Visualizations of the Doblar Accumulation Basin Based on the UAV Survey

Abstract. Our research is based on a large case study of Unmanned Aerial Vehicle (UAV) surveys, modelling and visualizations of the Doblar accumulation basin. The various approaches for UAV surveying of large, demanding terrain configurations, and the benefits of surveying products used as a basis for other interdisciplinary hydrological and environmental services were researched. The demanding mountainous terrain, the steep slopes and deep and narrow streams required detailed pre-planning of the survey, including the pre-survey terrain overview. The accumulation basin was emptied merely for a short period; thus, the survey was performed in unfavourable weather conditions, which included coldness, snowfall and wind. Point clouds were generated and georeferenced from the 4377 recorded photos. The dense point cloud contained approximately 222 million points in the medium setting and more than a billion in the high setting. A 3D model was built from the data. This became the basis for numerous further analyses and for the presentation using cartographic principles: a digital elevation model with a resolution of 10&thinsp;cm, an orthophoto with a resolution of 10&thinsp;cm, a 3D model draped with orthophoto, contour lines with a 1&thinsp;m interval, topographic profiles, calculations of volumes at different water levels, a flythrough, augmented reality and a video simulation of the water level changes. The model can also serve as a basis for hydraulic and environmental analysis and simulations or used for analyses of the accumulation and deposition of river material compared with previous and future surveys.

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PERFORMANCE EVALUATION OF DIFFERENT GROUND FILTERING ALGORITHMS FOR UAV-BASED POINT CLOUDS

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xli-b1-245-2016 ◽

2016 ◽

Vol XLI-B1 ◽

pp. 245-251 ◽

Cited By ~ 9

Author(s):

C. Serifoglu ◽

O. Gungor ◽

V. Yilmaz

Keyword(s):

Point Cloud ◽

Point Clouds ◽

Good Alternative ◽

Lidar Data ◽

Filtering Algorithms ◽

Aerial Photos ◽

Digital Elevation ◽

Aerial Vehicle ◽

Elevation Model ◽

Uav Images

Digital Elevation Model (DEM) generation is one of the leading application areas in geomatics. Since a DEM represents the bare earth surface, the very first step of generating a DEM is to separate the ground and non-ground points, which is called ground filtering. Once the point cloud is filtered, the ground points are interpolated to generate the DEM. LiDAR (Light Detection and Ranging) point clouds have been used in many applications thanks to their success in representing the objects they belong to. Hence, in the literature, various ground filtering algorithms have been reported to filter the LiDAR data. Since the LiDAR data acquisition is still a costly process, using point clouds generated from the UAV images to produce DEMs is a reasonable alternative. In this study, point clouds with three different densities were generated from the aerial photos taken from a UAV (Unmanned Aerial Vehicle) to examine the effect of point density on filtering performance. The point clouds were then filtered by means of five different ground filtering algorithms as Progressive Morphological 1D (PM1D), Progressive Morphological 2D (PM2D), Maximum Local Slope (MLS), Elevation Threshold with Expand Window (ETEW) and Adaptive TIN (ATIN). The filtering performance of each algorithm was investigated qualitatively and quantitatively. The results indicated that the ATIN and PM2D algorithms showed the best overall ground filtering performances. The MLS and ETEW algorithms were found as the least successful ones. It was concluded that the point clouds generated from the UAVs can be a good alternative for LiDAR data.

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Combination of UAV and terrestrial photogrammetry to assess rapid glacier evolution and map glacier hazards

Natural Hazards and Earth System Science ◽

10.5194/nhess-18-1055-2018 ◽

2018 ◽

Vol 18 (4) ◽

pp. 1055-1071 ◽

Cited By ~ 24

Author(s):

Davide Fugazza ◽

Marco Scaioni ◽

Manuel Corti ◽

Carlo D'Agata ◽

Roberto Sergio Azzoni ◽

...

Keyword(s):

