 15%. From the use of data from machine learning algorithms, it became possible to predict the productivity of timber harvesters. Testing a variety of machine learning algorithms with different dynamics contributed to the machine learning technique that helped us reach our goal: maximizing the model's performance by conducting experimentation. [ABSTRACT FROM AUTHOR]

• Modelling and characterization of fire-spotting generated fires through mesoscale factors. • Theoretical determination of the relationship between the flame length and the fire intensity. • Stating the Rate of Spread of the front in terms of the flame geometry. • Study of the role of the flame geometry and of the terrain slope on the emerging of fire-spotting generated fires. This is the second part of a series of two papers concerning fire-spotting generated fires. While, in the first part, we focus on the impact of macro-scale factors on the growth of the burning area by considering the atmospheric stability conditions, in the present study we focus on the impact of meso-scale factors by considering the effects of the flame geometry and terrain slope. First, we discuss the phenomenological power law that relates flame length and fireline intensity by reporting literature data, analysing a formula originally proposed by Albini, and deriving an alternative formula based on the energy conservation principle. Subsequently, we extend the physical fire-spotting parametrisation RandomFrontadopted in the first part by including flame geometry and slope. Numerical examples show that fire-spotting is affected by flame geometry and, therefore, cannot be neglected in simplified fire-spread models used in operational software codes for wildfire propagation. Meanwhile, we observe that terrain slope enhances the spread of a fire at a higher rate than the augmentation of fire-spotting generated fires, such that a rapid merging occurs among independent fires. [ABSTRACT FROM AUTHOR]

Objectives: The random volume over ground (RVoG) model is widely used in forest height inversion with polarimetric interferometric synthetic aperture radar (PolInSAR). The model assumes that the forest is a random uniform homogeneous body and the extinction coefficient in the model is a constant without considering the effects of forest vertical heterogeneity and terrain slope. This paper proposes a promising multi⁃baseline (MB) algorithm for forest height inversion based on a slope⁃RVoG (S⁃RVoG) model with linearly varying extinction. Methods: The effects of terrain slope and forest vertical heterogeneity on forest height inversion with the RVoG model are considered in the proposed algorithm. Firstly, the terrain slope is introduced to rectify the effective vertical wavenumber, and the S⁃RVoG model is derived on the basis of the basic RVoG model. Secondly, the linearly varying extinction coefficient, which is assumed to vary linearly with the forest height, is introduced into the S⁃RVoG model, and it can be solved by the Gaussian error function. Finally, MB PolInSAR datasets are used to solve the parameters of the S⁃RVoG model with linearly varying extinction, and the forest height can be obtained by the MB three⁃stage algorithm with coherence separation product criterion. The P⁃band F⁃SAR airborne PolInSAR datasets obtained by the 2016 AfriSAR campaign of the European Space Agency are selected for experimental verification. Results: The results of four MB algorithms, namely MB RVoG, MB S⁃RVoG, MB RVoG with linearly varying extinction, and MB S⁃RVoG with linearly varying extinction, are compared. The root mean square error (RMSE) and the relative error are used to evaluate the accuracy of the obtained forest height. (1) The forest height calculated by the MB RVoG algorithm is a significant overestimation, with RMSE of 6.57 m and relative error of 16.8%. (2) The RMSE of the MB S⁃RVoG algorithm is 5.97 m, and the relative error is 15.1%. The accuracy is improved by about 10% with the addition of terrain slope correction. (3) The MB RVoG algorithm with linearly varying extinction has RMSE of 4.71 m and relative error of 11.0%. Compared with the conventional MB RVoG algorithm, it improves the accuracy by about 28.3%. (4) The RMSE of the MB S⁃RVOG algorithm with linearly varying extinction is 4.27 m, and the relative error is 9.9%. Compared with the results of the MB RVoG algorithm and the MB S⁃RVOG algorithm, the accuracy is improved by about 35% and 28.4%, respectively. Conclusions: The RVoG model is widely used in PolInSAR forest height inversion. The MB S⁃RVOG algorithm with linearly varying extinction considers the effects of terrain slope and forest vertical heterogeneity simultaneously and introduces linearly varying extinction and terrain slope to correct the model, which makes up for the deficiency of the traditional RVoG model. The results show that the S⁃RVOG model with linearly varying extinction performs better in tropical forests with high forest density and great forest height. [ABSTRACT FROM AUTHOR]

