Detailed Terrain Models Research Articles

Morfológiai vizsgálatok Magyarország délnyugati határfolyóin = Morphological Studies on South-Western Border Rivers in Hungary

Nowadays, the preservation and sustainable use of our natural values are increasingly coming to the fore, and this has implications not only for economic and field development but also for ecological aspects. In recent years, attention has shifted towards river morphological studies, which were previously relegated to the background. Understanding long-term changes and assessing the current state is essential to estimate future processes. In this article, we present our morphological studies on the Hungarian–Croatian border sections of the Mura and the Drava rivers. Historical changes were analyzed through a comparative study of historical maps from earlier periods, while the evaluation of the current state was conducted based on a detailed terrain model from a recent survey. GIS evaluation was also compared with sediment transport and flow measurement results. This comparison suggests that the morphological status of the river section under study is consistent with the typical parameters of transport processes.

Quality Analysis of 3D Models Based on Digital Photogrammetry

The main focus of the paper is the assessment of the quality of the 3D terrain models obtained from the images of unmanned aerial vehicles (UAV). Quality and detailed terrain models are necessary, above all, for precise determination of changes in the area of excavation. The quality analysis of the 3D model includes the degree of deviation of geometric and geomorphological characteristics from the actual terrain position and status in nature. To determine the geometric accuracy, a comparative method of testing is used, ie a comparison of the measured values of the 3D model with the data of well-defined geodetic and control points a posteriori measured using the Global Navigation Satellite Systems (GNSS). Analysis of quality and comparisons are performed visually, numerically, by calculating the excavation volume and creating a terrain profile. The results suggest that the 3D models obtained from the UAV images are of very high quality. Also, an important advantage of using UAV images to generate 3D models in the excavation area is their efficiency, for example, more frequent updating and measuring the height of inaccessible terrain and determining local changes in the terrain.

Impact-Detection Algorithm That Uses Point Clouds as Topographic Inputs for 3D Rockfall Simulations

Numerous 3D rockfall simulation models use coarse gridded digital terrain model (DTM raster) as their topography input. Artificial surface roughness is often added to overcome the loss of details that occurs during the gridding process. Together with the use of sensitive energy damping parameters, they provide great freedom to the user at the expense of the objectivity of the method. To quantify and limit the range of such artificial values, we developed an impact-detection algorithm that can be used to extract the perceived surface roughness from detailed terrain samples in relation to the size of the impacting rocks. The algorithm can also be combined with a rebound model to perform rockfall simulations directly on detailed 3D point clouds. The abilities of the algorithm are demonstrated by objectively extracting different perceived surface roughnesses from detailed terrain samples and by simulating rockfalls on detailed terrain models as proof of concept. The results produced are also compared to that of rockfall simulation software CRSP 4, RocFall 8 and Rockyfor3D 5.2.15 as validation. Although differences were observed, the validation shows that the algorithm can produce similar results. With the presented approach not being limited to coarse terrain models, the need for adding artificial terrain roughness or for adjusting sensitive damping parameters on a per-site basis is reduced, thereby limiting the related biases and subjectivity.

Holoceńskie okresy intensyfikacji procesów stokowych w Gorcach – porównanie najnowszych wyników badań = Periods of intensified hillslope processes in Poland’s Gorce Mountains during the Holocene – a comparison based on new data

