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Forest road maps are a fundamental source of information for the sustainable management, protection, and public utilization of forests. However, the precision of these maps is crucial to their use. In this context, we assessed and compared the elevation accuracy of terrain on three forest road surfaces (i.e., asphalt, concrete, and stone), which were derived based on data from three remote sensing technologies (i.e., aerial imaging, airborne laser scanning, and mobile laser scanning) using five geospatial techniques (i.e., inverse distance; natural neighbor; and conversion by average, maximal, and minimal elevation value). Specifically, the elevation accuracy was assessed based on 700 points at which elevation was measured in the field, and these elevations were extracted from fifteen derived forest road maps with a resolution of 0.5 m. The highest precision was found on asphalt roads derived from mobile laser scanning data (RMSE from ±0.01 m to ±0.04 m) and airborne laser scanning data (RMSE from ±0.03 m to ±0.04 m). On the other hand, the lowest precision was found on all roads derived from aerial imaging data (RMSE from ±0.11 m to ±0.23 m). Furthermore, we found significant differences in elevation between the measured and derived terrains. However, the differences in elevation between specific techniques, such as inverse distance, natural neighbor, and conversion by average, were mostly random. Moreover, we found that airborne and mobile laser scanning technologies provided terrain on concrete and stone roads with random elevation differences. In these cases, it is possible to replace a specific technique or technology with one that is similar without significantly decreasing the elevation accuracy (α = 0.05). [ABSTRACT FROM AUTHOR]

Copyright of Engineer Military Bulletin / Muszaki Katonai Közlöny is the property of National University of Public Service and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The real-time rendering of large-scale terrain scenes has been a challenge and is a popular research topic in the fields of 3D games and virtual reality. To fully utilize GPU features, this paper proposes a real-time rendering algorithm for large-scale regular grid terrain based on GPU Tessellation. The CPU processes a coarse-grained quadtree to generate terrain patches and then passes the patches to the GPU after view culling. Then, the GPU refines the terrain by using GPU Tessellation and displacement mapping. The most important advantage of our method is that during the tessellation stage, a new rule that the distance, screen space projection error and variance of the height, as the standard of terrain roughness, is designed. During the tessellation stage, the distance, screen space projection error and variance of the height, as the standard of terrain roughness, are considered. The experimental results show that our algorithm can greatly reduce the CPU processing time and main memory space requirement, and fully utilize the new features of the GPU; In conclusion, the proposed approach can render large-scale terrain with high-precision in real-time.

The mountain model developed by Fookes et al. (Eng Geol 21:1–152, 1985) comprised four terrain zones applicable to the Himalayan foothills in which the 50 km-long road from Dharan to Dhankuta was designed and constructed between 1974 and 1982. Forty years on, performance assessment of the completed road shows that the model has proven successful in allowing landslide and fluvial hazards and problematic ground conditions to be anticipated and hence accommodated in route selection and engineering design. Persistent slope failure and resultant road damage have occurred at two locations only, both in the vicinity of major thrust faults, and both in response to exceptional rainfall and earthquakes. Nevertheless, a total of 1.5 km of the road length in valley floor terrain has been repeatedly destroyed by river scour or blocked by debris at tributary fan crossings. The potential for these fluvial hazards was recognised in the mountain model, but considerations of cost and construction expediency prevailed over engineering geological advice. Despite these outcomes, less than 3% of the alignment suffers from recurrent damage, and it is concluded that the road has performed well in comparison to some others in Nepal. The use of models such as that developed by Fookes et al. (1985) provides a valuable means for assessing the potential geohazards and ground engineering problems posed by different route and design options. [ABSTRACT FROM AUTHOR]

