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NASA’s new Earth-Observing satellite namely ICESat-2 estimates the elevation of ice sheets, glaciers, sea ice, land surface, and canopy with the help of photon counting ATLAS sensor on-board. Higher-level data products like ATL08 uses an iterative filtering approach of the signal photons for capturing canopy height and terrain height. This article provides results from the evaluation of best-fit elevation on land from ICESat-2 ATL08 data product with DGPS surveyed points. 40 points were surveyed for elevation in the arid region with different topographies of varied surface cover. Mean bias error computed from the best-fit elevation from ICESat-2 ATL08 data product and corresponding DGPS surveyed points is near close to zero for the segments created from strong beams. The conformity between these two sets of elevation values is better than 12 cm (RMSE) if we use the segments from strong beam for the topographic variations ranging from flat to almost flat type.

In this paper we present a virtual reality application, where multiple users can observe and interact with a portion of geo-referenced terrain where a real wildfire took place. The application presents a layout with two maps, one is a three-dimensional view with terrain elevation and the other is a conventional two-dimensional view. The VR users can control different layers (roads, waterways, etc), control the wildfire’s playback, command vehicles to change positions and paint the terrain conveying information to one-another. This work explores how users interact with map visualizations and plan for a crisis management scenario within a virtual environment.

Inselbergs’ spatial distribution is the primary focus of this study carried out in Igbajo District of Western Nigeria. Additionally, a common hypothesis that spatial distribution of inselbergs is informed by the differing modes of evolution of the landforms was also examined. Inselbergs are defined as points on the topographic sheet and satellite terrain elevation data and are thereafter subjected to point pattern analysis. Two point pattern analyses: Poisson Probability Distribution (PPD) and Nearest Neighbour Analysis (NNA) are employed to determine the pattern of inselberg distribution over space. Additional analysis focused on the relationship between regional river drainage and inselbergs’ spatial distribution. Findings from the study confirmed that inselberg form a clustered distribution. The PPD results suggest that the observed distribution of inselbergs has a statistically significant difference from the expected pattern generated by the random process (c2 test statistic = 49.82 > =12.59 (α= 0.05) and 16.81 (α= 0.01). Similarly, the NNA with a R < 1 (Nearest Neighbour Ratio, R = 0.92) and p-value = -2.52, also indicated a clustered distribution. Analysis of river drainage pattern similarly revealed a cluster of high rising landforms situated in the centre of the regional watershed. It is concluded that inselberg distribution in the study area is clustered although the observed pattern does not necessarily validate or invalidate the alternative evolutionary theories.

Preview elevation values are used as inputs to suspensions to improve a vehicle's ride. In a previous study, we obtained preview terrain elevation information in post-processing. In this paper, we contributed a method to reconstruct the terrain elevation map in real-time to extract preview elevation information according to the predicted trajectory. We use interdisciplinary knowledge to solve an engineering problem in the field of mechanical engineering, and the innovation of this manuscript belongs to Engineering Application Innovation. First, in the process of data collection, the terrain elevation map is updated with LIDAR measurements. A Kalman filter is used to update the elevation map. Second, as the vehicle moves, the uncertainty in the vehicle's motion is estimated, and the error variance that propagates to the terrain elevation map is computed. Third, the vehicle trajectory is predicted based on a vehicle kinematics model. According to the predicted trajectory, the elevation information is extracted from the terrain elevation map in advance. The proposed method has been extensively evaluated with the simulations in Gazebo and outdoor environments, and the results demonstrate that the algorithm is effective, with a maximum error of 2.58 cm for the estimated elevation value.

This article examines in detail the characteristics of Dien Bien earthquake on 19 February 2001 and its aftershocks. On the basis of the temporal development of aftershocks and the spatial distribution of tectonic faults, five aftershock series have been determined. The analysis of spatial distribution and temporal evolution of these five aftershock series has clarified the development in the source zone of Dien Bien earthquake, which is closely related to the active and recent activities of tectonic faults in the area, especially Lai Chau Dien Bien fault. The comparison between characteristics of aftershock activities of Dien Bien earthquake and geomorphological features as well as tectonic activities in the area has indicated that the magnitude of these aftershocks and their temporal evolution (early or late) depend not only on the closer or further distance compared to the mainshock and the active faults that cause them but also on terrain elevation, slope index, lineament density and their positions relative to other tectonic faults in the studied area.