Laser Scanning ◽

Point Clouds ◽

Data Sets ◽

Survey Techniques ◽

Digital Elevation ◽

Standard Tool ◽

Aerial Vehicle ◽

Close Range ◽

Elevation Model ◽

Thinning Rate

Abstract. Tourists and hikers visiting glaciers all year round face hazards such as sudden terminus collapses, typical of such a dynamically evolving environment. In this study, we analyzed the potential of different survey techniques to analyze hazards of the Forni Glacier, an important geosite located in Stelvio Park (Italian Alps). We carried out surveys in the 2016 ablation season and compared point clouds generated from an unmanned aerial vehicle (UAV) survey, close-range photogrammetry and terrestrial laser scanning (TLS). To investigate the evolution of glacier hazards and evaluate the glacier thinning rate, we also used UAV data collected in 2014 and a digital elevation model (DEM) created from an aerial photogrammetric survey of 2007. We found that the integration between terrestrial and UAV photogrammetry is ideal for mapping hazards related to the glacier collapse, while TLS is affected by occlusions and is logistically complex in glacial terrain. Photogrammetric techniques can therefore replace TLS for glacier studies and UAV-based DEMs hold potential for becoming a standard tool in the investigation of glacier thickness changes. Based on our data sets, an increase in the size of collapses was found over the study period, and the glacier thinning rates went from 4.55 ± 0.24 m a−1 between 2007 and 2014 to 5.20 ± 1.11 m a−1 between 2014 and 2016.

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PERFORMANCE EVALUATION OF DIFFERENT GROUND FILTERING ALGORITHMS FOR UAV-BASED POINT CLOUDS

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xli-b1-245-2016 ◽

2016 ◽

Vol XLI-B1 ◽

pp. 245-251 ◽

Cited By ~ 1

Author(s):

C. Serifoglu ◽

O. Gungor ◽

V. Yilmaz

Keyword(s):

Point Cloud ◽

Point Clouds ◽

Good Alternative ◽

Lidar Data ◽

Filtering Algorithms ◽

Aerial Photos ◽

Digital Elevation ◽

Aerial Vehicle ◽

Elevation Model ◽

Uav Images

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Terrain-Based Shadow Correction Method for Assessing Supraglacial Features on the Greenland Ice Sheet

Frontiers in Remote Sensing ◽

10.3389/frsen.2021.690474 ◽

2021 ◽

Vol 2 ◽

Author(s):

Sasha. Z. Leidman ◽

Åsa K. Rennermalm ◽

Richard G. Lathrop ◽

Matthew. G. Cooper

Keyword(s):

Land Surface ◽

Greenland Ice Sheet ◽

Correction Method ◽

Correction Coefficient ◽

Digital Elevation ◽

Aerial Vehicle ◽

Sediment Cover ◽

Elevation Model ◽

Uav Images ◽

Gis Software

The presence of shadows in remotely sensed images can reduce the accuracy of land surface classifications. Commonly used methods for removing shadows often use multi-spectral image analysis techniques that perform poorly for dark objects, complex geometric models, or shaded relief methods that do not account for shadows cast on adjacent terrain. Here we present a new method of removing topographic shadows using readily available GIS software. The method corrects for cast shadows, reduces the amount of over-correction, and can be performed on imagery of any spectral resolution. We demonstrate this method using imagery collected with an uncrewed aerial vehicle (UAV) over a supraglacial stream catchment in southwest Greenland. The structure-from-motion digital elevation model showed highly variable topography resulting in substantial shadowing and variable reflectance values for similar surface types. The distribution of bare ice, sediment, and water within the catchment was determined using a supervised classification scheme applied to the corrected and original UAV images. The correction resulted in an insignificant change in overall classification accuracy, however, visual inspection showed that the corrected classification more closely followed the expected distribution of classes indicating that shadow correction can aid in identification of glaciological features hidden within shadowed regions. Shadow correction also caused a substantial decrease in the areal coverage of dark sediment. Sediment cover was highly dependent on the degree of shadow correction (k coefficient), yet, for a correction coefficient optimized to maximize shadow brightness without over-exposing illuminated surfaces, terrain correction resulted in a 49% decrease in the area covered by sediment and a 29% increase in the area covered by water. Shadow correction therefore reduces the overestimation of the dark surface coverage due to shadowing and is a useful tool for investigating supraglacial processes and land cover change over a wide variety of complex terrain.

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Rockfall Risk Analysis Based on Precise Topography using UAV

Korean Society of Hazard Mitigation ◽

10.9798/kosham.2020.20.4.63 ◽

2020 ◽

Vol 20 (4) ◽

pp. 63-73

Author(s):

Jaehee Choi ◽

Namgyun Kim ◽

Bongjin Choe ◽

Byonghee Jun

Keyword(s):

Point Cloud Data ◽

University Campus ◽

Digital Map ◽

Cloud Data ◽

The Road ◽

Mountainous Regions ◽

Digital Elevation ◽

Surface Models ◽

Aerial Vehicle ◽

Elevation Model

In this study, the risk of rockfall on incision slopes adjacent to roads was evaluated using the RocFall program. The study area was a slope adjacent to the road leading to a university campus in Samcheok-si, Gangwon-do, with an area of 774 m2 and an average slope of approximately 43°. A rock shed was installed at the lower zone of the slope. A 3D model of the terrain was generated based on point cloud data gathered using a UAV (unmanned aerial vehicle). Fast and accurate orthoimages were captured by UAV and high-resolution digital surface models (DSMs) were produced; these data were used to assess the risk of rockfall. Compared to terrain extraction using a digital elevation model (DEM) generated from an existing digital map, terrain extraction using a UAV was more effective in deriving results close to the actual situation in the field, especially for the analysis of rockfall jump height and kinetic energy. The necessity of constructing 3D topographic data using UAVs to predict rockfall disasters in mountainous regions was confirmed.