We evaluated a novel tool that predicts possible maternity den habitat of the polar bear (Ursus maritimus) based on a physical snow transport model, a digital terrain model and weather data. We observed and compared den locations in three important denning areas in east Svalbard (Kongsøya, n = 288; Svenskøya, n = 86; Hopen, n = 115) with modelled snowdrift distributions for 24 years. Accounting for a likely position uncertainty of 100 m, 69% of all dens were located within year-specific modelled snowdrifts. These covered on average 1.8%, 2.1% and 24.7% of the three study islands, respectively. Our snowdrift model accurately predicted maternity den positions (R2 = 0.42, area under the receiving operating characteristic curve [AUC] = 0.85). A model based on slope and altitude, also predicted den positions reasonably well (R2 = 0.35, AUC = 0.88). Habitat maps identifying both current and future areas for maternity denning will become important in managing the Barents Sea population as well as other Arctic populations where changes in sea-ice conditions alter the accessibility to traditional denning areas.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The performance of 2D LiDAR SLAM in simulated orchards is evaluated. • Three typical algorithms Hector, GMapping, and Cartographer are investigated. • A scalable terrain simulation model is built with adjustable roughness. • Evaluation metrics are localization/mapping errors and CPU/memory usage. • Adaptability to terrain roughness, LiDAR model, and orchard size is evaluated. Accurate localization is a prerequisite for developing autonomous mobile orchard robots. Simultaneous localization and mapping (SLAM) is an efficient technique for localizing robots in global navigation satellite system (GNSS)-denied scenarios. Light detection and ranging (LiDAR) is one of the most crucial sensors used for environment perception. Two-dimensional (2D) LiDAR SLAM has been successfully applied in various indoor scenes to construct flat maps and estimate robot trajectories. In this paper, the performances of three representative 2D LiDAR SLAM algorithms, namely, Hector, GMapping, and Cartographer, in semi-structured orchard environments simulated in Gazebo are analysed. A hierarchical terrain modelling method is proposed to generate scalable orchard terrain with adjustable roughness. The adaptability of the three algorithms to terrain roughness, LiDAR, and orchard size is evaluated in terms of the localization error, mapping error, CPU usage, and memory usage. The experimental results show that Cartographer has the highest location and mapping accuracy, followed by GMapping and Hector. However, Hector requires the least computational resources, followed by Cartographer and GMapping. In a 50 m × 50 m orchard with an elevation difference of 15 cm, Cartographer achieved a localization error of 8.14 cm and a mapping error of 8.43 cm at a 4 cm map resolution. In addition, Hector has the highest requirements for the maximum range and field-of-view (FOV) of LiDAR, and GMapping is most susceptible to severe uneven terrain conditions and has the worst scalability for large-scale orchards. [ABSTRACT FROM AUTHOR]

The real-time rendering of large-scale terrain scenes has been a challenge and is a popular research topic in the fields of 3D games and virtual reality. To fully utilize GPU features, this paper proposes a real-time rendering algorithm for large-scale regular grid terrain based on GPU Tessellation. The CPU processes a coarse-grained quadtree to generate terrain patches and then passes the patches to the GPU after view culling. Then, the GPU refines the terrain by using GPU Tessellation and displacement mapping. The most important advantage of our method is that during the tessellation stage, a new rule that the distance, screen space projection error and variance of the height, as the standard of terrain roughness, is designed. During the tessellation stage, the distance, screen space projection error and variance of the height, as the standard of terrain roughness, are considered. The experimental results show that our algorithm can greatly reduce the CPU processing time and main memory space requirement, and fully utilize the new features of the GPU; In conclusion, the proposed approach can render large-scale terrain with high-precision in real-time. [ABSTRACT FROM AUTHOR]

The students of the Defense University Center at the Spanish Naval Academy (Marín, northwest of Spain) attend both the military studies and mechanical engineering degrees. These students are the future officers of the Spanish Navy. Among them, the Marine Corp students attend subjects focused on topography, Geographic Information Systems (GIS) and an amphibious landing. In this framework, this paper presents an example of an application of the use of physical models for a better understanding of the terrain, as well as for landscape design or military planning. Through the use of different GIS and Computer-Aided Design software, the students have to demonstrate their capabilities to create and produce three-dimensional (3D) printed models. This work shows how the use of printed scale models of the terrain offers visualization advantages and more understanding to students when compared with virtual models or traditional maps. Additionally, a methodological approach is presented aiming to produce 3D-printed models using open data sources and free license software. From a point cloud of data, this software allowed creating and editing the virtual model (scales, vertical exaggeration, smooth, etc.), as well as to merge different point clouds. The methodology was applied to the Island of Tambo (Galicia, Spain). Using Light Detection and Ranging data, several printed scale models were elaborated on, including the Digital Terrain Model and Digital Elevation Model. Additionally, a bathymetric model was created, aiming to assist in the design of an amphibious operation. [ABSTRACT FROM AUTHOR]

