scholarly journals The Effect of LiDAR Sampling Density on DTM Accuracy for Areas with Heavy Forest Cover

Forests ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 265
Author(s):  
Mihnea Cățeanu ◽  
Arcadie Ciubotaru
Keyword(s):  
Forest Cover ◽  
Initial Point ◽  
Ground Surface ◽  
Digital Terrain Model ◽  
Morphological Data ◽  
Sampling Density ◽  
Terrain Model ◽  
Digital Terrain ◽  
Point Density ◽  
The Impact

Laser scanning via LiDAR is a powerful technique for collecting data necessary for Digital Terrain Model (DTM) generation, even in densely forested areas. LiDAR observations located at the ground level can be separated from the initial point cloud and used as input for the generation of a Digital Terrain Model (DTM) via interpolation. This paper proposes a quantitative analysis of the accuracy of DTMs (and derived slope maps) obtained from LiDAR data and is focused on conditions common to most forestry activities (rough, steep terrain with forest cover). Three interpolation algorithms were tested: Inverse Distance Weighted (IDW), Natural Neighbour (NN) and Thin-Plate Spline (TPS). Research was mainly focused on the issue of point data density. To analyze its impact on the quality of ground surface modelling, the density of the filtered data set was artificially lowered (from 0.89 to 0.09 points/m2) by randomly removing point observations in 10% increments. This provides a comprehensive method of evaluating the impact of LiDAR ground point density on DTM accuracy. While the reduction of point density leads to a less accurate DTM in all cases (as expected), the exact pattern varies by algorithm. The accuracy of the LiDAR-derived DTMs is relatively good even when LiDAR sampling density is reduced to 0.40–0.50 points/m2 (50–60 % of the initial point density), as long as a suitable interpolation algorithm is used (as IDW proved to be less resilient to density reductions below approximately 0.60 points/m2). In the case of slope estimation, the pattern is relatively similar, except the difference in accuracy between IDW and the other two algorithms is even more pronounced than in the case of DTM accuracy. Based on this research, we conclude that LiDAR is an adequate method for collecting morphological data necessary for modelling the ground surface, even when the sampling density is significantly reduced.

scholarly journals UAV-based mapping, back analysis and trajectory modeling of a coseismic rockfall in Lefkada island, Greece

2018 ◽  
Vol 18 (1) ◽  
pp. 321-333 ◽  
Author(s):  
Charalampos Saroglou ◽  
Pavlos Asteriou ◽  
Dimitrios Zekkos ◽  
George Tsiambaos ◽  
Marin Clark ◽  
...  
Keyword(s):  
Back Analysis ◽  
Ground Surface ◽  
Digital Terrain Model ◽  
Engineering Practice ◽  
Terrain Model ◽  
Digital Terrain ◽  
Field Evidence ◽  
Kinematic Study ◽  
Lefkada Island ◽  
The Impact

Abstract. We present field evidence and a kinematic study of a rock block mobilized in the Ponti area by a Mw = 6.5 earthquake near the island of Lefkada on 17 November 2015. A detailed survey was conducted using an unmanned aerial vehicle (UAV) with an ultrahigh definition (UHD) camera, which produced a high-resolution orthophoto and a digital terrain model (DTM). The sequence of impact marks from the rock trajectory on the ground surface was identified from the orthophoto and field verified. Earthquake characteristics were used to estimate the acceleration of the rock slope and the initial condition of the detached block. Using the impact points from the measured rockfall trajectory, an analytical reconstruction of the trajectory was undertaken, which led to insights on the coefficients of restitution (CORs). The measured trajectory was compared with modeled rockfall trajectories using recommended parameters. However, the actual trajectory could not be accurately predicted, revealing limitations of existing rockfall analysis software used in engineering practice.

scholarly journals Mapping of slopes for the operation of agricultural harvesters in Bandeirantes Municipality (PR)

2017 ◽  
Vol 38 (1) ◽  
pp. 97
Author(s):  
Gustavo Rodrigues Gimenes ◽  
Rone Batista Oliveira ◽  
Alessandra Fagioli da Silva ◽  
Luiz Carlos Reis ◽  
Teresinha Esteves da Silveira Reis
Keyword(s):  
Ground Surface ◽  
Digital Terrain Model ◽  
Large Area ◽  
Terrain Model ◽  
Spatial Point ◽  
Aster Gdem ◽  
Digital Terrain ◽  
Contour Lines ◽  
High Resolution Images ◽  
Point Data