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CREATING DIGITAL ELEVATION MODEL USING A MOBILE DEVICE

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-iv-4-w4-203-2017 ◽

2017 ◽

Vol IV-4/W4 ◽

pp. 203-207 ◽

Cited By ~ 1

Author(s):

A. İ. Durmaz

Keyword(s):

Mobile Devices ◽

Digital Elevation Model ◽

Mobile Device ◽

Point Clouds ◽

Lidar Data ◽

Government Agencies ◽

Gps Data ◽

Digital Elevation ◽

The World ◽

Elevation Model

DEM (Digital Elevation Models) is the best way to interpret topography on the ground. In recent years, lidar technology allows to create more accurate elevation models. However, the problem is this technology is not common all over the world. Also if Lidar data are not provided by government agencies freely, people have to pay lots of money to reach these point clouds. In this article, we will discuss how we can create digital elevation model from less accurate mobile devices’ GPS data. Moreover, we will evaluate these data on the same mobile device which we collected data to reduce cost of this modeling.

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The UAS-Based 3D Image Characterization of Mozarabic Church Ruins in Bobastro (Malaga), Spain

Remote Sensing ◽

10.3390/rs12152377 ◽

2020 ◽

Vol 12 (15) ◽

pp. 2377

Author(s):

Carlos Enríquez ◽

Juan Manuel Jurado ◽

Alexandro Bailey ◽

Danilo Callén ◽

María José Collado ◽

...

Keyword(s):

3D Reconstruction ◽

Archaeological Site ◽

Semantic Classification ◽

Spatial Features ◽

Digital Elevation ◽

Dense Point ◽

Critical Slope ◽

Rgb Images ◽

Elevation Model

In recent years, the application of geomatics tools in archaeology has proved to be very useful to obtain meaningful knowledge of the 3D reconstruction of archaeological remains and semantic classification of the 3D surface. These techniques have proven to be an effective solution for the 3D modeling and the extraction of many spatial features on an archaeological site. However, novel methodologies as well as new data exploitation strategies are required to exploit these geospatial data for natural and cultural heritage documentation, monitoring, and preservation. In this paper, we have studied unique archaeological ruins, a Mozarab church in Al-Andalus, using high-resolution RGB images, which was taken by a drone. Thus, a 3D reconstruction of the ruins and the surrounding environment is carried out in order to characterize it on a dense point cloud. Then, a digital elevation model (DEM) was calculated in order to identify critical slope lines, which are significant to determine where the structure of the church was built. Our results can be used for the development of an architectural project and thus a virtual recreation of these archaeological ruins was performed.

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Spatial Analysis Using Temporal Point Clouds in Advanced GIS: Methods for Ground Elevation Extraction in Slant Areas and Building Classifications

ISPRS International Journal of Geo-Information ◽

10.3390/ijgi8030120 ◽

2019 ◽

Vol 8 (3) ◽

pp. 120 ◽

Cited By ~ 16

Author(s):

Sara Shirowzhan ◽

Samad Sepasgozar

Keyword(s):