We evaluated a novel tool that predicts possible maternity den habitat of the polar bear (Ursus maritimus) based on a physical snow transport model, a digital terrain model and weather data. We observed and compared den locations in three important denning areas in east Svalbard (Kongsøya, n = 288; Svenskøya, n = 86; Hopen, n = 115) with modelled snowdrift distributions for 24 years. Accounting for a likely position uncertainty of 100 m, 69% of all dens were located within year-specific modelled snowdrifts. These covered on average 1.8%, 2.1% and 24.7% of the three study islands, respectively. Our snowdrift model accurately predicted maternity den positions (R2 = 0.42, area under the receiving operating characteristic curve [AUC] = 0.85). A model based on slope and altitude, also predicted den positions reasonably well (R² = 0.35, AUC = 0.88). Habitat maps identifying both current and future areas for maternity denning will become important in managing the Barents Sea population as well as other Arctic populations where changes in sea-ice conditions alter the accessibility to traditional denning areas. [ABSTRACT FROM AUTHOR]

The quality of the information about the wind field characteristics is crucial for accurately predicting the structural response of a long-span bridge subjected to dynamic wind loads. In this paper, in situ mast measurements and terrain model wind tunnel tests are compared with full-scale measurements of the wind field along the Hardanger Bridge girder. The aim is to investigate the performance of mast measurements and wind tunnel terrain model tests in predicting the wind field characteristics for long-span bridges in complex terrains. Wind field spatial variations and statistical distributions for the mean wind velocity and turbulence intensity are investigated. Extreme value statistics have been applied to compare the mean wind velocity recordings from two different measurement periods. Results showing terrain-induced effects on the wind directions, turbulence intensities and mean wind velocities are presented. Simultaneous spanwise wind profiles for the mean wind velocity and along-wind turbulence intensity are compared between the terrain model wind tunnel tests and the full-scale measurements, and large nonuniformities are identified. The extreme profiles of the turbulence intensities vary as much as 100% along the span, and the mean wind velocity profiles vary up to 50% along the span. [ABSTRACT FROM AUTHOR]

3D data fusion is a research hotspot in the field of computer vision and fine mapping, and plays an important role in fine measurement, risk monitoring, data display and other processes. At present, the research of 3D data fusion in the field of Surveying and mapping focuses on the 3D model fusion of terrain and ground objects. This paper summarizes the basic methods of 3D data fusion of terrain and ground objects in recent years, and classified the data structure and the establishment method of 3D model, and some of the most widely used fusion methods are analysed and commented. [ABSTRACT FROM AUTHOR]

In the geographic information field, triangular mesh modes are often used to describe terrain, where the normal vector to the surface at the node of a triangular mesh plays an important role in reconstruction and display. However, the normal vectors on the nodes of triangular meshes cannot be given directly, but instead must be computed using known data. Currently, the most common method of computing the normal vector at the nodes on a triangular mesh is to sum the normal vectors of the adjacent triangular facets using various weighting factors. For complex terrain surfaces, such a method is not very effective, and in some cases is not as good as classical weighted average algorithms. By studying interpolation based on edge-direction, combined with a terrain triangular mesh, we propose using a GPU-Parallel normal vector interpolation meth od based on the edge-direction for a terrain triangular mesh. Since terrain data is usually large, traditional serial algorithms are difficult to use while still meeting real-time requirements. In this paper, we use CUDA optimization strategies to make full use of the GPU (NVIDIA TESLA K80) for effectively solving this problem. The experimental results show that compared to traditional weighted average algorithms, the accuracy of the normal vector to the surface at the node increases significantly, and compared to serial algorithms only on CPU, speeds are increased by 646.4 times with the I/O transfer time being taken into account, meeting the real-time requirements. [ABSTRACT FROM AUTHOR]

