Construction Of Digital Elevation Models Research Articles

Airborne Bathymetric Light Detection and Ranging Waveform Processing for Digital Elevation Model Construction of Tidal Flats on the West Coast of Korea

Airborne Bathymetric Light Detection and Ranging Waveform Processing for Digital Elevation Model Construction of Tidal Flats on the West Coast of Korea

Construction of high-precision DEMs for urban plots

ABSTRACT High-precision digital elevation models (DEMs) are the basic data for constructing digital cities. With the acceleration of urbanization, the topography of urban plots is constantly transformed by human activities, so that surface morphology shows the characteristics of diversification and discontinuity. Existing modelling methods focus on the expression of continuous terrain. Constructing high-precision DEM in urban plots is still challenging. A block-based modelling method that considers the morphological characteristics of urban plot elements was proposed. The Jinzhai County urban area was selected as the research area. The elements of urban plots were classified into six types, in which the boundaries and elevation information were extracted with real sense 3D models, Digital Orthophoto Maps (DOMs) and dense matching point cloud data. The DEMs of the 6 types of elements were generated separately with different methods, that are fused to complete the DEM of urban plots. The DEM obtained using the method in this manuscript was consistent with the reality in terms of topographic relief within each element and clarified the boundary of each element. The accuracy assessment showed that the RMSE results of roads, slopes, other terrains and natural terrains are approximately 0.05 m, which meets the elevation accuracy requirements of the 1:1000 large-scale mapping.

Integrating topographic knowledge into point cloud simplification for terrain modelling

Terrain models are widely used to depict the shape of the Earth’s surface. With the development of photogrammetric methods, point cloud data have become one of the most popular data sources for terrain modelling. However, the obtained point clouds are of high density, which often increases redundancy rather than improving accuracy. Therefore, point cloud simplification should be a core component of terrain modelling. This paper proposes a point cloud simplification method by integrating topographic knowledge into terrain modelling (TKPCS). The method contains two steps: (1) topographic knowledge recognition and construction and (2) point cloud simplification using this topographic knowledge for terrain modelling. The proposed approach is benchmarked against improved versions of existing methods to validate its capability and accuracy in digital elevation model construction and terrain derivative extraction. The results show that the simplified points of the TKPCS method can generate finer resolution terrain models with higher accuracy and greater information entropy. The good performance of the TKPCS method is also stable at different scales. This work endeavours to transform perceptive topographic knowledge into a process of point cloud simplification and can benefit future research related to terrain modelling.

K-span: Open and reproducible spatial analytics using scientific workflows

This paper describes the design, development, and testing of a general-purpose scientific-workflows tool for spatial analytics. Spatial analytics processes are frequently complex, both conceptually and computationally. Adaptation, documention, and reproduction of bespoke spatial analytics procedures represents a growing challenge today, particularly in this era of big spatial data. Scientific workflow systems hold the promise of increased openness and transparency with improved automation of spatial analytics processes. In this work, we built and implemented a KNIME spatial analytics (“K-span”) software tool, an extension to the general-purpose open-source KNIME scientific workflow platform. The tool augments KNIME with new spatial analytics nodes by linking to and integrating a range of existing open-source spatial software and libraries. The implementation of the K-span system is demonstrated and evaluated with a case study associated with the original process of construction of the Australian national DEM (Digital Elevation Model) in the Greater Brisbane area of Queensland, Australia by Geoscience Australia (GA). The outcomes of translating example spatial analytics process into a an open, transparent, documented, automated, and reproducible scientific workflow highlights the benefits of using our system and our general approach. These benefits may help in increasing users’ assurance and confidence in spatial data products and in understanding of the provenance of foundational spatial data sets across diverse uses and user groups.