This paper presents selected results from efforts to date organic matter taken from deposits of three landslides in Poland’s Gorce Mts. i.e. the ones located below the Jaworzyna Kamienicka, Kudłoń and Góra Gębowa peaks. The material for dating was taken from two landslide peat bogs and one closed depression filled with mineral deposits. The ranges of the individual landslides were analysed by reference to a detailed terrain model as well as geophysical tests, while the organic samples collected were 14C radiocarbon-dated. The borehole drilled in the landslide below Jaworzyna Kamienicka reaches a depth of 2.2 m. It was from that profile that samples for 14C radiocarbon-dating, as well as palaeobotanical and geochemical study, were taken. The oldest deposits on the floor part of the peatland were dated to 8060±100 BP (8949 cal BP). The first level of gravels mixed with so-called organic chaff was dated to 7950±80 BP (8802 cal BP) and is deposited directly beneath a layer of peats dated to 75600±100 BP (8366 cal BP). Another important layer is of gravel and fragments of wood, 9 cm thick, deposited at a level dated to 3999±60 BP (4517 cal BP). Three boreholes were drilled in the peat bog below Kudłoń, with the oldest peat deposits at this site are dated to 5430±70 BP (6002 cal BP), and situated at a depth of 100‑80 cm. In the other two places deposits in the floor profile were dated to 3010±60 BP and 400±60 BP. No mineral levels nor levels with a high share of mineral parts were found. Into the landslide below Góra Gębowa eight boreholes were made within a closed depression filled with mineral deposits. A fragment of wood taken from borehole 5 at a depth of 2.2 m was dated to 8850±100 BP (9739 cal BP), while one from a depth of 1 m is associated with a date of 8070±100 BP (8959 cal BP). In turn, the floor of borehole 6, at a depth of 2.1 m was the source for a wood sample of determined age equal to 8440±110 BP (9329 cal BP). The oldest deposits in the Gorce Mts. are of a fen character and area aged 9500 ± 90 BP (11 143‑10 653 cal BP). They come from the Turbacz Range. The next landslide phase is confirmed by wood fragments from the landslide below Góra Gębowa (8850±100 BP, 9739 cal BP), and could also be linked with rise of C. avellana within forest structure, as well as with the period of intense mineral-material deposition reported from four places in Makowski Beskid Mts. A following phase of landslide formation is confirmed by data from Jaworzyna Kamienicka (8060±100 BP, 8949 cal BP) and Lake Zawadowskie (7947‑7685 cal BP, Buczek, 2019), and represents the effect of the increased humidity and cooling of the climate reported from the Western Carpathians by many researchers. The oldest deposits from the peat bog below Kudłoń date to 5430±70 BP (6002 cal BP). Such a result is consistent with the increase in organic matter in Lake Zawadowskie in this period (5420± 60 BP). The traces from that period recorded by Buczek (2019), and the dating of deposits beneath Kudłoń, may both indicate that a period 6.0‑5.5 ka cal BP was the next one in which morphogenetic activity in the Gorce Mts. increased. The formation of the Lelonek landslide (401 ±70 BP) could be treated as evidence of a next landslide-creation phase (Buczek, 2019) also gaining confirmation from Margielewski (2018). There is also a gravel-wood level in the core from Jaworzyna Kamiecka dated at 3999±60 BP; 4517 cal BP. Kołaczek et al. (2020) noted a major change of forest structure with increases of A. alba, F. sylvatica and C. betulus at ~4.0 ka BP (~4.5 ka cal BP). This attests to the period in question being one characterized by a high level of landslide activity. Comparison of all the latest data from the region in question sustains the conclusion that ~11.1 ka cal BP, ~9.7 cal BP, 8.6‑8.0 cal BP, ~6,0 cal BP and ~4.5 ka cal BP, 3.3‑2.5 cal BP and 1.75‑1.35 cal BP are all periods associated with intensified Holocene landslide movements in the Gorce Mountains.

Digital photogrammetric analysis approaches for the realization of detailed terrain models

Digital Surface Models (DSMs) with a high spatial resolution and accuracy are of increasing importance for many applications. Recent advances in data acquisition technologies, such as those related to the use of Unmanned Aerial Vehicles (UAVs), enabled the acquisition of images suitable to generate high-resolution DSMs. The present study aims to provide useful indications for data acquisition and processing to obtain DSMs with small errors by using the Structure from Motion (SfM) algorithm. We changed three parameters during data acquisition (flight height, camera type and acquisition mode) and used four different interpolation methods in the elaboration phase (Inverse Distance Weighted - IDW, IDW ArcGIS, Triangular Irregular Network – TIN, and Topo to Raster). Obtained results highlight the advantage to use the IDW method for data interpolation and for areas of various surface in combination with different flight heights as follows: i) for areas smaller than 0.1 ha, a flight altitude of 5 meters is advisable; ii) for areas between 0.1 and 1 ha, a flight altitude of 15 meters is advisable; iii) for areas larger than 1 ha, the most convenient flight altitude is 30 meters. Our workflow can also be followed by different tools (RGB cameras, light detection and ranging - LIDAR) to obtain the best DSMs accuracy.