SUMMARY Analysis of lightning electromagnetic field using the finite-difference time-domain (FDTD) method has been studies in recent year. However, large-scale analysis on real environment has not been considered, because the FDTD method requires huge computational cost on large-scale analysis. We proposed a three-dimensional moving window FDTD (MW-FDTD) with parallel computation and applied to large-scale analysis of lightning electromagnetic field with a real numerical terrain model. In this paper, we have studied about large-scale analysis of lightning electromagnetic field with real urban models considering many buildings using our MW-FDTD with parallel computation. We have shown effects of observed electromagnetic field on urban model. [ABSTRACT FROM AUTHOR]

Topografski podatki, kot pomemben del Nacionalne prostorske podatkovne infrastrukture, so bili v letih po osamosvojitvi Slovenije deležni velike pozornosti, postali so splošno dostopni, bili so dopolnjeni in medsebojno usklajeni. V zadnjem desetletju pa se je vlaganje v topografske podatke v Sloveniji zelo omejilo, zato danes nikakor več ne moremo biti zadovoljni z njihovim stanjem. V prispevku pregledno predstavljamo stanje topografskih podatkov v Sloveniji, analiziramo njihovo kakovost in ustreznost za potencialne in dejanske uporabnike. Posvetimo se izvornim posnetkom stanja, kot je sistemsko ciklično aerosnemanje (CAS), in iz njega izvedenemu proizvodu, ortofotu. Kakovost ortofota je precej odvisna od kakovosti modela reliefa. Topografski podatki so vodeni posamično v sklopu posameznih vsebinskih baz (REZI, ZK GJI, grafični del katastra stavb) ter združeno v topografskih bazah in kartah različnih ravni podrobnosti (DTK 5, DTK 25, DTK 50, sistem DPK). Analizirano stanje primerjamo s stanjem v nekaterih sosednjih ali primerljivih državah ; Topographic data, an important part of the National Spatial Data Infrastructure, have been given serious attention since Slovenia’s independence. It has become publicly available, updated and harmonised. Financing of topographic data in Slovenia has significantly decreased over the previous decade. As a result, the present status is far from acceptable or expected. The current status of the topographic data, as well as its quality and usability for potential users is discussed in this article. The overview starts with basic source data, aerial surveys, photographs and orthophotos. The quality of orthophotos largely depends on the DTM quality. Topographic data is nowadays organised in thematic datasets (geographical names, building cadastre, etc.) or joined in datasets of different levels of accuracy and details. The status in Slovenia is compared to those in some neighbouring and other comparable countries.

Substantial progress has been achieved over the last four decades to better understand a deep structure in the Himalayas and Tibet. Nevertheless, the remoteness of this part of the world still considerably limits the use of seismic data. A possible way to overcome this practical restriction partially is to use products from the Earth’s satellite observation systems. Global topographic data are provided by the Shuttle Radar Topography Mission (SRTM). Global gravitational models have been derived from observables delivered by the gravity-dedicated satellite missions, such as the Gravity Recovery and Climate Experiment (GRACE) and the Gravity field and steady-state Ocean Circulation Explorer (GOCE). Optimally, the topographic and gravity data should be combined with available results from tomographic surveys to interpret the lithospheric structure, including also a Moho relief. In this study, we use seismic, gravity, and topographic data to estimate the Moho depth under orogenic structures of the Himalayas and Tibet. The combined Moho model is computed based on solving the Vening Meinesz⁻Moritz (VMM) inverse problem of isostasy, while incorporating seismic data to constrain the gravimetric solution. The result of the combined gravimetric-seismic data analysis exhibits an anticipated more detailed structure of the Moho geometry when compared to the solution obtained merely from seismic data. This is especially evident over regions with sparse seismic data coverage. The newly-determined combined Moho model of Tibet shows a typical contrast between a thick crustal structure of orogenic formations compared to a thinner crust of continental basins. The Moho depth under most of the Himalayas and the Tibetan Plateau is typically within 60⁻70 km. The maximum Moho deepening of ~76 km occurs to the south of the Bangong-Nujiang suture under the Lhasa terrane. Local maxima of the Moho depth to ~74 km are also found beneath Taksha at the Karakoram fault. This Moho pattern generally agrees with the findings from existing gravimetric and seismic studies, but some inconsistencies are also identified and discussed in this study.