In this study, a time-dependent investigation has been conducted to numerically analyze the impact of wind-driven surface fire on an obstacle located on sloped terrain downstream of the fire source. Inclined field with different upslope terrain angles of 0, 10, 20, and 30° at various wind-velocities have been simulated by FireFoam, which is a large eddy simulation (LES) solver of the OpenFOAM platform. The numerical data have been validated using the aerodynamic measurements of a full-scale building model in the absence of fire effects. The results underlined the physical phenomena contributing to the impact of varying wind flow and terrain slope near the fire bed on a built area. The findings indicated that under a constant heat release rate and upstream wind velocity, increasing the upslope terrain angle leads to an increase in the higher temperature areas on the ground near the building. It is also found that raising the inclined terrain slope angle from 0 to 30°, results in an increase in the integrated temperature on the surface of the building. Furthermore, by raising the terrain slope from 0 to 30°, the integrated temperature on the ground for the mentioned cases increases by 16%, 10%, and 13%, respectively. [ABSTRACT FROM AUTHOR]

Geomorphologic characteristics like altitude and terrain slope have an important but often neglected impact on light conditions in orchards. The study concentrated on the impact of altitude and terrain slope in combination with various colours of anti-hail nets (red, grey, blue, green and black) on the light and microclimate conditions in apple orchards. The results exhibit a large reduction of the photosynthetically active radiation (PAR) under the nets, most prominently under blue and red nets (reduction between 38.7 and 45.6%), while the impact of coloured nets on other microclimatic parameters (average air temperature, relative air humidity, temperature of dew point, wet-bulb temperature, heat index, minimum air temperature, maximum air temperature) remain irrelevant. The only consistent difference is an average of 2% increase of maximum air temperature under the blue net in comparison to other treatments. The use of the net also significantly reduce the wind speed (on average by 56.3%) and air flow (on average by 63.4%), and changes the distribution of precipitation in the orchard, most prominently in cases of heavy rain and drizzle. Regarding the orchard’s geomorphologic characteristics, a positive relationship exists between altitude and PAR.

The combined effects of percent slope and fire intensity of a wind driven line fire on an idealized building has been numerically investigated in this paper. The simulations were done using the large eddy simulation (LES) solver of an open source CFD toolbox called FireFOAM. A set of three fire intensity values representing different heat release rates of grassland fuels on different inclined fuel beds have been modeled to analyze the impact of factors, such as fuel and topography on wind-fire interaction of a built area. An idealized cubic structure representing a simplified building was considered downstream of the fire source. The numerical results have been verified with the aerodynamic measurements of a full-scale building model in the absence of fire effects. There is a fair consistency between the modeled findings and empirical outcomes with maximum error of 18%, which acknowledge the validity and precision of the proposed model. The results show that concurrent increase of fire intensity and terrain slope causes an expansion of the surface temperature of the building which is partially due to the increase of flame tilt angle upslope on the hilly terrains. In addition, increasing fire intensity leads to an increase in the flow velocity, which is associated with the low-pressure area observed behind the fire front. Despite limitations of the experimental results in the area of wind-fire interaction the result of the present work is an attempt to shed light on this very important problem of fire behavior prediction. This article is a primary report on this subject in CFD modeling of the collective effects of fire intensity and sloped terrain on wind driven wildfire and its interaction on buildings.

Forest density affects the inversion of forest height by influencing the penetration and attenuation of synthetic aperture radar (SAR) signals. Traditional forest height inversion methods often fail in low-density forest areas. Based on L-band single-baseline polarimetric SAR interferometry (PolInSAR) simulation data and the BioSAR 2008 data, we proposed a forest height optimization model at the stand scale suitable for various forest densities. This optimization model took into account shortcomings of the three-stage inversion method by employing height errors to represent the mean penetration depth and SINC inversion method. The relationships between forest density and extinction coefficient, penetration depth, phase, and magnitude were also discussed. In the simulated data, the inversion height established by the optimization method was 17.35 m, while the RMSE value was 3.01 m when the forest density was 100 stems/ha. This addressed the drawbacks of the conventional techniques including failing at low forest density. In the real data, the maximum RMSE of the optimization method was 2.17 m as the stand density increased from 628.66 stems/ha to 1330.54 stems/ha, showing the effectiveness and robustness of the optimization model in overcoming the influence of stand density on the inversion process in realistic scenarios. This study overcame the stand density restriction on L-band single baseline PolInSAR data for forest height estimation and offered a reference for algorithm selection and optimization. The technique is expected to be extended from the stand scale to a larger area for forest ecosystem monitoring and management.

