scholarly journals AN APPROACH TO POSITIONAL QUALITY CONTROL METHODS FOR AIRBORNE INSAR HIGH-RESOLUTION X-BAND ORTHOIMAGES AND P-BAND DIGITAL TERRAIN MODEL

2021 ◽  
Vol 27 (1) ◽  
Author(s):  
Gleice Pereira da Silva ◽  
Roberto Quental Coutinho ◽  
Rafael Antonio da Silva Rosa
Keyword(s):  
Digital Terrain Model ◽  
Synthetic Aperture ◽  
Control Points ◽  
Terrain Model ◽  
Class A ◽  
Data Process ◽  
Digital Terrain ◽  
Optical Images ◽  
X Band ◽  
Positional Control

Abstract: The positional validation of datasets is an important step for cartography studies since it allows learning about its accuracy, and also indicates the data process quality. However, the positional validation of Synthetic Aperture Radar (SAR) datasets have some additional challenges when compared to optical images due to the geometric distortions. We employ existing targets such as traffic signs and lampposts in the scene and identify them on the image as control points. We performed the validation of the geographic coordinates used as planialtimetric positional control points, using both the amplitude backscattering orthoimage and the Digital Terrain Model (DTM) generated from the InSAR system. We employed the NMAS, ASPRS and NSSDA tests along with information by the Brazilian Standards. This validation showed these control points presented the following results for 1:10,000 scale: NMAS test - class “A” in PEC and PEC-PCD; ASPRS test - RMSE x = 1.317m, RMSE y = 1.231m and RMSE z = 1.145m; and NSSDA test - RMSE r = 1,802m, Precision r = 3.118m and Precision z = 2.244m. These results prove we can use the proposed targets as control points and the used InSAR datasets meet the expected quality for generation of geotechnic products for 1:10,000 scale.

Research on Algorithm of Delaunay Triangulation Net Interpolating the Best Point

2014 ◽  
Vol 1044-1045 ◽  
pp. 1278-1282
Author(s):  
Xing Guo Qiu ◽  
Zheng Liu
Keyword(s):  
Delaunay Triangulation ◽  
Complex Terrain ◽  
Three Dimensional ◽  
Digital Terrain Model ◽  
Kriging Interpolation ◽  
Control Points ◽  
Interpolation Algorithm ◽  
Terrain Model ◽  
Digital Terrain ◽  
Technological Tool

Aiming at the folds caused by the sparse data in the process of DTM (Digital Terrain Model), this article proposed a method of interpolating spatial control points based on Delaunay triangulation and Kriging interpolation algorithm. The terrain data of an area with complex terrain in Xianyang was used to construct terrain model according to the proposed algorithm. Experimental results show that the method can finish the interpolation of the terrain denser data quickly and accurately, and it provides an efficient technological tool for building a true three-dimensional terrain model.

Development of a 3D Viewer for georeferencing and monoplotting of historical terrestrial images.

2020 ◽  
Author(s):  
Sebastian Flöry ◽  
Camillo Ressl ◽  
Gerhard Puercher ◽  
Norbert Pfeifer ◽  
Markus Hollaus ◽  
...  
Keyword(s):  
Digital Terrain Model ◽  
Local Scale ◽  
Aerial Imagery ◽  
Ground Control ◽  
Control Points ◽  
Mountainous Regions ◽  
Terrain Model ◽  
Digital Terrain ◽  
Ground Control Points ◽  
Selection Of