Geosynchronous (GEO) orbit and low-earth-orbit (LEO) in imaging have many differences, especially for relief of undulating three-dimensional(3D) terrain, the imaging errors caused by target elevation in two orbits of different altitudes are also diverse. The error caused by terrain elevation under the LEO SAR is negligible, and in GEO SAR the error will cause serious azimuth defocusing. This paper focuses on the error caused by topography elevation in LEO and GEO SAR respectively. Firstly, the SAR imaging geometric model including terrain elevation is established. Then, the source of error caused by terrain elevation and its influencing factors are analyzed. Finally, the error changes of the two orbits are analyzed, and the correctness of the proposed viewpoint is verified by experiments.

Forest surveillance towers have the advantages of long observation time, wide observation range, stable and real-time observation. In this paper, a multi-scale proposal regions fusion network (MFRPN) is proposed for detecting the infected trees automatically on the enhanced images from the forest surveillance towers, which can solve the problem that small and large targets can’t be effectively detected on a single scale. The proposed MFRPN includes multi-scale images, three CNNs, three different RPNs, and proposal regions fusion model. In the proposed method, we train and run the scale-specific detectors in a multi-task fashion. And, to obtain the accurate spatial level location information of the infected trees, we achieve the three-dimensional (3D) coordinates localization of the digital elevation model (DEM) by using the principle of forest surveillance towers imaging and terrain elevation data. The experimental results show the detection accuracy achieves 91.63%, the detection time of a single image is 0.46 second, and the 3D localization error is less than 50m. The proposed network can realize the real-time detection and 3D localization of the infected trees.

RADAR Altimeter Aiding (RALT Aiding) is an augmentation method to GPS to improve the standard GPS position solution accuracy, integrity, and continuity through the inclusion of an additional range measurement into the GPS measurement equation. This additional range measurement is derived through the combination of a radar altimeter and terrain elevation database. This paper extends on work previously competed by the authors and provides an in-depth introduction to the RALT Aiding method, description of work completed in the past, and outlook for the future of the concept.

The ability to recognize previously mapped locations is an essential feature for autonomous systems. Unstructured planetary-like environments pose a major challenge to these systems due to the similarity of the terrain. As a result, the ambiguity of the visual appearance makes state-of-the-art visual place recognition approaches less effective than in urban or man-made environments. This paper presents a method to solve the loop closure problem using only spatial information. The key idea is to use a novel continuous and probabilistic representations of terrain elevation maps. Given 3D point clouds of the environment, the proposed approach exploits Gaussian Process (GP) regression with linear operators to generate continuous gradient maps of the terrain elevation information. Traditional image registration techniques are then used to search for potential matches. Loop closures are verified by leveraging both the spatial characteristic of the elevation maps (SE(2) registration) and the probabilistic nature of the GP representation. A submap-based localization and mapping framework is used to demonstrate the validity of the proposed approach. The performance of this pipeline is evaluated and benchmarked using real data from a rover that is equipped with a stereo camera and navigates in challenging, unstructured planetary-like environments in Morocco and on Mt. Etna., This work is accepted for presentation at the 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). Please find IEEE's copyright statement at the bottom of the first page. Cedric Le Gentil and Mallikarjuna Vayugundla share the first authorship of this paper