Terrain slope and climate zone (heat zone) are important factors affecting land use zoning and agricultural production layout in mountainous areas. Using "weight grade method", a quantitative index of comprehensively evaluating terrain slope and climatic (thermal) conditions in mountainous areas was proposed: terra in-climate superiority degree (TCSD), and TCSD, terrain superiority degree (7SD), and climate superiority degree (CSD) in 129 counties (cities and districts) of Yunnan Province were measured and analyzed. The results showed that TCSD in 50.39% of counties of Yunnan Province was relatively better (levels I and II), and TCSD in 38.76% of counties was moderate (level III), while 'TCSD in 10. 85% of counties was relatively poorer (levels IV and V). [ABSTRACT FROM AUTHOR]

Background: Animal-attached devices can be used on cryptic species to measure their movement and behaviour, enabling unprecedented insights into fundamental aspects of animal ecology and behaviour. However, direct observations of subjects are often still necessary to translate biologging data accurately into meaningful behaviours. As many elusive species cannot easily be observed in the wild, captive or domestic surrogates are typically used to calibrate data from devices. However, the utility of this approach remains equivocal. Methods: Here, we assess the validity of using captive conspecifics, and phylogenetically-similar domesticated counterparts (surrogate species) for calibrating behaviour classification. Tri-axial accelerometers and tri-axial magnetometers were used with behavioural observations to build random forest models to predict the behaviours. We applied these methods using captive Alpine ibex (Capra ibex) and a domestic counterpart, pygmy goats (Capra aegagrus hircus), to predict the behaviour including terrain slope for locomotion behaviours of captive Alpine ibex. Results: Behavioural classification of captive Alpine ibex and domestic pygmy goats was highly accurate (> 98%). Model performance was reduced when using data split per individual, i.e., classifying behaviour of individuals not used to train models (mean ± sd = 56.1 ± 11%). Behavioural classifications using domestic counterparts, i.e., pygmy goat observations to predict ibex behaviour, however, were not sufficient to predict all behaviours of a phylogenetically similar species accurately (> 55%). Conclusions: We demonstrate methods to refine the use of random forest models to classify behaviours of both captive and free-living animal species. We suggest there are two main reasons for reduced accuracy when using a domestic counterpart to predict the behaviour of a wild species in captivity; domestication leading to morphological differences and the terrain of the environment in which the animals were observed. We also identify limitations when behaviour is predicted in individuals that are not used to train models. Our results demonstrate that biologging device calibration needs to be conducted using: (i) with similar conspecifics, and (ii) in an area where they can perform behaviours on terrain that reflects that of species in the wild. [ABSTRACT FROM AUTHOR]

• Solar tracking is a crucial task in efficiently harvesting solar power in a PV plant. • Horizontal Single-axis tracking systems require a precise estimation of its axis' orientation. • This methodology uses available data to accurately estimate the tracker's orientation. • This methodology estimates height differences in adjacent trackers. • The improve tracking and backtracking strategies increase production by 1%. Photovoltaic (PV) energy production is becoming a more significant part of the energy mix world-wide due to its clean origin, supportive and cost reductions. Therefore, it is increasingly important to develop methodologies to improve efficiency and reduce energy losses. Solar tracking is a way of increasing the irradiance over the PV field and, subsequently, boosting energy production. Both single-axis and double-axis tracking systems (SATS & DATS) are well known methods but both require not only a proper estimation of the sun's position but also precise knowledge of the tracker's position and orientation. Several factors (construction, design, configuration) can cause the values used to calculate the optimal tracking to be inaccurate, thus increasing production losses. This paper proposes a methodology to calculate the actual orientation of the trackers' axis based on the energy production of its associated strings. Additionally, it provides the height differences between adjacent trackers by detecting shading patterns. This information is key to defining more efficient tracking and backtracking strategies the avoid row-to-row shading and, overall increasing energy production. The proposed method is applied to a real 5 MW facility, identifying misalignments of several degrees in most trackers that were causing annual losses (1 %), not only due to inaccurate tracking but also row-to-row shading. [ABSTRACT FROM AUTHOR]