The slope of terrain represents a risk factor for mechanized harvesting, leading to impediments or restrictions on agricultural operations, or even to machines toppling over in the field. Recently, the Digital Terrain Model (DTM) has become widely adopted as one of the most viable techniques for obtaining slope and elevation. Therefore, this study aims to assess methods of acquiring DTMs to calculate the slope, and to determine the areas that are suitable and unsuitable for the operation of harvesters in the municipality of Bandeirantes (PR). Four methods were selected to produce DTMs for the construction of slope zoning maps applicable for harvester operations. The image sources included SRTM, ASTER GDEM, digitizing contour lines and kriging of spatial point data. After generating DTMs by the four different methods, the area suitable for the operation of harvesters was obtained based on the limits of operational slopes for harvesters in the literature. The high-resolution images, such as those obtained by scanning the contour lines and ASTER GDEM gave the best representation of the ground surface. Regardless of the method used to obtain the operational slopes, the municipality has a large area that is suitable for mechanized harvesting.

scholarly journals PLANNING HARVESTING OPERATIONS IN FOREST ENVIRONMENT: REMOTE SENSING FOR DECISION SUPPORT

2019 ◽  
Vol IV-3/W1 ◽  
pp. 33-40
Author(s):  
M. Piragnolo ◽  
S. Grigolato ◽  
F. Pirotti
Keyword(s):  
Remote Sensing ◽  
Laser Scanner ◽  
Ground Surface ◽  
Digital Terrain Model ◽  
Remote Sensing Data ◽  
Forest Environment ◽  
K Value ◽  
Terrain Model ◽  
Digital Terrain ◽  
Roughness Index

<p><strong>Abstract.</strong> The goal of this work is to assess a method for supporting decisions regarding identification of most suitable areas for two types of harvesting approaches in forestry: skyline vs. forwarder. The innovative aspect consists in simulating the choices done during the planning in forestry operations. To do so, remote sensing data from an aerial laser scanner were used to create a digital terrain model (DTM) of ground surface under vegetation cover. Features extracted from the DTM are used as input for several machine learning predictors. Features are slope, distance from nearest roadside, relative height from nearest roadside and roughness index. Training and validation is done using areas defined by experts in the study area. Results show a K value of almost 0.92 for the classifier with best results, random forest. Sensibility of each feature is assessed, showing that both distance and height difference from nearest road-side are more significant than overall DTM value.</p>

scholarly journals Complex Analysis of the Impact of Construction of an Underground Metro Line on the Urban Environment – a Case Study from the Vistula Valley in Warsaw

2016 ◽  
Author(s):  
Łukasz Kaczmarek
Keyword(s):  
Urban Areas ◽  
Complex Analysis ◽  
Surface Deformation ◽  
Digital Terrain Model ◽  
Terrain Model ◽  
Digital Terrain ◽  
Vertical Displacements ◽  
The Stability ◽  
The Impact

Underground construction in urban areas is a complex investment, impacting existing buildings. The paper presents a case study of the 2nd metro line, in close proximity to the Warsaw Slope (Kaczmarek, Popielski 2016; Kaczmarek et al. 2016). First the digital terrain model was analysed. Next the prospection of electrical resistivity imaging (ERI) were performed. In addition results of archive boreholes were correlated to ERI outcome. Then complementary laboratory tests (e. g. triaxal CU tests) were carried out. Furthermore the prisms located on the Warsaw Slope were measured with tacheometric technique. This results were merged to archive monitoring observations of slope surface deformation and near building settlements. Based on previous steps the finite element method (FEM) simulations were performed. Thanks to numerical analysis cumulative settlements of a particular building above the metro tunnel were calculated. The values of vertical displacements does not affect the stability of the building or the slope nearby. Nevertheless, it can impact serviceability. Furthermore, the value of the calculated Safety Factor of the Warsaw Slope in this section is 1.1. Hence, slope changes require continuous observations. The presented case study shows the usefulness of complex research analysis and its suitability for the purposes of building an extension of the 2nd metro line.