The global digital elevation model (DEM) is important for various scientific applications. With the recently released TanDEM-X 90-m DEM and AW3D30 version 2.2, the open global or near-global coverage DEM datasets have been further expanded. However, the quality of these DEMs has not yet been fully characterized, especially in the application for regional scale studies. In this study, we assess the quality of five freely available global DEM datasets (SRTM-1 DEM, SRTM-3 DEM, ASTER GDEM2, AW3D30 DEM and TanDEM-X 90-m DEM) and one 30-m resampled TanDEM-X DEM (hereafter called TDX30) over the south-central Chinese province of Hunan. Then, the newly-released high precision ICESat-2 (Ice, Cloud, and land Elevation Satellite-2) altimetry points are introduced to evaluate the accuracy of these DEMs. Results show that the SRTM1 DEM offers the best quality with a Root Mean Square Error (RMSE) of 8.0 m, and ASTER GDEM2 has the worst quality with the RMSE of 10.1 m. We also compared the vertical accuracies of these DEMs with respect to different terrain morphological characteristics (e.g., elevation, slope and aspect) and land cover types. It reveals that the DEM accuracy decreases when the terrain elevation and slope value increase, whereas no relationship was found between DEM error and terrain aspect. Furthermore, the results show that the accuracy increases as the land cover type changes from vegetated to non-vegetated. Overall, the SRTM1 DEM, with high spatial resolution and high vertical accuracy, is currently the most promising dataset among these DEMs and it could, therefore, be utilized for the studies and applications requiring accurate DEMs.

The paper addresses the optimal bus stops allocation in the Laško municipality. The goal is to achieve a cost reduction by proper re-designing of a mandatory pupils’ transportation to their schools. The proposed heuristic optimization algorithm relies on data clustering and Monte Carlo simulation. The number of bus stops should be minimal possible that still assure a maximal service area, while keeping the minimal walking distances children have to go from their homes to the nearest bus stop. The working mechanism of the proposed algorithm is explained. The latter is driven by three-dimensional GIS data to take into account as much realistic dynamic properties of terrain as possible. The results show that the proposed algorithm achieves an optimal solution with only 37 optimal bus stops covering 94.6 % of all treated pupils despite the diversity and wideness of municipality, as well as the problematic characteristics of terrains’ elevation. The calculated bus stops will represent important guidelines to their actual physical implementation.

Viscously relaxed craters provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed craters in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the crater with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed craters indicates high heat flows—in excess of 30–40 mW m−2 over 2 Gyr, with many small (

According to the problem that the elevation data does not reflect the slope and surface roughness of target topography, the preprocessing of topographic elevation data and extraction algorithm of topographic feature are proposed, and the corresponding extraction of topographic feature is done. A terrain risk assessment method is presented based on terrain roughness and slope information fusion, aiming at the problem that terrain roughness and gradient cannot be directly reflected from the terrain elevation data, in this paper. The innovation is that it is the first time that the bilinear interpolation algorithm is applied in preprocess of elevation data and extraction of topographic feature, as well as the terrain roughness and gradient information fusion algorithm are applied to terrain feature extraction and risk assessment for the first time. By simulation and checking calculation of a certain digital topography example, it is proved that the extraction method of topographic information based on elevation data is feasible and reliable. It will provide a new research approach for target information recognition and topography risk assessment accurately.

This paper is devoted to the method for a three-dimensional radar image restoration of terrain elevations using airborne two antenna interferometric frequency-domain radar. A method’s main feature is the parallel obtaining of two-dimensional frequencydomain spectra both of radar terrain echo and its derivative for next synthesizing. The architecture of such interferometric radar is proposed, and math equations for one’s performance calculation are presented. The numerical algorithm for the terrain elevations calculation over an arbitrary horizontal plane is developed.

A vision-based navigation approach using digital terrain elevation data and a monocular camera is addressed for autonomous navigation of unmanned aircraft. Previous vision-based terrain-referenced navigation algorithms use visual measurements to update vehicle position. This study expands the use of the visual measurements and the terrain data by designing the navigation filter to update 3-axis attitude and velocity as well as position. An observation model for updating position and attitude compares height estimates of ground features, computed from the visual measurements, with terrain elevation data. Additionally, the eight-point algorithm is adopted to extract direction of camera movement to update velocity in the navigation filter. A simulation study is conducted to verify the feasibility of the proposed method and the effect of visual measurement errors.