Morphometric analysis of debris flows basins in the Eastern Rhodopes (Bulgaria) using geospatial technologies

Debris flows are considered as a rapid movement of highly water-saturated colluvial and proluvial deposits. Besides the intensive rainfall and snowmelt, there are several other factors—prerequisites to debris flows: morphometric characteristics, rocks composition, active tectonics and deforestation. The current research is directed to the analysis of morphometric parameters of debris flow areas located in Eastern Rhodopes (Bulgaria). Two types of debris flows are analysed—gully-induced debris flows and stream torrent section with debris flood occurrence. The aim is to determine morphometric indicators to be used for discrimination of debris flow types and further susceptibility assessment. The following parameters are calculated: basin area and length, basin relief, relief ratio, Melton index, slope, topographic wetness index, stream power index and curvature. The analysis shows that slopes in a range 30–45° have most important role, among the other topographic factors, for debris flow initiation. Melton index is a meaningful indicator for discrimination of debris flow types. It is greater than 1 at gully-induced debris flows and much lower at the debris flood section (0.14–0.16). The analysis of curvature rasters, generated as a second derivative of digital elevation model (DEM), shows that the considered gullies are subject of intensive erosion and the process is still active. The research is elaborated in GIS environment on the basis of DEM and field investigations. Terrestrial laser scanning (TLS) of the low part of the basins and debris flow fan is done, and detailed terrain models are developed for the purpose of morphometric analyses.

Quantifying Flood Water Levels Using Image-Based Volunteered Geographic Information

Many people use smartphone cameras to record their living environments through captured images, and share aspects of their daily lives on social networks, such as Facebook, Instagram, and Twitter. These platforms provide volunteered geographic information (VGI), which enables the public to know where and when events occur. At the same time, image-based VGI can also indicate environmental changes and disaster conditions, such as flooding ranges and relative water levels. However, little image-based VGI has been applied for the quantification of flooding water levels because of the difficulty of identifying water lines in image-based VGI and linking them to detailed terrain models. In this study, flood detection has been achieved through image-based VGI obtained by smartphone cameras. Digital image processing and a photogrammetric method were presented to determine the water levels. In digital image processing, the random forest classification was applied to simplify ambient complexity and highlight certain aspects of flooding regions, and the HT-Canny method was used to detect the flooding line of the classified image-based VGI. Through the photogrammetric method and a fine-resolution digital elevation model based on the unmanned aerial vehicle mapping technique, the detected flooding lines were employed to determine water levels. Based on the results of image-based VGI experiments, the proposed approach identified water levels during an urban flood event in Taipei City for demonstration. Notably, classified images were produced using random forest supervised classification for a total of three classes with an average overall accuracy of 88.05%. The quantified water levels with a resolution of centimeters (<3-cm difference on average) can validate flood modeling so as to extend point-basis observations to area-basis estimations. Therefore, the limited performance of image-based VGI quantification has been improved to help in flood disasters. Consequently, the proposed approach using VGI images provides a reliable and effective flood-monitoring technique for disaster management authorities.

Multi-theme generative adversarial terrain amplification

Achieving highly detailed terrain models spanning vast areas is crucial to modern computer graphics. The pipeline for obtaining such terrains is via amplification of a low-resolution terrain to refine the details given a desired theme, which is a time-consuming and labor-intensive process. Recently, data-driven methods, such as the sparse construction tree, have provided a promising direction to equip the artist with better control over the theme. These methods learn to amplify terrain details by using an exemplar of high-resolution detailed terrains to transfer the theme. In this paper, we propose Generative Adversarial Terrain Amplification (GATA) that achieves better local/global coherence compared to the existing data-driven methods while providing even more ways to control the theme. GATA is comprised of two key ingredients. Thefi rst one is a novel embedding of themes into vectors of real numbers to achieve a single tool for multi-theme amplification. The theme component can leverage existing LIDAR data to generate similar terrain features. It can also generate newfi ctional themes by tuning the embedding vector or even encoding a new example terrain into an embedding. The second one is an adversarially trained model that, conditioned on an embedding and a low-resolution terrain, generates a high-resolution terrain adhering to the desired theme. The proposed integral approach reduces the need for unnecessary manual adjustments, can speed up the development, and brings the model quality to a new level. Our implementation of the proposed method has proved successful in large-scale terrain authoring for an open-world game.