Диагностирование и определение аномальных зон магистральных трубопроводов на подводных переходах с использованием цифровой модели рельефа

The article considers the issues of geodetic support for monitoring the technical condition of main gas pipelines underwater crossings (MGPUC). The purpose of the research is to increase the accuracy of determining the depth of the gas pipeline underwater crossings of main gas pipelines by taking into account the zones of faulty location of the pipeline (anomalous zones) and the bottom surface above MGPUC. The main problem of determining the technical condition of the gas pipeline underwater crossing is the difficulty of determining the depth of the gas pipeline due to the influence of external factors (soil, constructions and communications) on the measuring equipment (underwater trace detectors). The study indicates the accuracy of building digital elevation models (DEM) of the bottom, from which the calculation of the protective roll over the gas pipeline, which affects the determination of the technical state, and the causes of anomalous zones, as well as the ways of their determination. The variants of increasing the accuracy of calculating the depths of the gas pipeline location taking into account the DEM data are studied. The approach to definition of the method of spatial interpolation for construction of the bottom DEM according to the echolocation data depending on the surface curvature changes is offered. The authors note the interrelation of determining the criterion of technical condition of under-water crossing with the accuracy of DEM construction and determination of the spatial position of the pipeline. The proposed approaches are aimed at reducing the influence of the systematic part of the error and increasing the accuracy of the depth of occurrence, which is an urgent task.

Multi-information PointNet++ fusion method for DEM construction from airborne LiDAR data

Airborne light detection and ranging (LiDAR) is a popular technology in remote sensing that can significantly improve the efficiency of digital elevation model (DEM) construction. However, it is challenging to identify the real terrain features in complex areas using LiDAR data. To solve this problem, this work proposes a multi-information fusion method based on PointNet++ to improve the accuracy of DEM construction. The RGB data and normalized coordinate information of the point cloud was added to increase the number of channels on the input side of the PointNet++ neural network, which can improve the accuracy of the classification during feature extraction. Low and high density point clouds obtained from the International Society for Photogrammetry and Remote Sensing (ISPRS) and the United States Geological Survey (USGS) were used to test this proposed method. The results suggest that the proposed method improves the Kappa coefficient by 8.81% compared to PointNet++. The type I error was reduced by 2.13%, the type II error was reduced by 8.29%, and the total error was reduced by 2.52% compared to the conventional algorithm. Therefore, it is possible to conclude that the proposed method can obtain DEMs with higher accuracy.

ГЕОДЕЗІЯ, КАРТОГРАФІЯ І АЕРОФОТОЗНІМАННЯ

The purpose of the work is to investigate the digital elevation models of the mass grave of 1944, built on the basis of aerial and cartographic data of different times. The implementation of the task involves the construction of digital elevation models (DEM) on the territory of the Jewish mass grave in the city of Vynnyky and Italian prisoners of war near the city. On the territory of the Jewish mass grave in the city of Vynnyky, a DEM was created based on a stereo pair of archival aerial images obtained in 1944 and on the basis of aerial photography from a UAV conducted in 2015. Since archival aerial photographs did not contain orientation elements, they were geometrically transformed using the ErdasImagine software. After that, the stereo pair was processed in the program Digitals, where relief elements on the territory of the mass grave were obtained. Aerial photography from a UAV on the territory of the city of Vynnyky provided the data which was processed in the Agisoft PhotoScan software. It allowed us to create an orthophoto plan and an elevation map of the city territory. Elements of relief on the territory of the mass grave of 1944 and 2015 were imported into the Surfer software environment, where 3D digital elevation models were built. Since the territory of the grave did not have significant differences in height, and the relief was quite gentle, the method of constructing the DEM of the Natural Neighbor was chosen, which gave a positive result. Analyzing the digital elevation model and the vector map for 1944, the border of the mass grave is clearly distinguished, since the height difference between its edges and the rest of the territory is from 20 to 36 cm, depending on the section of the border. The analysis of the digital elevation models and the vector map for 2015 of the territory of the mass grave determined from the aerial image of 1944 showed that the characteristic height differences on the former border of the grave are observed only in the left-right corner of the grave and on a separate section of the right border. Height difference indicators range from 15 to 20 cm. It should be noted that height differences are also observed in the rest of the territory belonging to the mass grave and outside it. This can be explained by many years of human intervention and agricultural land use. With regard to the investigation of the mass graves of Italian prisoners of war near the city of Vynnyky, the modern territory is 100% wooded, which makes it impossible to apply aerial photography. Therefore, in order to compare the modern DEM with the stereo pair of aerial images of 1944, it was decided to conduct a ground tacheometric survey of the area in 2011. Tacheometric survey data was exported to the dxf exchange format, after which it was opened in Surfer and the DEM was built. In this case, digital elevation models were built using the Kriging method, since the area where the mass graves are located is quite hilly with a significant difference in elevation. According to the digital elevation models, 54 pits with burials that have survived to this day have been identified. The scientific novelty of the work consists in the development of the concept of combining disparate data for the construction of digital elevation models and the creation of a complete picture of the study of the territory of the object of historical and cultural heritage. The received data can be used by the relevant cultural heritage preservation departments of the Ministry of Culture of Ukraine for their further study.