scholarly journals A New Simplified DSM-to-DTM Algorithm – dsm-to-dtm-step

2018 ◽  
Author(s):  
Thomas Krauß
Keyword(s):  
Opposite Direction ◽  
Ground Surface ◽  
Digital Terrain Model ◽  
Ground Level ◽  
Test Area ◽  
Surface Model ◽  
Digital Surface Model ◽  
Simplified Approach ◽  
Terrain Model ◽  
Digital Terrain

In this paper we will present a simplified approach for extracting the ground level &ndash; a digital terrain model (DTM) &ndash; from the surface provided in a digital surface model (DSM). Most existing algorithms try to find the ground values in a digital surface model. Our approach works the opposite direction by detecting probable above ground areas. The main advantage of our approach is the possibility to use it with incomplete DSMs containing much no data values which can be e.g. occlusions in the calculated DSM. A smoothing or filling of such original derived DSMs will destroy much information which is very useful for deriving a ground surface from the DSM. Since the presented approach needs steep edges to detect potential high objects it will fail on smoothed and filled DSMs. After presenting the algorithm it will be applied to a test area in Salzburg and compared to a terrain model freely available from the Austrian government.

scholarly journals ASSESSMENT OF THE VULNERABILITY DEGREE OF DIFFERENT LITHOLOGICAL FORMATIONS IN THE CATCHMENT AREA OF AGIA EIRINI GORGE, WESTERN CRETE

2017 ◽  
Vol 43 (3) ◽  
pp. 1314
Author(s):  
A. Bizoura ◽  
E. Lykoudi ◽  
E. Spyridonos ◽  
E. Manoutsoglou
Keyword(s):  
Land Use ◽  
Spatial Data ◽  
Drainage Basin ◽  
Digital Terrain Model ◽  
Secondary Data ◽  
Thematic Maps ◽  
Management Planning ◽  
Terrain Model ◽  
Digital Terrain ◽  
The Impact

This paper presents a methodology for assessing the degree of vulnerability of different lithology formations constituting the drainage basin of the gorge of Agia Eirini. The methodology is based on the processing of spatial aspects parameters of lithology, hydrography, geomorphology and the vegetation cover, which are related with the weathering impact on formations either directly or indirectly. Initially a series of primary spatial data on geology, topography, the river network and the land use in the region, were used to produce thematic maps. These maps include the geological map, the digital terrain model (DTM), the map of the land use, and hydrographic maps of density and frequency. By processing the data according to their role in enhancing the vulnerability of formations, the data were determined and the following thematic maps: “Map of geological formations susceptible to weathering”, “Map of hydrographic texture”, “Map of morphological inclinations” and “land use map protecting against the loss of disintegrated material were produced. By appropriate combination of these secondary data, areas of vulnerability of formations were recorded which are shown on a final thematic map. This information is particularly valuable in the management planning and gives the opportunity to evaluate and predict the impact of various proposed projects or future scenarios. They can also be used to identify positions to take necessary measures to protect areas at high risk of loss of material.

scholarly journals Preliminary Archeological Site Survey by UAV-Borne Lidar: A Case Study

2021 ◽  
Vol 13 (3) ◽  
pp. 332
Author(s):  
Marco Balsi ◽  
Salvatore Esposito ◽  
Paolo Fallavollita ◽  
Maria Grazia Melis ◽  
Marco Milanese
Keyword(s):  
Ground Surface ◽  
Digital Terrain Model ◽  
Landscape Archaeology ◽  
Archaeological Site ◽  
Diagnostic Techniques ◽  
Terrain Model ◽  
Digital Terrain ◽  
Spatially Extended ◽  
Cloud Of Points

Preliminary analysis of an archaeological site requires the acquisition of information by several diverse diagnostic techniques. Remote sensing plays an important role especially in spatially extended and not easily accessible sites for the purposes of preventive and rescue archaeology, landscape archaeology, and intervention planning. In this paper, we present a case study of a detailed topographic survey based on a light detection and ranging (LiDAR) sensor carried by an unmanned aerial vehicle (UAV; also known as drone). The high-resolution digital terrain model, obtained from the cloud of points automatically labeled as ground, was searched exhaustively by an expert operator looking for entrances to prehistoric hypogea. The study documents the usefulness of such a technique to reveal anthropogenic structures hidden by vegetation and perform fast topographic documentation of the ground surface.