Gravimetric measurements allow monitoring mass transport in the Earth system and one example is temporal variations in the global water cycle including the cryosphere. Coupling gravity observations to the underlying processes requires modeling of the relevant mass elements. When observing the gravity field from space (i.e., by satellites), point mass models or simple spherical surface layers (mascons) are a reasonable choice. However, for terrestrial observations taken right on the surface of the relevant masses, precise modeling of the geometry of those mass elements and the related gravitational effects becomes crucial for the quality of the modeling and the correct interpretation of the results. In this study, two different modeling techniques are investigated, the right rectangular prism and the general polyhedron. Both approximations provide the possibility to analytically calculate the corresponding gravitational signal. Although modeling in terms of polyhedrons is numerically more complex and less efficient, the representation of the actual surface is superior as the inclined polyhedral surface fits much better to the actual topographic surface than the step function implied by rectangular prisms with horizontal top plane. The case study presented here is related to the gravimetric mass balance of a mountain glacier (Vernagtferner in the Ötz valley, Austria) where on the one hand high resolution digital terrain models (DTM of resolution 1 m × 1 m) are available, while on the other hand, the accuracy requirements are very high (on the level of 10−7 m/s2, i.e., 10 μGal). We evaluate first and second order derivatives of the gravitational potential induced by the melting of ice masses between epochs 2009 and 2016 at gravity sites on and off the actual glacier body. Furthermore, the relation of ground surface slope to the differences between the modeling approaches is investigated for a small part of the DTM, containing a variety of different slope regimes. Besides the original grid spacing, denser and coarser grids are also evaluated in order to examine the relation of the considered DTM resolution to the modeling differences. The modeling choice, the location of the computation points and the morphology of the mass distribution are the main factors that determine the quality of the results. The comparison of the two methods for the original 1 m resolution, provides differences up to 2.9 μGal for the vertical component of the attraction V z , 9.1 μGal/m for the gradient V zx , 4.6 μGal/m for V z y and 17.1 μGal/m for V zz. Coarser grid resolutions increase these values significantly, up to 500 μGal at specific locations, while grids denser than the 1 m resolution decrease them for about 48%. • Gravitational effect due to ice melting of Vernagtferner glacier during 2009–2016 is evaluated analytically. • Prism and polyhedral modeling applied for gravitational effects at gravity stations situated on and around the glacier. • The difference between the two techniques defines a range well inside the measurement accuracy of terrestrial gravimeters. [ABSTRACT FROM AUTHOR]

The correct capture of forest operations information carried out in forest plantations can help in the management of mechanized harvesting timber. Proper management must be able to dimension resources and tools necessary for the fulfillment of operations and helping in strategic, tactical, and operational planning. In order to facilitate the decision making of forest managers, this work aimed to analyze the performance of machine learning algorithms in estimating the productivity of timber harvesters. As predictors of productivity, we used the availability of hours of machine use, individual mean volumes of trees, and terrain slopes. The dataset was composed of 144,973 records, carried out over a period of 28 months. We tested the predictive performance of 24 machine learning algorithms in default mode. In addition, we tested the performance of blending and stacking joint learning methods. We evaluated the model’s fit using the root mean squared error, mean absolute error, mean absolute percentage error, and determination coefficient. After cleaning the initial database, we used only 1.12% to build the model. Learning by blending ensemble stood out with a determination coefficient of 0.71 and a mean absolute percentage error of 15%. From the use of data from machine learning algorithms, it became possible to predict the productivity of timber harvesters. Testing a variety of machine learning algorithms with different dynamics contributed to the machine learning technique that helped us reach our goal: maximizing the model’s performance by conducting experimentation.