Adaptive digital elevation models construction method based on nonparametric regression

AbstractInterpolation is one of the most critical factors affecting the quality of digital elevation models (DEM) generated from sampling point data. However, existing methods have not taken into full account that the interpolation function should be consistent with the density and direction characteristics of sampling points. Therefore, an adaptive DEM construction method based on nonparametric regression (AdpNPR‐DEM) is proposed, which incorporates an adaptive kernel that changes according to local landform types. The method first estimates local terrain features, and second the dominant orientation of the local gradients. The orientation information adaptively “steers” the local kernel to produce elongated, elliptical contours that spread along the directions of local terrain features. The effectiveness of the AdpNPR‐DEM is verified based on directional features, the number of sampling points, and typical landform types. The results show that, compared with triangulated irregular network (TIN), natural neighbor interpolation (NNI), and the Australian National University digital elevation model (ANUDEM) interpolation method, AdpNPR‐DEM has the highest accuracy for all landform types and a better level of robustness. Our method improves the quality of DEM in areas with complex landforms. It could significantly promote the high‐quality production of DEMs, and also promisingly broaden and deepen its applications.

Application of Airborne LiDAR Measurements to the Topographic Survey of the Tidal Flats of the Northern Jiangsu Radial Sand Ridges in the Southern Yellow Sea

The northern Jiangsu radial sand ridges are typical geomorphic deposit units distributed off the Jiangsu coast. A coastal tidal flat typically develops and provides a good habitat for many migratory birds and benthic organisms. However, topographic surveys of tidal flats have always been difficult in marine surveys because of the dense tidal creek, poor accessibility, and difficulty in setting up control points. In this study, we quickly obtained the point cloud data of the tidal flat near Yangkou Port in the southern part of the radial sand ridges based on an airborne LiDAR system, an integrated 3D laser scanner and a positioning and attitude determination system. We analyzed the adaptabilities of multiple filtering algorithms to tidal flats. In addition, a digital elevation model (DEM) of the tidal flat was constructed and the accuracy was verified with synchronized beach GPS-RTK topographic elevation measurements. The results show that the following: (1) Airborne LiDAR can quickly obtain high precision, high resolution, and a large area of ground point cloud information for tidal flats, overcoming the shortcomings of traditional measurement methods. (2) The triangulated irregular network (TIN) filtering effect is better than that of mathematical morphology and the filtering effect of point cloud normal vector clustering is mediocre. (3) The DEM of the LiDAR point cloud is in good agreement with RTK and the average error of the measurement results is 0.108 m. The error accuracy of the DEM satisfies the surveying specification of a 1:500 topographic map in a flat area, which proves that the airborne LiDAR system can be suitable for tidal flat elevation measurement. Nevertheless, it is possible to provide high precision terrain detection and DEM construction of a tidal flat with the development of airborne infrared and blue-green laser detection radar.

Satellite-Derived Topography and Morphological Evolution around Authie Macrotidal Estuary (France)

The wide spatial and temporal coverage of remotely sensing images is an essential asset to analyze the morphological behaviour of fast-changing coastal environments such as estuarine systems. This paper investigates the reliability of intertidal topography mapping around the Authie Bay, a macrotidal estuarine system located on the northern coast of France. A Satellite-Derived Topography technique is developed by relating the green band reflectance of Sentinel-2 images to rapid variations in topography. This method is well suited to small sedimentary structures of the coastal zone with a 0.30 to 0.35 m height accuracy of the constructed Digital Elevation Model (DEM). For the more complex estuarine configuration, the waterline method was applied and resulted in the construction of DEMs with a height accuracy of 0.35 to 0.38 m. Video animations and records of Authie meander positions along transects are created from Sentinel-2 and Landsat satellite archives (1984–2020). These materials allow to highlight a sedimentation phase at the east side of the spit since 2015. It constrains the main channel towards the eastern bank, thus promoting coastal erosion. The monitoring of a severe erosion phase throughout 2019 shows a 130 m retreat of the coastline. Topographic map differentiation led to the detection of a sedimentation anomaly upstream of the bay, probably linked to this erosion event.