We demonstrate the efficacy of using close-range photogrammetry from a consumer grade camera as a tool in generating high-resolution, three-dimensional coloured point clouds for detailed analysis or monitoring of wheel ruts. Ground-based timber harvesting results in vehicle traffic on 12-70 per cent of the site, depending on the system used, with a variable probability of causing detrimental soil disturbance depending on climatic, hydrological and soil conditions at the time of harvest. Applying the technique described in this article can reduce the workload associated with the conventional manual measurement of wheel ruts, while providing a greatly enhanced source of information that can be used in analysing both physical and biological impact, or stored in a repository for later operation management or monitoring. Approaches for deriving and quantifying properties such as rut depths and soil displacement volumes are also presented. In evaluating the potential for widespread adoption of the method among forest or environmental managers, the study also presents the work-flow and provides a comparison of the ease of use and quality of the results obtained from one commercial and two open source image processing software packages. Results from a case study showed no significant difference between packages on point cloud quality in terms of model distortion. Comparison of photogrammetric profiles against profiles measured manually resulted in root mean square errors of between 2.07 and 3.84 cm for five selected road profiles. Maximal wheel rut depth for three different models were 1.15, 0.99 and 1.01 m, and estimated rut volumes were 9.84, 9.10 and 9.09 m³, respectively, for 22.5 m long sections. [ABSTRACT FROM AUTHOR]

The capabilities of unmanned airborne systems (UAS) have become diverse with the recent development of lightweight remote sensing instruments. In this paper, we demonstrate our custom integration of the state-of-the-art technologies within an unmanned aerial platform capable of high-resolution and high-accuracy laser scanning, hyperspectral imaging, and photographic imaging. The technological solution comprises the latest development of a completely autonomous, unmanned helicopter by Aeroscout, the Scout B1-100 UAV helicopter. The helicopter is powered by a gasoline two-stroke engine and it allows for integrating 18 kg of a customized payload unit. The whole system is modular providing flexibility of payload options, which comprises the main advantage of the UAS. The UAS integrates two kinds of payloads which can be altered. Both payloads integrate a GPS/IMU with a dual GPS antenna configuration provided by OXTS for accurate navigation and position measurements during the data acquisition. The first payload comprises a VUX-1 laser scanner by RIEGL and a Sony A6000 E-Mount photo camera. The second payload for hyperspectral scanning integrates a push-broom imager AISA KESTREL 10 by SPECIM. The UAS was designed for research of various aspects of landscape dynamics (landslides, erosion, flooding, or phenology) in high spectral and spatial resolution. [ABSTRACT FROM AUTHOR]