Large‐Scale Pixel‐Precise Deferred Vector Maps

AbstractRendering vector maps is a key challenge for high‐quality geographic visualization systems. In this paper, we present a novel approach to visualize vector maps over detailed terrain models in a pixel‐precise way. Our method proposes a deferred line rendering technique to display vector maps directly in a screen‐space shading stage over the 3D terrain visualization. Due to the absence of traditional geometric polygonal rendering, our algorithm is able to outperform conventional vector map rendering algorithms for geographic information systems, and supports advanced line anti‐aliasing as well as slope distortion correction. Furthermore, our deferred line rendering enables interactively customizable advanced vector styling methods as well as a tool for interactive pixel‐based editing operations.

The Role of Topography in the Distribution and Intensity of Damage Caused by Deer in Polish Mountain Forests.

The increase in the deer population observed in recent decades has strongly impacted forest regeneration and the forest itself. The reduction in the quality of raw wood material, as a consequence of deer-mediated damage, constitutes a significant burden on forest owners. The basis for the commencement of preventive actions in this setting is the understanding of the populations and behaviors of deer in their natural environment. Although multiple studies have been carried out regarding this subject, only a few suggested topography as an important factor that may influence the distribution and intensity of deer-mediated damage. The detailed terrain models based on LiDAR data as well as the data on damage caused by deer from the State Forests database enabled thorough analyses of the distribution and intensity of damage in relation to land form in this study. These analyses were performed on three mountain regions in Poland: the Western Sudety Mountains, the Eastern Sudety Mountains, and the Beskidy Mountains. Even though these three regions are located several dozen to several hundred kilometers apart from each other, not all evaluated factors appeared common among them, and therefore, these regions have been analyzed separately. The obtained results indicated that the forest damage caused by deer increased with increasing altitude above 1000 m ASL. However, much larger areas of damage by deer were observed at elevations ranging from 401 to 1000 m ASL than at elevations below 400 m ASL. Moreover, the locations of damage (forest thickets and old stands) indicated that red deer is the species that exerts the strongest pressure on forest ecosystems. Our results show the importance of deer foraging behavior to the structure of the environment.

Assessment of sediment sources throughout the proglacial area of a small Arctic catchment based on high-resolution digital elevation models

The article presents calculations of quantitative modifications of the morphology of selected subsystems of a glacial valley through: (i) identification of the spatial distribution of important sources of sediment, (ii) assessment of the spatiotemporal variety of sediment volume and landform morphology, and (iii) assessment of the role of particular subsystems in sediment distribution. The study involved a comparison of the results of field measurements from 2010 to 2013 performed in the Scott Glacier catchment (10.1km2) in NW Wedel Jarlsberg Land (Spitsbergen). The assessment of the landform surface changes was performed by means of a precise Terrestrial Laser Scanning (TLS) survey. The applied field and post-processing techniques for oblique laser scanning permitted the acquisition of digital elevation data at a resolution 0.01m and density>500ptm−2. This allowed the development of a detailed terrain model, and balancing spatial quantitative changes in six research test areas (10,000m2) located within two subsystems of the catchment in a cascade arrangement. In the alluvial valley-floor subsystem, the survey covered: 1) the glacier terminus, 2) the intramarginal outwash plain, 3) the extramarginal braid-plain and 4) the alluvial fan, and in the slope subsystem: 5) the erosional-depositional slope in the gorge through terminal moraines, and 6) the solifluction slope. Three zones differing in terms of the spatiotemporal dynamics of geomorphic processes were distinguished within the two analysed valley subsystems. In the valley floor subsystem, these are: (i) the zone of basic supply (distribution throughout the melting season) and (ii) the redeposition zone (distribution particularly during floods), and in the slope subsystem: (iii) zone of periodical supply (distributed mainly in periods of increased precipitation and rapid increases in temperature in summer and during snow avalanches in winter). The glacier and the landforms of the channel and valley floor, as well as slope sediments transported as a result of mass wasting processes and activity of the active permafrost layer, constitute important sources of sediment supply over a short/3-year timescale. Evidence of major changes of the surface morphology (slopes, floodplain and channel platform) resulted in varied sediment budgets. The subtraction of consecutive DEMs of the test areas located in the alluvial valley subsystem revealed downstream spatial and volumetric differentiation, from the predominance of erosion (79% of volume; 43% of area) to the dominance of deposition (90/91%, respectively) in upper part of the valley floor to erosion predominance in the central (88/95%) and lower (87/82%) part of valley floor. The test areas located on the slope subsystem showed the opposite relationship: deposition dominance (88% of volume; 80% of area) in the upper gorge and erosion dominance (99/99%, respectively) in the lower part (solifluction slopes). The analysis of short-time repeated surveys (3-week survey) where volumes were calculated following DEM subtraction showed increased deposition (82% of volume; 79% of area) for the alluvial fan, and for solifluction slopes (70/57%, respectively).