Applicability of Data Acquisition Characteristics to the Identification of Local Artefacts in Global Digital Elevation Models: Comparison of the Copernicus and TanDEM-X DEMs

Several global digital elevation models (DEMs) have been developed in the last two decades. The most recent addition to the family of global DEMs is the TanDEM-X DEM. The original version of the TanDEM-X DEM is, however, a nonedited product (i.e., it contains local artefacts such as voids, spikes, and holes). Therefore, subsequent identification of local artefacts and their editing is necessary. In this study, we evaluated the accuracy of the original TanDEM-X DEM and its improved edited version, the Copernicus DEM, in three major European mountain ranges (the Alps, the Carpathians, and the Pyrenees) using a digital surface model derived from airborne laser scanning data as a reference. In addition, to evaluate the applicability of data acquisition characteristics (coverage map, consistency mask, and height error map) and terrain characteristics (slope, aspect, altitude) to the localization of problematic sites, we modeled their associations with the TanDEM-X DEM error. We revealed local occurrences of large errors in the TanDEM-X DEM that were typically found on steep ridges or in canyons, which were largely corrected in the Copernicus DEM. The editing procedure used for the Copernicus DEM construction was evidently successful as the RMSE for the TanDEM-X and Copernicus DEMs at the 90 m resolution improved from 45 m to 12 m, from 16 m to 6 m, and from 24 m to 9 m for the Alps, the Pyrenees, and the Carpathians, respectively. The Copernicus DEM at the 30 m resolution performed similarly well. The boosted regression trees showed that acquisition characteristics provided as auxiliary data are useful for locating problematic sites and explained 28–50% of deviance of the absolute vertical error. The absolute vertical error was strongly related to the height error map. Finally, up to 26% of cells in the Copernicus DEM were filled using DEMs from different time periods and, hence, users performing multitemporal analysis or requiring data from a specific time period in the mountain environment should be wary when using TanDEM-X and its derivations. We suggest that when filling problematic sites using alternative DEMs, more attention should be paid to the period of their collection to minimize the temporal displacement in the final products.

On the topographic entity-oriented digital elevation model construction method for urban area land surface

Human activity transforms a land surface into a complex surface where artificial and natural landforms coexist and continuous and emergent landforms merge. In this background, the problems of conventional digital elevation models (DEMs), such as morphological distortion, complicated updates, and lack of information, are increasingly prominent. This study proposes a new idea of DEM construction based on the concept of geographic ontology. First, landforms with common features are abstracted into a certain type of topographic entity based on their morphologies and semantics. For each type of topographic entity, a DEM was constructed independently based on the available elevation information and other information about the semantics and spatial relationships. Second, individual DEMs were merged into a complete DEM following certain rules. A 1 km2 area located in the suburb of Nanjing, Jiangsu Province, China, was selected as the experimental area. The effectiveness of the model construction method proposed in this study was verified. The results show that the DEM constructed according to the idea of this study has a significantly better performance than the conventional DEMs. The constructed DEM in this study can well represent ground objects, such as slopes, farmland, and ditches. In particular, the constructed DEM ensures the morphological accuracy of the ground objects.

Impact of data sources to DEM construction and application to runoff and sediment yield modelling using LISEM model