Fiji is prone to the devastating effects of heavy rainfall during the passage of tropical cyclones (TCs) and as such accurate measurement of rainfall during such events is urgent for effective disaster mitigation and risk analysis. Fiji, however, has a sparse distribution of rain gauges, thus there is a deficiency in the accurate measurement of rainfall. This gap could be filled by satellite-based rainfall estimates but before they are used, they need to be validated against a reference dataset for their accuracy and limitations. This study thus validates the TRMM based Multi-satellite Precipitation Analysis (TMPA) estimates over the island of Fiji. The study shows that TMPA has moderate skill in estimating rainfall during the passage of TCs over the island of Fiji. This skill is also highly variable as it decreases with an increase in rainfall intensity, increase in distance from the cyclone centre and increasing terrain elevation. The ability of TMPA also varies case by case but we report a general underestimation of rainfall by TMPA during the passage of TCs with a larger rainfall rate (defined in our case as those TCs with average daily rainfall greater than 25 mm day-1).

Wind energy as a power source is an attractive alternative to fossil fuels. Globally, an increasing number of wind farms is being planned and constructed. The conditions of highway design indexes for wind farms are unique, and the current design standards are not appropriate for determining the necessary critical lengths of grade. The relative vehicle parameters for aerogenerator transportation are investigated in detail, and the typical design vehicle for aerogenerator transportation is selected. The dynamic characteristics, such as acceleration and deceleration performances, are analysed based on the nominal dynamic, kinematic and operating characteristics of the typical vehicle on wind farm grades and terrain elevation. This study proposes a formulation to obtain the relation between speed and distance travelled for heavier design vehicles, from which speed-gain and speed-drop curves are calculated and drawn. In addition, the total accumulative speed–distance profiles with different gears are also combined. Through an extensive calculation, this paper also provides practitioners with design tables for the maximum critical length of typical design vehicles for large aerogenerator transportation under full load and 80 t load. The research results can serve as a reference for aerogenerator transportation highway design and construction and are helpful for related highway geometric design guidelines.

With the increase in computational power and the emergence of a large number of digital data, the role of new methods and technologies in urban planning is becoming more and more important. The characteristics of the parametric design method determine its practicality and development potential in dealing with the planning and design of complex systems such as cities. Based on the concept and innovative ideas on urban planning, this paper adopts the methods of parametric technology to define the main measures and technological route. Also, based on the research methods of parametric technology, the platform of combining Rhino and Grasshopper can be used for the analysis on terrain elevation, contour, slope, sunshine and surface runoff. With this chance, this paper hopes to provide a rational and scientific aid for the implementation of urban planning at a later period.

Based on the DEM grid image of "sanjiangyuan" region and the temperature data of 16 meteorological stations from 1951 to 2010, this paper calculated and processed the topographic fluctuation, elevation standard deviation and surface roughness indexes representing topographic heterogeneity, and analyzed the impact of topographic heterogeneity on local climate and other aspects. The results show that the overall terrain elevation of "sanjiangyuan" region is high, the surface fluctuation is large, and the south and southeast of the region are the places with the most drastic topographic changes, and the absolute value of topographic fluctuation, elevation standard deviation and surface roughness are all large. In the central and western regions, the terrain changes little, the relief degree is small, the elevation standard deviation and the surface roughness are also small. In the whole study area, the climate in the area with similar latitude was significantly affected by terrain heterogeneity. The climate in the area with large terrain heterogeneity was correspondingly characterized by warmer and wetter, more precipitation and higher temperature.

This paper studies positioning issue in navigation using InSAR concept. A novel method based on wrapped interferometric phase registration, which differs from common InSAR based navigation method, is proposed. This method may be useful when navigating throw hills or areas with low SAR image characteristics but rich terrain elevation features. Accurate DEM data is needed to generate ideal interferometric phase template for registration. Three dimensional positioning is achieved by estimating vertical bias and horizontal bias in order. The proposed method works well under different squint angle. Simulations are carried out to verify the method. Precision of the method under different squint angle is also exhibited in simulations.