A new architecture for efficient hybrid representation of terrains

Interactive visualization of highly detailed terrain models is a challenging problem as the size of the data sets can easily exceed the capabilities of current hardware. Hybrid representation of terrains tries to solve the problem by combining the advantages in terms of reduced size associated with multiple levels-of-detail of digital elevation models with the high quality associated with the triangulated irregular networks. However, as the measurements of both representations have different origins, a direct representation of the hybrid system would result in discontinuities. In this paper, we present an architecture for hybrid representation of terrains based on a local convexification algorithm. The architecture we propose permits the generation of the additional triangles required to join the models and thereby avoid the discontinuities. The architecture is simple and regular and a high triangle generation rate is achieved. Different optimizations have been performed that avoid waiting cycles between tessellator units and so increase the productivity rate of the system. Implementation results are shown for a Virtex-II FPGA as an application example.

A system for wind power estimation in mountainous terrain. Prediction of Askervein hill data

AbstractIn mountainous terrain, where the wind power potential is largest, the estimation of the local wind power can be done rationally by means of available information about the large‐scale flow and the detailed terrain and numerical flow models for downscaling, provided that the numerical model estimates can be assigned sufficient confidence. In this study the confidence of a local model in such an estimation system is discussed. The model is based upon the Reynolds‐averaged Navier–Stokes equations with (K, ϵ) turbulence closure and integrated with finite element numerical techniques. The model has previously been validated relative to complicated laboratory‐scale flows and appears to predict some full‐scale geophysical flows plausibly. Here its predictions are compared quantitatively with the full‐scale Askervein hill experimental data. The model estimates the data to within the experimental uncertainty, which we judge to be comparable to 10%, as other comparable models also do. This contributes to assign confidence to the downscaling estimation system mentioned. Copyright © 2004 John Wiley & Sons, Ltd.

Flight test results from a strapdown airborne gravity system

In June 1995, a flight test was carried out over the Rocky Mountains to assess the accuracy of airborne gravity for geoid determination. The gravity system consisted of a strapdown inertial navigation system (INS), two GPS receivers with zero baseline on the airplane and multiple GPS master stations on the ground, and a data logging system. To the best of our knowledge, this was the first time that a strapdown INS has been used for airborne gravimetry. The test was designed to assess repeatability as well as accuracy of airborne gravimetry in a highly variable gravity field. An east-west profile of 250 km across the Rocky Mountains was chosen and four flights over the same ground track were made. The flying altitude was about 5.5km, i.e., between 2.5 and 5.0km above ground, and the average flying speed was about 430km/h. This corresponds to a spatial resolution (half wavelength of cutoff frequency) of 5.07.0km when using filter lengths between 90 and 120s. This resolution is sufficient for geoid determination, but may not satisfy other applications of airborne gravimetry. The evaluation of the internal and external accuracy is based on repeated flights and comparison with upward continued ground gravity using a detailed terrain model. Gravity results from repeated flight lines show that the standard deviation between flights is about 2mGal for a single profile and a filter length of 120s, and about 3mGal for a filter length of 90s. The standard deviation of the difference between airborne gravity upward continued ground gravity is about 3mGal for both filter lengths. A critical discussion of these results and how they relate to the different transfer functions applied, is given in the paper. Two different mathematical approaches to airborne scalar gravimetry are applied and compared, namely strapdown inertial scalar gravimetry (SISG) and rotation invariant scalar gravimetry (RISG). Results show a significantly better performance of the SISG approach for a strapdown INS of this accuracy class. Because of major differences in the error model of the two approaches, the RISG method can be used as an effective reliability check of the SISG method. A spectral analysis of the residual errors of the flight profiles indicates that a relative geoid accuracy of 23cm over distances of 200km (0.1 ppm) can be achieved by this method. Since these results present a first data analysis, it is expected that further improvements are possible as more refined modelling is applied.