BACKGROUND: The terrain slope and field altitude where the plant is cultivated influence the composition of coffee cherries. The aim of this study was to analyze the effects of different levels of altitude and terrain slope on the Coffea canephora cherries, as well as on the quality of the final beverage. C. canephora harvested in fields with 300 and 600 m altitude and with southeast‑ and northwest‐facing slopes was evaluated. RESULTS: Lower pH values were observed for cherries cultivated at higher altitudes. The highest percentage of soluble solids (525.00 g kg−1) was found on northwest‐facing slopes at 300 m. The highest values of phenolic compounds were observed at 600 m. Significant differences were found in the moisture of coffee cherries grown in different terrain slope and in the fiber content at different altitudes. The results do not enable us to conclude how the altitude and terrain slope influence the mineral content of cherries. Acidity, proteins, lipids, and carbohydrates were not influenced by altitude or terrain slope. The scores of cup quality were significantly affected by the altitude but not by the terrain slope. Coffees from cherries harvested in fields with 600 m altitude obtained the higher scores. CONCLUSION: Results show that altitude and terrain slope influence some compounds of coffee fruits, whereas others remain unaffected. The findings are important because, during coffee fruits processing, these compounds are used to produce others that will have an influence on the bean and coffee beverage quality. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, a time-dependent investigation has been conducted to numerically analyze the impact of wind-driven surface fire on an obstacle located on sloped terrain downstream of the fire source. Inclined field with different upslope terrain angles of 0, 10, 20, and 30° at various wind-velocities have been simulated by FireFoam, which is a large eddy simulation (LES) solver of the OpenFOAM platform. The numerical data have been validated using the aerodynamic measurements of a full-scale building model in the absence of fire effects. The results underlined the physical phenomena contributing to the impact of varying wind flow and terrain slope near the fire bed on a built area. The findings indicated that under a constant heat release rate and upstream wind velocity, increasing the upslope terrain angle leads to an increase in the higher temperature areas on the ground near the building. It is also found that raising the inclined terrain slope angle from 0 to 30°, results in an increase in the integrated temperature on the surface of the building. Furthermore, by raising the terrain slope from 0 to 30°, the integrated temperature on the ground for the mentioned cases increases by 16%, 10%, and 13%, respectively.

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The Global Ecosystem Dynamics Investigation LiDAR (GEDI) is a new full waveform (FW) based LiDAR system that presents a new opportunity for the observation of forest structures globally. The backscattered GEDI signals, as all FW systems, are distorted by topographic conditions within their footprint, leading to uncertainties on the measured forest variables. In this study, we explore how well several approaches based on waveform metrics and ancillary digital elevation model (DEM) data perform on the estimation of stand dominant heights (Hdom) and wood volume (V) across different sites of Eucalyptus plantations with varying terrain slopes. In total, five models were assessed on their ability to estimate Hdom and four models for V. Results showed that the models using the GEDI metrics, such as the height at different energy quantiles with terrain data from the shuttle radar topography mission’s (SRTM) digital elevation model (DEM) were still dependent on the topographic slope. For Hdom, an RMSE increase of 14% was observed for data acquired over slopes higher than 20% in comparison to slopes between 10 and 20%. For V, a 74% increase in RMSE was reported between GEDI data acquired over slopes between 0–10% and those acquired over slopes higher than 10%. Next, a model relying on the height at different energy quantiles of the entire waveform (HTn) and the height at different energy quartiles of the bare ground waveform (HGn) was assessed. Two sets of the HGn metrics were generated, the first one was obtained using a simulated waveform representing the echo from a bare ground, while the second one relied on the actual ground return from the waveform by means of Gaussian fitting. Results showed that both the simulated and fitted models provide the most accurate estimates of Hdom and V for all slope ranges. The simulation-based model showed an RMSE that ranged between 1.39 and 1.66 m (between 26.76 and 39.26 m3·ha−1 for V) while the fitting-based method showed an RMSE that ranged between 1.26 and 1.34 m (between 26.78 and 36.29 m3·ha−1 for V). Moreover, the dependency of the GEDI metrics on slopes was greatly reduced using the two sets of metrics. As a conclusion, the effect of slopes on the 25-m GEDI footprints is rather low as the estimation on canopy heights from uncorrected waveforms degraded by a maximum of 1 m for slopes between 20 and 45%. Concerning the wood volume estimation, the effect of slopes was more pronounced, and a degradation on the accuracy (increased RMSE) of a maximum of 20 m3·ha−1 was observed for slopes between 20 and 45%.

Three-dimensional phase unwrapping is one of the key steps of time-series interferometric syn- thetic aperture radar (InSAR) technology. The unwrapping results directly affect the accuracy of time-series InSAR land subsidence monitoring. Aiming at the problem of the whole period unwrapping error caused by phase undersampling in areas with serious land subsidence and large change of terrain slope, a weighted least squares phase unwrapping algorithm based on frequency confidence is proposed, which replaces the weighted least squares phase unwrapping algorithm based on phase gradient in the time-dependent three-di- mensional phase. By improving the accuracy of phase slope change estimation, the accuracy and stability of spatio -temporal three-dimensional phase unwrapping can be improved. The land subsidence results of the typical area in Beijing are obtained by using the improved spatio-temporal three-dimensional phase unwrap- ping method. Compared with the classical spatio - temporal three - dimensional phase unwrapping method, the improved method can obtain higher accuracy of land subsidence monitoring results. Especially for the subsidence funnel region where the slope changes greatly and the decorrelation exists obviously, the subsid- ence monitoring accuracy has improved significantly. [ABSTRACT FROM AUTHOR]