The use of interpolated digital elevation models (DEM) obtained from free low-resolution satellite images is a typical solution for soil erosion modelling. However, this method may result in loss of surface details, especially in small catchments. Thus, planialtimetric surveys at the study site may improve quality of terrain description, although it requires high costs and time. Therefore, this study aims to evaluate the impact of two DEM sources on the results of a process-based erosion model. The study was developed in the Lajeado Ferreira creek catchment (1.23 km2) in southern Brazil. Two interpolated 5-m resolution DEM maps obtained from: (i) remote sensing source Shuttle Radar Topography Mission (SRTM), and (ii) field topographic survey with Global Navigation Satellite System using Real Time Kinematic (GNSS/RTK); were used as input in the Limburg Soil Erosion Model (LISEM) to simulate runoff and sediment transport. Two other maps required for modelling were developed from each DEM source: the flow direction and drainage network map. Six monitored rainfall events were calibrated for the variables, timing of peak flow (Qtime), peak flow (Qpeak), surface runoff coefficient (C), total surface runoff volume (Qtotal) and sediment yield (SY). Most variables calibrated were within the acceptable statistical ranges. The Qtime and Qpeak simulated for all events were close to the measured values with minor modification of the input parameters while using GNSS/RTK. However, even in maps with better accuracy of relief description (GNSS/RTK), the erosion parameters adjusted for calibration were not within an acceptable physical limit. For example, soil cohesion values had to be multiplied for at least eight times their original value. Hydrograph and sedimentgraph shapes calibration did not reach a satisfactory statistical level, even with the GNSS/RTK database and the incorporation of relevant features of the landscape based on local observation. Although GNSS/RTK database resulted in gains for some variables calibrated with the LISEM model, the advantages were not significant for the conditions of this study.

Creating a digital relief model by aerial photography materials in Civil 3D software

Research of certain aspects of using a digital elevation model (DEM), their classification and methods of obtaining in the Civil 3D software is presented in this article. A land plot with vegetation and the building of the educational building of the NULES of Ukraine was used as an object for the study. The analysis of aerial photography materials of the territory of the research object is carried out. A digital point cloud was created, which was taken as a basis for the further construction of digital elevation models. Сlassification of surfaces in the Civil 3D software is offered in article. An algorithm for the formation of plane components and data filling is considered. Highlighted the problems that arise in a robot with a cloud of points and surface formation using Autodesk ReCap and Civil 3D. The main advantages and disadvantages of building a relief on the basis of point clouds formed on the basis of aerial photography of the terrain are shown. Attention is focused on the main ways to reduce the identified shortcomings. The functionality and capabilities of Civil 3D and Autodesk ReCap software, as well as the features of constructing surfaces based on different initial data, are considered. The comparison of the DEM (generated using the Autodesk Civil 3D software) and the topographic plan (generated as a result of tacheometric survey) is given.

Urban road DEM construction based on geometric and semantic characteristics

The accurate expression of terrain morphology is the essence of the urban terrain model construction. As the skeleton of urban terrain, urban road has special geometric and semantic characteristics. The road is a strip-shaped feature, which is flat in the horizontal direction and gently undulating in the vertical direction, and the roads are interlinked and connected. This research takes Jianye District of Nanjing as the studied area to explore the digital elevation model (DEM) construction method of urban roads. Firstly, the 1:1000 digital topographic map(DTM) is used to extract the point, line and plane elements of urban roads. Secondly, a selection method of elevation points for urban road DEM (UR-DEM) construction is proposed, referring to the urban road engineering design specification. That’s the improved Douglas–Peucker (D–P) algorithm with elevation change rate. Thirdly, the bidirectional interpolation method is constructed to keep the directional characteristics and geometric features of the urban roads. Then, the intersection processing method based on semantic connectivity is used, so that the roads can be connected correctly. Finally, UR-DEM is generated by inverse distance weighting (IDW) interpolation model, and the construction results are also analyzed and evaluated in this paper. The experimental results show that: (1) the existence of abnormal elevation points seriously affects the geometric shape of urban road, and the removing abnormal elevation points method proposed in this paper can maintain gently undulating characteristics of road well and largely reduce the road jitter. (2) The UR-DEM construction method proposed in this paper can express the spatial geometric and semantic features of urban road well, the model accuracy is higher than that of classical methods and the RMSE is 0.0225 m. This study can provide reference for the DEM construction of other urban features, and can provide data support for the process simulation of urban surface confluence and urban construction planning.