Creative content requires a lot of human resources. Computational creativity gets more attention as computational resources are getting fast enough to quickly create automated content with enough precision and similarity to human-created digital assets. Paper explores terrain generation methods and proposes a different solution to generate mountains. A landscape is created using voxel-based cubes and the base map is modified using generation agents. Vertical points are extended and filled using arithmetic operations between arrays for each vertical point. Height normalization is applied to remove rare mountain elevation layers.

Topography derived using human-portable unmanned aerial vehicles (UAVs) and structure from motion photogrammetry offers an order of magnitude improvement in spatial resolution and uncertainty over small survey extents, compared to global digital elevation model (DEM) products, which are often the only available choice of DEMs in the high-mountain Himalaya. Access to fine-resolution topography in the high mountain Himalaya is essential to assess where flood and landslide events present a risk to populations and infrastructure. In this study, we compare the topography of UAV-derived DEMs, three open-access global DEM products, and the 8 m High Mountain Asia (HMA) DEMs (released in December 2017) and assess their suitability for landslide- and flood-related hazard assessments. We observed close similarity between UAV and HMA DEMs when comparing terrain elevation, river channel delineation, landside volume, and landslide-dammed lake area and volume. We demonstrate the use of fine-resolution topography in a flood-modelling scenario relating to landslide-dammed lakes that formed on the Marsyangdi River following the 2015 Gorkha earthquake. We outline a workflow for using UAVs in hazard assessments and disaster situations to generate fine-resolution topography and facilitate real-time decision-making capabilities, such as assessing landslide-dammed lakes, mass movement volumes, and flood risk.

Precipitation diurnal cycle over Fujian in the pre-summer rainy season has been revealed based on the hourly rain gauge data during 2009–2013. The precipitation amount (PA) over northwestern Fujian and most southeast coasts shows relatively small diurnal variability. This is in contrast to large diurnal variations in the mountainous areas. Regional differences in precipitation diurnal cycles are obviously noted among the coastal, valley, hilly, and mountainous areas. The precipitation diurnal cycles are significantly affected by the terrain elevation and distance to coast, PA and precipitation frequency (PF) show much more pronounced double diurnal peaks with the terrain elevation and distance to coast increased. However, the precipitation intensity (PI) basically shows one distinct late afternoon diurnal peak for different elevations and distances to coast. Four typical patterns of precipitation diurnal cycle are further identified by cluster analysis. The four typical PF patterns show relatively apparent morning peaks over coasts, inland mountains, and hills in addition to distinct late afternoon maxima. Low PF with weak diurnal amplitude is mainly located over the coastal areas, while high PF with strong diurnal amplitude is found over the valley, hilly, and mountainous regions. The PA exhibits a weak early morning peak and a relatively strong late afternoon peak over coastal, hilly, or mountainous areas and windward slopes but only one distinct late afternoon peak over the valley regions and leeward slopes. The amplitude of PA diurnal cycle is the weakest over the coastal areas but the strongest over the valley regions or leeward slopes among the four PA patterns. The four PI diurnal cycle patterns consistently show distinct afternoon peaks.

The roll stability is significant for both road and off-road commercial vehicles, while the majority of reported studies focus on road vehicles neglecting the contributions of uneven off-road terrains. The limited studies on roll stability of off-road vehicles have assessed the stability limits using performance measures derived for road vehicles. This study proposes an alternative performance measure for assessing roll stability limits of off-road vehicles. The roll dynamics of an off-road mining vehicle operating on random rough terrains are investigated, where the two terrain-track profiles are synthesized considering coherency between them. It is shown that a measure based on steady-turning root-mean-square lateral acceleration corresponding to the sustained period of unity lateral-load-transfer-ratio prior to the absolute-rollover, could serve as a reliable measure of roll stability of the vehicle operating on random rough terrains. The robustness of proposed performance measure is demonstrated considering sprung mass center height variations and different terrain excitations. The simulation results revealed adverse effects of terrain elevation magnitude on the roll stability, while a relatively higher coherency resulted in lower terrain roll-excitation and thereby enhanced vehicle roll stability. Terrains with relatively higher waviness increased the magnitude of lower spatial frequency components, which resulted in reduced roll stability limits.