Tools for accurately predicting environmental risks, such as the location and spatial extent of potential inundation, are not widely available. A dependence on calibration and a lack of available flood data have prevented the widespread application of existing hydrodynamic methods for predicting the extent of inundation. We use the height above the nearest drainage (HAND) terrain model to develop a simple static approach for mapping the potential extent of inundation that does not depend on flood observations and extends beyond methods for mapping low-lying areas. While relying on the contour concept, the method utilizes drainage-normalized topography and flowpaths to delineate the relative vertical distances (drop) to the nearest river. The HAND-delineated relative drop is an effective distributed predictor of flood potential, which is directly related to the river stage height. We validated the new HAND contour approach using a flood event in Southern Brazil for which high-resolution maps were available. The results indicated that the flood hazard-mapping method accurately predicted the inundation extent of the channel carrying the flood wave and the channels influenced by flooding. For channels positioned outside of the flood-wave area, the method overestimated the actual flood extent. As an original static assessment of floodwaters across the landscape, the HAND contour method could be used to map flood hazards in areas with poor information and could promote the development of new methods for predicting hydrological hazards. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The aim of this research was to develop an operational method of characterization of «terroirs» in response to the request from wine professionals. A study based on both a survey of vine growers and a characterization of the natural factors of «terroir» (geological, pedological and mesoclimatic components) using the concept of Basic Terroir Unit (B.T.U) was made in 18 communes of the Anjou region. The natural factors of “terroir” were characterized by (1) a geological component (stage and nature of the parent rock) and (2) an agro-pedological component studied according to a field model allowing to distinguish three kinds of soil environments named : Rock, Alteration and Altérite. Each of them represent a functioning unit in wich an homogenous response in terms of vine behaviour can be expected. The approach based on the survey of vine growers was developed in order to replace the network of experimental plots of land formerly used to integrate the plant behaviour in its environment. These networks required considerable investment in time and money. Our study showed that vine growers perceived correctly the behaviour of the vine through different variables relative to the soil, the climate and the plant. They distinguished particularly well between two of the environments (Rock and Alterite) generated by the model. There was good agreement between the results obtained with the two approaches (survey and characterization of natural factors of «terroirs»).

In the field of geographic information, fast surface modelling techniques are important. Usually, mesh model is used to describe the terrain. However, the large data of mesh model are a bottleneck of real-time rendering. Compared with the CPU, GPU has more execution units and memory units, which greatly improves its computing capacity and memory bandwidth. Meanwhile, in the field of image rendering, OpenGL has always played an important role. Since CUDA (compute unified device architecture) and OpenGL both run on GPU and share data through common memory, this paper gives a three-dimensional terrain real-time rendering method based on CUDA–OpenGL interoperability. First, we use CUDA C kernel function to calculate the vertex coordinates and normal vectors, then we pass the data to OpenGL buffer, and render it. In this paper, we use share memory and register, overlap strategy, the expansion of concurrency and the reasonable block size. The experimental results show that this algorithm can improve the computing speed greatly, with the speedup to 212.3x, meeting the needs of real-time rendering. [ABSTRACT FROM PUBLISHER]

Copyright of Österreichische Wasser- und Abfallwirtschaft is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Geographical information system (GIS) data in digital elevation model (DEM) format contains surface data of terrain on the Earth. This surface data needs to be converted into a 3D faceted file before uploading to an additive manufacturing (AM) machine. Commercially available software packages perform this task indirectly by translating and modifying data through different file formats. This paper discusses a methodology to convert the United States Geological Survey (USGS) 7.5-minute and 1-degree DEM file formats directly to 3D stereolithography (STL) ASCII format. A software program in C is developed to create a base and walls around the surface data to make a 3D STL part of the terrain. The STL file was uploaded to an AM machine (EOSP395) to fabricate a physical scale model of the terrain. This work not only removes intermediate steps and the associated data loss but can generate an STL part in relatively less time. [ABSTRACT FROM AUTHOR]

Seismic data are primarily used in studies of the Earth’s inner structure. Since large parts of the world are not yet sufficiently covered by seismic surveys, products from the Earth’s satellite observation systems have more often been used for this purpose in recent years. In this study we use the gravity-gradient data derived from the Gravity field and steady-state Ocean Circulation Explorer (GOCE), the elevation data from the Shuttle Radar Topography Mission (SRTM) and other global datasets to determine the Moho density contrast at the study area which comprises most of the Eurasian plate (including parts of surrounding continental and oceanic tectonic plates). A regional Moho recovery is realized by solving the Vening Meinesz-Moritz’s (VMM) inverse problem of isostasy and a seismic crustal model is applied to constrain the gravimetric solution. Our results reveal that the Moho density contrast reaches minima along the mid-oceanic rift zones and maxima under the continental crust. This spatial pattern closely agrees with that seen in the CRUST1.0 seismic crustal model as well as in the KTH1.0 gravimetric-seismic Moho model. However, these results differ considerably from some previously published gravimetric studies. In particular, we demonstrate that there is no significant spatial correlation between the Moho density contrast and Moho deepening under major orogens of Himalaya and Tibet. In fact, the Moho density contrast under most of the continental crustal structure is typically much more uniform.