Knowing the variation of the water consumption of a crop or vegetation can help to avoid damages caused by the lack of water, besides allowing a better knowledge of the environment around. Thus, variations in evapotranspiration in sugarcane, planted forest, and native forest were examined as a function of relief variations and terrain exposure in the northeast sector of the State of São Paulo, Brazil (20°43′55.2″S–22°36′28.8″S, 46°37′48.0″W–48°50′16.8″W). These areas, covering a total of 2232 km2, were studied using monthly Landsat 8 satellite data (Path 220 and Row 75) collected over 24 months from April 2013 to March 2015. Thus, this study aimed to use a hybrid Two Source Energy Balance (TSEB), adjusted to convert hourly ET to monthly and annually data, in obtaining ET for two years to areas with sugarcane, planted and native forests and evaluate how this evapotranspiration behaves spatially for some parameters, as altitude, slope, exposure faces of the terrain and biomes, using multivariate analysis. The results identified three evapotranspiration groups: highest evapotranspiration in the highest altitudes and topographic slope; medium evapotranspiration in medium altitudes and slopes; and low evapotranspiration at low altitudes and slopes. The highest rates of evaporation occurred in summer and fall, when temperatures were highest. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Species richness increases with the degree of occupancy of the mine spoil habitat. • Low taxonomic diversity on dump is due to the numerous terricolous Cladonia species. • Nested species composition along the combined, spoil habitat fraction-slope gradient. • Most corticolous and saprophytic species shared with the adjacent agro-pastoral area. • Many oligotrophic, epigeous lichens dispersed probably from proximal source-habitats. Abstract We aimed to detect species distribution patterns at landscape level that have arisen following the colonisation of a mine spoil heap (MSH) by macrolichens. All taxa occurring on various substrates and the degree of occupancy by different vegetation patch types were recorded at a resolution of 50 m × 50 m within a regular square grid of 25 ha, which extended over a 60-year-old abandoned MSH and its adjacent agro-pastoral area. The fraction of MSH was the most important predictor of the lichen composition and richness at grid cell level, followed by the terrain slope and the proportion of heathland. Almost all lichen taxa positively correlated with the MSH fraction were terricolous, fruticose, oligotrophilous, acidophilous species that occurred preferentially on the steep, barren slopes. The few corticolous, nitrophilous species were negatively correlated with the MSH fraction. Except for the corticolous and saprophytic species, the proportion of MSH and the elevation range had each a positive effect on both total and terricolous lichen richness. Conversely, taxonomic distinctness displayed an opposite pattern. Such a contrast was determined by the numerous conspecific (Cladonia) lichens occurring on the steeper MSH slopes, with scarce vegetation. A conspicuous nestedness, but no pattern of species turnover, was detected along the main ecological gradient. This was due to both the corticolous/saprophytic species shared with the adjacent, tailings-free habitats and the terricolous/saxicolous lichens dispersed from proximal source-habitats. The MSH studied can be considered a hotspot for lichen species richness but not for taxonomic diversity. [ABSTRACT FROM AUTHOR]

Certain advantages of using mountainous terrain for the installation of solar plants are well known, such as lower temperature, higher solar irradiance present at high altitudes, and economic aspects related to the lower cost of land. This paper highlights another one: the higher annual solar irradiation incident of single-axis N-S trackers installed on sloping terrain, as compared to horizontal ones. After a theoretical study in which the relevant formulas are derived, numerical simulations are presented. Then we showcase the results of a year-long experiment in which a N-S aligned single-axis tracker prototype was used, at the location of our Department (Gijón, Spain). The experimental results confirm the trends in the formulas and simulations. Finally, theoretical values for the energy gain for different slopes, at locations over the northern hemisphere between latitudes of 6 ° and 60 ° are provided. These gains can reach values up to 13.5%. • N-S oriented solar trackers in sloped terrain receive higher solar irradiation. • Formulas and simulations are included for irradiation in sloped terrains. • Results of a year-long experiment are included for a location in Gijón (Spain). • Experiment confirms the theoretical and numerical ones. Gains can be up to 10%. • Numerical estimations for latitudes between 6° and 60° are provided. [ABSTRACT FROM AUTHOR]

Terrain traficability is one of the key activities of military planning, firefighting and emergency interventions. Terrain traficability is affected by many factors and terrain slope is one of them. Deceleration ratio that represents the influence of slope inclination is dependent on a technical attributes of vehicle. The results of field terrain tests suggest that deceleration ratio established via calculation does not have to correspond with practical experience.