Digital Elevation Model ◽

Urban Growth ◽

Urban Areas ◽

Future Directions ◽

3D Data ◽

Contour Lines ◽

Digital Elevation ◽

The Future ◽

Elevation Model ◽

Skewness And Kurtosis

Deriving 3D urban development patterns is necessary for urban planners to control the future directions of 3D urban growth considering the availability of infrastructure or being prepared for fundamental infrastructure. Urban metrics have been used so far for quantification of landscape and land-use change. However, these studies focus on the horizontal development of urban form. Therefore, questions remain about 3D growth patterns. Both 3D data and appropriate 3D metrics are fundamentally required for vertical development pattern extraction. Airborne light detection and ranging (Lidar) as an advanced remote-sensing technology provides 3D data required for such studies. Processing of airborne lidar to extract buildings’ heights above a footprint is a major task and current automatic algorithms fail to extract such information on vast urban areas especially in hilly sites. This research focuses on proposing new methods of extraction of ground points in hilly urban areas using autocorrelation-based algorithms. The ground points then would be used for digital elevation model generation and elimination of ground elevation from classified buildings points elevation. Technical novelties in our experimentation lie in choosing a different window direction and also contour lines for the slant area, and applying moving windows and iterating non-ground extraction. The results are validated through calculation of skewness and kurtosis values. The results show that changing the shape of windows and their direction to be narrow long squares parallel to the ground contour lines, respectively, improves the results of classification in slant areas. Four parameters, namely window size, window shape, window direction and cell size are empirically chosen in order to improve initial digital elevation model (DEM) creation, enhancement of the initial DEM, classification of non-ground points and final creation of a normalised digital surface model (NDSM). The results of these enhanced algorithms are robust for generating reliable DEMs and separation of ground and non-ground points in slant urban scenes as evidenced by the results of skewness and kurtosis. Offering the possibility of monitoring urban growth over time with higher accuracy and more reliable information, this work could contribute in drawing the future directions of 3D urban growth for a smarter urban growth in the Smart Cities paradigm.

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Glacial Isostatic Adjustment of the Laurentian Great Lakes Basin: Using the Empirical Record of Strandline Deformation for Reconstruction of Early Holocene Paleo-Lakes and Discovery of a Hydrologically Closed Phase*

Géographie physique et Quaternaire ◽

10.7202/014754ar ◽

2007 ◽

Vol 59 (2-3) ◽

pp. 187-210 ◽

Cited By ~ 33

Author(s):

C.F. Michael Lewis ◽

Steve M. Blasco ◽

Pierre L. Gareau

Keyword(s):

Great Lakes ◽

Response Surface ◽

Lake Michigan ◽

Vertical Motion ◽

Water Levels ◽

Early Holocene ◽

Great Lakes Basin ◽

Isostatic Adjustment ◽

Digital Elevation ◽

Elevation Model

Abstract In the Great Lakes region, the vertical motion of crustal rebound since the last glaciation has decelerated with time, and is described by exponential decay constrained by observed warping of strandlines of former lakes. A composite isostatic response surface relative to an area southwest of Lake Michigan beyond the limit of the last glacial maximum was prepared for the complete Great Lakes watershed at 10.6 ka BP (12.6 cal ka BP). Uplift of sites computed using values from the response surface facilitated the transformation of a digital elevation model of the present Great Lakes basins to represent the paleogeography of the watershed at selected times. Similarly, the original elevations of radiocarbon-dated geomorphic and stratigraphic indicators of former lake levels were reconstructed and plotted against age to define lake level history. A comparison with the independently computed basin outlet paleo-elevations reveals a phase of severely reduced water levels and hydrologically-closed lakes below overflow outlets between 7.9 and 7.0 ka BP (8.7 and 7.8 cal ka BP) in the Huron-Michigan basin. Severe evaporative draw-down is postulated to result from the early Holocene dry climate when inflows of meltwater from the upstream Agassiz basin began to bypass the upper Great Lakes basin.

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Controller for a Low-Altitude Fixed-Wing UAV on an Embedded System to Assess Specific Environmental Conditions

International Journal of Aerospace Engineering ◽

10.1155/2020/1360702 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Johannes von Eichel-Streiber ◽

Christoph Weber ◽

Jesús Rodrigo-Comino ◽

Jens Altenburg

Keyword(s):

Embedded System ◽

Environmental Conditions ◽

Plant Density ◽

Future Research ◽

Digital Elevation ◽

Small Uav ◽

Aerial Vehicle ◽

Low Costs ◽

Low Altitude ◽

Elevation Model

The use of an appropriate sensor on an unmanned aerial vehicle (UAV) is vital to assess specific environmental conditions successfully. In addition, technicians and scientists also appreciate a platform to carry the sensors with some advantages such as the low costs or easy pilot management. However, extra requirements like a low-altitude flight are necessary for special applications such as plant density or rice yield. A rotary UAV matches this requirement, but the flight endurance is too short for large areas. Therefore, in this article, a fixed-wing UAV is used, which is more appropriate because of its longer flight endurance. It is necessary to develop an own controller system to use special sensors such as Lidar or Radar on the platform as a multifunctionality system. Thereby, these sensors are used to generate a digital elevation model and also as a collision avoidance sensor at the same time. To achieve this goal, a small UAV was equipped with a hardware platform including a microcontroller and sensors. After testing the system and simulation, the controller was converted into program code to implement it on the microcontroller. After that, several real flights were performed to validate the controller and sensors. We demonstrated that the system is able to work and match the high requirements for future research.

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