Bathymetry data from multibeam echosounders and other acoustic sources are now widely available in the form of digital terrain models, which are conveniently displayed as raster grids in desktop geographic information systems. Calculation of terrain variables such as slope is a simple push-button operation in most geographic information systems; however, as we demonstrate here, there can be a great variation in the slope values obtained due to computation algorithms and resolution or analysis scale. This article also demonstrates how Monte Carlo simulation can be used to visualise uncertainty in the underlying bathymetry dataset and also how this uncertainty impacts on slope calculations. [ABSTRACT FROM AUTHOR]

Skid trails constructed for timber extraction in steep terrain constitute a serious environmental concern if not well planned, executed and ameliorated. Carrying out post-harvest surveys in monitoring constructed trails in such terrain is an onerous task for forest administrators, as hundreds of meters need to be surveyed per site, and the quantification of parameters and volumes is largely based on assumptions of trail symmetry and terrain uniformity. In this study, aerial imagery captured from a multi-rotor Unmanned Aerial Vehicle was used in generating a detailed post-harvest terrain model which included all skid trails. This was then compared with an Airborne Laser Scanning derived pre-harvest terrain model and the dimensions, slopes and cut-and-fill volumes associated with the skid trails were determined. The overall skid trail length was 954 m, or 381 m·ha-1 with segments varying from 40-60 m, inclinations from 3.9% to 9.6%, and cut volumes, from 1.7 to 3.7 m3 per running meter. The methods used in this work can be used in rapidly assessing the extent of disturbance and erosion risk on a wide range of sites. The multi-rotor Unmanned Aerial Vehicle (UAV) was found to be highly suited to the task, given the relatively small size of harvested stands, their shape and their location in the mountainous terrain. [ABSTRACT FROM AUTHOR]

Cartographic products which characterise the relief of Lithuania and have been created during the last century and nowadays are described in this article. The article presents interpretations of the relief of Lithuania by specialists such as foresters, road engineers, geographers, topographers, hydrographers, land owners and geoinformatics. It also analyses the development of the relief of Lithuania via presentation of its qualitative and technological characteristics. Article in Lithuanian Lietuvos reljefas kartografiniuose dokumentuose Santrauka. Pateikta skirtingose Lietuvos žinybose dirbusių specialistų – miškininkų, kelininkų, geografų, topografų, hidrografų, žemėtvarkininkų ir geoinformatikų įvairaus laikotarpio Lietuvos reljefo interpretacijos. Aptariami svarbiausieji Lietuvos reljefą apibūdinantys, pastarojo šimtmečio kartografiniai produktai. Analizuojama Lietuvos reljefo vaizdavimo raida, pateikiama jos kokybinės ir technologinės charakteristikos. Šiek tiek pateikiama informacijos apie kartografinių produktų autorius. Raktažodžiai: topografiniai žemėlapiai, reljefo modelis, izohipsės, morfografinis žemėlapis, geoinformacinė duomenų bazė.

To study the appropriate boundary transition section shape of terrain model for mountains-gorge bridge site, a kind of transition section curves was derived based on the theory of flow around cylinder with ideal fluid. According to the different shapes of the curve transition section with equivalent slope of 0.58 and the ramp transition section with included angle of 30°, an ideal two-dimensional platform terrain was used as the analysis model to comparatively analyze the flow separation behavior and the distribution characteristics of average wind field after airflow flowed along the two transition sections by CFD commercial software FLUENT. Furthermore, the total flow transition lengths of different curve transition section shapes were also compared. The results show that when airflow flows along the curve transition section with equivalent slope of 0.58, the distribution characteristics of wind velocity field after airflow flowed along it are much closer to the distribution characteristics of reference wind velocity field than those when airflow flows along the ramp transition section with included angle of 30°, and its total flow transition length is also the relative shortest. The research conclusions could provide some references for the complex terrain model studies on wind characteristics over the mountains-gorge bridge site by wind tunnel test and CFD methods. [ABSTRACT FROM AUTHOR]