scholarly journals DTM-based analysis of the spatial distribution of topolineaments

2020 ◽  
Vol 12 (1) ◽  
pp. 1185-1199
Author(s):  
Mirosław Kamiński
Keyword(s):  
Laser Scanning ◽  
Digital Terrain Model ◽  
Research Area ◽  
Tectonic Structures ◽  
Empirical Bayesian ◽  
Scanning Method ◽  
Empirical Bayesian Kriging ◽  
Terrain Model ◽  
Digital Terrain ◽  
Airborne Laser

AbstractThe research area is located on the boundary between two Paleozoic structural units: the Radom–Kraśnik Block and the Mazovian–Lublin Basin in the southeastern Poland. The tectonic structures are separated by the Ursynów–Kazimierz Dolny fault zone. The digital terrain model obtained by the ALS (Airborne Laser Scanning) method was used. Classification and filtration of an elevation point cloud were performed. Then, from the elevation points representing only surfaces, a digital terrain model was generated. The model was used to visually interpret the course of topolineaments and their automatic extraction from DTM. Two topolineament systems, trending NE–SW and NW–SE, were interpreted. Using the kernel density algorithm, topolineament density models were generated. Using the Empirical Bayesian Kriging, a thickness model of quaternary deposits was generated. A relationship was observed between the course of topolineaments and the distribution and thickness of Quaternary formations. The topolineaments were compared with fault directions marked on tectonic maps of the Paleozoic and Mesozoic. Data validation showed consistency between topolineaments and tectonic faults. The obtained results are encouraging for further research.

scholarly journals Production, Validation and Morphometric Analysis of a Digital Terrain Model for Lake Trichonis Using Geospatial Technologies and Hydroacoustics

2021 ◽  
Vol 10 (2) ◽  
pp. 91
Author(s):  
Triantafyllia-Maria Perivolioti ◽  
Antonios Mouratidis ◽  
Dimitrios Terzopoulos ◽  
Panagiotis Kalaitzis ◽  
Dimitrios Ampatzidis ◽  
...  
Keyword(s):  
Morphometric Analysis ◽  
Ad Hoc ◽  
Regional Scale ◽  
Digital Terrain Model ◽  
Relevant Information ◽  
Relative Difference ◽  
Systematic Observation ◽  
Qualitative And Quantitative ◽  
Terrain Model ◽  
Digital Terrain

Covering an area of approximately 97 km2 and with a maximum depth of 58 m, Lake Trichonis is the largest and one of the deepest natural lakes in Greece. As such, it constitutes an important ecosystem and freshwater reserve at the regional scale, whose qualitative and quantitative properties ought to be monitored. Depth is a crucial parameter, as it is involved in both qualitative and quantitative monitoring aspects. Thus, the availability of a bathymetric model and a reliable DTM (Digital Terrain Model) of such an inland water body is imperative for almost any systematic observation scenario or ad hoc measurement endeavor. In this context, the purpose of this study is to produce a DTM from the only official cartographic source of relevant information available (dating back approximately 70 years) and evaluate its performance against new, independent, high-accuracy hydroacoustic recordings. The validation procedure involves the use of echosoundings coupled with GPS, and is followed by the production of a bathymetric model for the assessment of the discrepancies between the DTM and the measurements, along with the relevant morphometric analysis. Both the production and validation of the DTM are conducted in a GIS environment. The results indicate substantial discrepancies between the old DTM and contemporary acoustic data. A significant overall deviation of 3.39 ± 5.26 m in absolute bottom elevation differences and 0.00 ± 7.26 m in relative difference residuals (0.00 ± 2.11 m after 2nd polynomial model corrector surface fit) of the 2019 bathymetric dataset with respect to the ~1950 lake DTM and overall morphometry appear to be associated with a combination of tectonics, subsidence and karstic phenomena in the area. These observations could prove useful for the tectonics, geodynamics and seismicity with respect to the broader Corinth Rift region, as well as for environmental management and technical interventions in and around the lake. This dictates the necessity for new, extensive bathymetric measurements in order to produce an updated DTM of Lake Trichonis, reflecting current conditions and tailored to contemporary accuracy standards and state-of-the-art research in various disciplines in and around the lake.

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