Terrain synthesis has been a hot topic in the field of computer graphics and image processing. However, there are still issues in terrain synthesis where synthesis results are difficult to control and not realistic enough. To address these problems, this paper proposes an interactive terrain elevation map generation method based on the synthesis of a single sample terrain elevation map. First, we propose a method to extract the skeleton from a terrain elevation map and a user sketch. Second, we construct a skeleton sample feature map based on the terrain elevation map and the user sketch. Finally, we propose a matching cost function to match image patches of the terrain sample and the user sketch. The proposed method can obtain a synthesis result containing the features of both the terrain sample and the user sketch, and then generates a synthetic terrain elevation map. The experimental results demonstrate the effectiveness of the proposed method, where the synthesized results can meet the needs of users.

Intensive development of South Yakutia, a mountainous area in the Russian sporadic permafrost zone, must be founded on knowledge about regional permafrost conditions. New permafrost maps for mountainous areas in South Yakutia (the Elkon Mountains and the Olekma-Chara Upland) are presented that provide a more detailed and updated description of permafrost distribution in the area than those that were hitherto available. These maps are based on the previously-developed and tested method of detecting permafrost and unfrozen ground using Landsat-5/TM satellite data with relatively high resolution. The method represents a scheme for permafrost identification based on a set of landscape indicators: terrain elevation, slope angle and exposition, vegetation, snow cover, and land surface temperature (LST). A correlation analysis of satellite data to full-scale field data has been carried out for the two areas under consideration. Indicator properties of LST obtained by Landsat-5/TM Band 6 Infrared have been characterized in detail for detection and regional mapping of permafrost. The effect of landscape factors (landscape cryo-indicators) on ground temperature and condition, frozen or unfrozen reflected in LST intensity, is demonstrated.

In the present study, spatial and temporal patterns of rain event properties are analysed. These event properties are rain event depth, event duration, mean event rain rate, peak rain rate and the time span between two consecutive rain events which is referred to as inter-event time (IET). In addition, we assessed how rain event properties change when the period over which rainfall data is aggregated changes from 1 to 6 min and when the minimum inter-event time (MIT) changes from 30 min to 8 h. Rainfall data is obtained from a field campaign in two wet seasons of June–August (JJA) of 2007 and 2008 in Gilgel Abbay watershed that is situated at the source basin of the Upper Blue Nile River in Ethiopia. The rainfall data was automatically recorded at eight stations. The results revealed that rain event depth is more related to peak rain rate than to event duration. At the start and towards the end of the wet season, the rain events have larger depth with longer duration and longer IET than those in mid-season. Event rain rate and IET are strongly related to terrain elevation. Sekela which is on a mountain area has the shortest IET while Bahir Dar which is at the south shore of Lake Tana has the longest IET. The period over which rainfall data is aggregated significantly affected the values of rain event properties that are estimated using relatively small value (30 min) of MIT but its effect diminished when the MIT is increased to 8 h. It is shown that increasing the value of MIT has the largest effect on rain event properties of mountain stations that are characterised by high rainfall intermittency.

Topography is a key driver of tropical forest structure and composition, as it constrains local nutrient and hydraulic conditions within which trees grow. Yet, we do not fully understand how changes in forest physiognomy driven by topography impact other emergent properties of forests, such as their aboveground carbon density (ACD). Working in Borneo – at a site where 70‐m‐tall forests in alluvial valleys rapidly transition to stunted heath forests on nutrient‐depleted dip slopes – we combined field data with airborne laser scanning and hyperspectral imaging to characterise how topography shapes the vertical structure, wood density, diversity and ACD of nearly 15 km2 of old‐growth forest. We found that subtle differences in elevation – which control soil chemistry and hydrology – profoundly influenced the structure, composition and diversity of the canopy. Capturing these processes was critical to explaining landscape‐scale heterogeneity in ACD, highlighting how emerging remote sensing technologies can provide new insights into long‐standing ecological questions.