Research Highlights: Technology advances have allowed for a new approach to research the decline of the Korean fir (Abies koreana E.H.Wilson). This study provides insights into the exact causes leading to this decline. Background and Objectives: Various factors could lead to the decline of fir trees around Mt. Halla, Korea, but these have not yet been verified. Here, the Korean fir across Mt. Halla were classified as dead or living and mapped using high-resolution orthorectified aerial images and three-dimensional (3D) stereoplotting. Materials and Methods: Aerial photographs were used to map spatial distribution and analyze the distribution patterns and mortality of the Korean fir. The electronic stereoplotting program (Geo3Di-PRO) enabled the creation of 3D images from aerial photographs. General, altitudinal, and topographical distribution was assessed. Results: Their accumulated percent mortality rate (APMR) showed positive correlations with altitude and tree density, a negative correlation with terrain slope, and no consistent correlation with solar radiation. The results indicate that increases in the density of Korean firs are related to decreased growth in areas at high altitude, on gentle slopes, and with high solar radiation. Consistent positive correlations between density and APMR indicate that fir mortality can be attributed to environmental deterioration and the establishment of unfavorable growth conditions. Areas with high APMR and density had gentle slopes, thus high soil moisture, or relatively high annual precipitation owing to high altitude. Conclusion: Fir mortality on Mt. Halla can be attributed to long-term persistently high rainfall and subsequent excess soil moisture.

Comparison analysis was performed for the characteristics of cloud-to-ground (CG) lightning and topography in low latitude plateau of China and showed that CG lightning activity was characterized Gaussian distribution along the variation of elevation centered at approximately 2000 m above sea level and decreased on both sides; it was also linearly inversely correlated with variations in terrain slope. CG lightning activity was showed a typical positive dipole distribution of electric charges in the thunderstorm clouds. The average current intensity of negative CG lightning located in the lower layers was obviously weaker than that of the positive CG lightning located in the upper layers, and decreased initially and subsequently increased as the elevation increased, whereas the positive CG lightning had no significant variation. The CG lightning current intensity increased linearly with terrain slope, and the variation slope of positive CG lightning was smaller than that of negative CG lightning, variation of current intensity with latitude was inversely correlated with the variation of CG lightning densities. The CG lightning activity and variation of current intensity had the same characteristics in specific regions and in zonal and meridional cross-sections, but it was significantly affected by the topography in the low/high regions where elevation was <600 />3500 m. [ABSTRACT FROM AUTHOR]

Optimal vehicle off-road path planning problem must consider surface physical properties of terrain and soil. In this paper, we firstly analyse the comprehensive influence of terrain slope and soil strength to vehicle’s off-road trafficability. Given off-road area, the GO or NO-GO tabu table of terrain gird is determined by slope angle and soil remolding cone index (RCI). By applying tabu table and grid weight table, the influence of terrain slope and soil RCI are coordinated to reduce the search scope of algorithm and improve search efficiency. Simulation results based on tracked vehicle M1A1 in off-road environment show that, improved ant colony path planning algorithm not only considers the influence of actual terrain and soil, but also improves computation efficiency. The time cost of optimal routing computation is much lower which is essential for real time off-road path planning scenarios. [ABSTRACT FROM AUTHOR]

Models of geomorphometric parameters and drainage networks are widely used in many scientific and civilian branches and activities. They are created using the Earth's land surface data, which are today mostly represented by digital elevation models (DEMs). The main objective of this study is to create models of slope, aspect, and drainage networks for the first time for the entire continental part of the Republic of Croatia, using the most detailed DEMs. In this paper, developed models are described, compared, and analysed, giving insights into morphological characteristics and structures of topographic surface. The quality of the derived models has been validated using existing independent data. Furthermore, because models were derived using various global DEMs, the differences between output models have been addressed and studied. Drainage network models were further analysed depending on several available computation algorithms (single and multiple flow direction) and threshold values. The analysis of the sensitivity and influence of input parameters and models on output models has been assessed in order to create reliable drainage network models for the future for other local or regional areas. [ABSTRACT FROM AUTHOR]