An indirect interpolation model and its application for digital elevation model generation

Spatial interpolation is an important facet of generating digital elevation models (DEMs). When faced with geographical big data, a DEM with high accuracy is required in many types of investigations and applications. This requirement has encouraged researchers to enhance current interpolation methods and improve DEM construction as much as possible. Currently, almost all spatial interpolation methods use given sampling points as inputs and then calculate the missing sampling points individually. All of them consider terrain similarities in local areas but fail to consider the influence of the varying tendency in the overall terrain. In this paper, we propose a new concept for spatial interpolation that also considers local terrain similarity. However, in our approach, the unknown elevation points are expressed using both sampling points and unknown neighboring elevation points. In this way, the unknown elevation points of the entire computed region are connected formulaically, which introduces the trend features of terrain changes into the DEM construction process. We select a typical experimental area and conduct a DEM experiment based on elevation data sources. The experiment reveals that compared with traditional methods, the new method constructs a more accurate DEM, with morphological characteristics that are more consistent with the real terrain surface.

DEM Construction Method for Slopes Using Three-Dimensional Point Cloud Data Based on Moving Least Square Theory

AbstractThe multitemporal digital elevation model (DEM) of slopes constructed from three-dimensional (3D) point cloud data (PCD), which is obtained by terrestrial laser scanning (TLS), can realize ...

Comparison of Different DEM Generation Methods based on Open Source Datasets

Digital Elevation Model (DEM) is one of the developed techniques for relief representation. The definition of a DEM construction is the modeling technique of earth surface from existing data. DEM plays a role as one of the fundamental information requirement that has been generally utilized in GIS data structures. The main aim of this research is to present a methodology for assessing DEMs generation methods. The DEMs data will be extracted from open source data e.g. Google Earth. The tested data will be compared with data produced from formal institutions such as General Directorate of Surveying. The study area has been chosen in south of Iraq (Al-Gharraf / Dhi Qar governorate. The methods of DEMs creation are kriging, IDW (inverse distance weight), spline, and natural neighbor. This research used different software for processing and analysis such as ArcGIS 10.2, TCX and Civil 3D. Two- sample t-test has been adopted to investigate the mean of elevation differences between compared datasets. The results showed that the spline is the best method that can be used to build DEM in this study area.

A feature-preserving point cloud denoising algorithm for LiDAR-derived DEM construction

To attenuate positional errors of LiDAR-derived datasets for constructing digital elevation models (DEMs), a feature-preserving point denoising algorithm (F-PDA) is developed in this paper. F-PDA includes three main steps: surface normal estimation, normal filtering and point position update. Numerical tests with two simulated surfaces indicate that F-PDA is always more accurate than kriging and natural neighbour. Furthermore, F-PDA has a high effectiveness of preserving feature lines. Real-world examples of interpolating LiDAR samples demonstrate that F-PDA can best retain both prominent and subtle terrain features, while faithfully removing errors in mountainous and flat regions. Moreover, it outperforms some well-known interpolation methods.

Creation of the digital elevation model with the use of unmanned aerial vehicle

The necessary sequence of stages has been developed and the unmanned technology for creating a digital elevation model by the example of the land use of Novosibirsk region has been implemented. The technology consists of a set of stages: reconnaissance of the terrain, fi xing reference signs, satellite measurements, aerial photography fl ights, processing the results of aerial photography and the construction of digital elevation model. The technological process was signifi cantly affected by unfavorable weather conditions - low clouds, gusty wind, high air humidity. Remote sensing study with the use of unmanned aerial vehicle of the Supercam S 250 F type made it possible to create a large-scale orthophotoplan and a digital elevation model on the farm territory (M 1 : 1000). For photogrammetric processing of digital data obtained on the farm, a two-stage method of satellite determination was used. The essence of this method was to obtain a large number of satellite measurements in a static mode and further statistical processing. For statistical processing of satellite measurements, information was used on the coordinate location of two base ground stations of the Novosibirsk Region satellite network - Kochenevo and Novosibirsk. Remoteness of support points from the ground satellite station of Novosibirsk was at a distance of over 90 km. As a result of equalization calculations, the obtained average square displacement errors of the planned and high-altitude position of the support points in various test sites were under 0.02 m in the plan, and under 0.03 m by height. In the process of photogrammetric processing of the results of aerial photography with the use of unmanned aerial vehicle, the tasks of transferring the position of points on a digital image in the pixel coordinate system into the coordinate system of the area, building digital irregular (TIN, Triangulated Irregular Network) and regular (DEM, Digital Elevation Model) surface models, and based on them, textured terrain models (TTM, Textured Terrain Model) and orthophotoplans, were solved.