The accurate estimation of terrain slope is very important for accurately monitoring the elevation and mass changes of glacier using laser altimeter. In this paper, a novel physical model was proposed for accurately estimating within-footprint terrain slope. The new proposed model was built based on overlapping footprints of the geoscience laser altimeter system (GLAS) data, namely, using altitude angle, footprint size, shape, orientation, terrain aspect, and ground extent. Ground extent estimation models were established on the basis of linear regression analyses between: 1) GLAS-derived waveform extent and airborne topographic mapper (ATM)-derived ground extent and 2) GLAS-derived waveform width and ATM-derived ground extent, respectively. In addition, the terrain slopes estimated from the overlapping footprints were validated by ATM data and compared with the slopes calculated from surface elevations, i.e., from ASTER global digital elevation model (DEM) (GDEM) and GLAS elevation. Results showed that the accuracy of waveform width-predicted ground extents (R² = 0.868, RMSE = 0.686 m, n = 20, and p-value < 0.0001) is higher than that of waveform extent-predicted ground extents (R² = 0.776, RMSE = 0.824 m, n = 20, and p-value < 0.0001), which indicated that waveform width is more suitable for estimating ground extent. Slopes estimated from the new proposed model have a strong consistency with those calculated from ATM data (Corrcoef = 0.786, bias = 0.654°, SD = 1.368°, and RMSE = 1.452°). Additionally, results also indicated that the new proposed model performs much better than the methods based on ASTER GDEM and the GLAS surface elevation in estimating within-footprint terrain slope due to higher correlation, lower bias, standard deviation, and RMSE. [ABSTRACT FROM AUTHOR]

This paper investigates the potential of the time-frequency optimization on the basis of the sublook decomposition for forest height estimation. The optimization is deemed to be capable of extracting a relatively accurate volume contribution when P-band polarimetric interferometric synthetic aperture radar (Pol-InSAR) systems are adopted to observe forest-covered areas. The highest and the lowest phase centers acquired by the time-frequency optimization modify the conventional three-stage inversion process. This paper presents, for the first time, a performance assessment of the time-frequency optimization on P-band Pol-InSAR data over boreal forests. Simultaneously, to alleviate the model inversion errors caused by topographic fluctuations, forest height is estimated based on the sloped Random Volume over Ground (S-RVoG) model in which the incidence angle is corrected with the terrain slope. The E-SAR P-band Pol-InSAR data acquired during the BIOSAR 2008 campaign in Northern Sweden is utilized to evaluate the performance of the proposed method. From the results of the forest height estimation preprocessed with time-frequency optimization, the root mean square error (RMSE) of Random Volume over Ground (RVoG) and S-RVoG model on negative slope are 5.09 m and 4.71 m, respectively. It is concluded that the time-frequency processing and negative terrain slope compensation improve the inversion performance by 41 . 49 % and 11 . 96 % , respectively.

This paper presents the results of an analysis of the position and density of a secondary road network in the group-selection management system. The research was conducted in the economic unit Prosara in the north west of the Republic of Srpska. The network of skid roads in the analyzed sections was recorded using the GPS devices Garmin GPS 60 and Garmin Map 62st, and the analysis software package used was ESRI ArcInfo 10.1. Adhering to the general guidelines, the slope of skid roads was analyzed within six predefined intervals: 0-12 %, 12-16 %, 16-20 %, 20-30 %, 30-40 % and over 40%. Relative openness with a secondary road network was determined for a maximum distance between the skid roads of 130m and it ranged from 82.62 % to 96.37 %. Such openness was classified as very good and excellent. Together with all factors related to stand and terrain characteristics, it appears that in all the compartments, the density of the secondary network of skid roads is adequate for the application of a skidder with a winch, without extending above the maximum length of the winch rope. Out of the total length of analyzed skid roads, 24% is within an appropriate slope interval for a planned conversion to truck roads, whereas 37 % is the maximum slope from the ecological point of view. The average terrain slope for the whole analyzed area is 26.4%. Such moderately sloping terrain is suitable for the construction of skid roads with low investment and small environmental impact. Due to their specific configuration, the main skid roads were designed along the ridge, while the secondary and tertiary skid roads most often separated from them at the maximum slope, forming an irregular fish bone shape.