<p>Mountain regions are disproportionately affected by global warming and changing precipitation conditions. Especially the strong variations within high mountain ranges at the local scale require additional sources in order to quantify changes within this challenging environment. With the emergence of alpine tourism, terrestrial photographs became available by the end of 1800, predating aerial imagery for the selected study areas by 50 years. Due to the earlier availability and oblique acquisition geometry these images are a promising source for quantifying changes within mountainous regions at the local scale. Within the research project SEHAG, methods to process these images and to analyse their potential to quantify and describe environmental changes are developed and applied to study areas in Austria and Italy.</p><p>One of the prerequisites for the estimation of changes based on terrestrial imagery is the calculation of the corresponding object point for each pixel in a global coordinate system resulting in a georeferenced orthorectified image. This can be achieved by intersecting the ray defined by the projection center of the camera and each pixel with a digital terrain model, a process known as monoplotting.</p><p>So far 1000 terrestrial images with unknown interior and exterior orientation have been collected from various archives for the selected study areas Kaunertal, Horlachtal (both Tyrol, Austria) and Martelltal (South Tyrol, Italy). In order to estimate all camera parameters a 3D viewer for the selection of ground control points has been developed and implemented. The estimation of the exterior and interior orientation is done in OrientAL. </p><p>Preliminary results for selected images show, that especially the developed 3D viewer is an important improvement for the selection of well distributed ground control points and the accurate estimation of the exterior and interior orientation. Monoplotting depends on a digital terrain model, which cannot be computed from the terrestrial images alone due to missing overlap and different acquisitions times. Hence, the combination with historical digital terrain models derived from aerial imagery is necessary to minimize errors introduced due to changes in topography until today. While the large amount of terrestrial images with their oblique acquisition geometries can be exploited to fill occluded areas by combining the results from multiple images, the partly missing or inaccurate temporal information poses another limitation.</p><p>With this large image collection, for the first time, we are able to evaluate the use of historical oblique terrestrial photographs for change detection in a systematic manner. This will promote knowledge about challenges, limitations and the achievable accuracy of monoplotting within mountainous regions. The work is part of the SEHAG project (project number I 4062) funded by the Austrian Science Fund (FWF).</p>

scholarly journals ACCURACY ANALYSIS OF MEASURING CLOSE-RANGE IMAGE POINTS USING MANUAL AND STEREO MODES

2013 ◽  
Vol 39 (1) ◽  
pp. 18-22 ◽  
Author(s):  
Jūratė Sužiedelytė-Visockienė
Keyword(s):  
3D Model ◽  
Digital Terrain Model ◽  
Image Point ◽  
Range Image ◽  
Control Points ◽  
Image Transformation ◽  
Terrain Model ◽  
Digital Terrain ◽  
Close Range ◽  
Manual Mode

The performed investigations are aimed at estimating the accuracy of image processing using different image point measurements. For this purpose, digital close-range images were processed applying photogrammetric software PhotoMod. The measurements have been made employing two methods: stereo and manual mode. Two or more overlapping images are matched when control and tie points are estimated. The images of two objects have been taken for experimental investigation. Control points and tie points were measured switching either to stereo or manual mode applying the required software. The control points of the first object are distributed on the surface of a smooth facade and on the surface of different (a few) levels. The process of image matching includes the calculation of the correlation coefficient, vertical parallax residuals and the root mean square of the object. Following image transformation (adjustment processes) to the created 3D model, the accuracy of the measured points is determined. All these values show the precision of close-range photogrammetric processes. Such accuracy satisfies requirements for creating a proper digital terrain model and orthophoto generation.

scholarly journals DTM GENERATION WITH UAV BASED PHOTOGRAMMETRIC POINT CLOUD

2017 ◽  
Vol XLII-4/W6 ◽  
pp. 77-79 ◽  
Author(s):  
N. Polat ◽  
M. Uysal
Keyword(s):  
Low Cost ◽  
Laser Scanner ◽  
Digital Camera ◽  
Digital Terrain Model ◽  
Field Work ◽  
Generation Process ◽  
Control Points ◽  
Terrain Model ◽  
Digital Terrain ◽  
Ground Control Points

Nowadays Unmanned Aerial Vehicles (UAVs) are widely used in many applications for different purposes. Their benefits however are not entirely detected due to the integration capabilities of other equipment such as; digital camera, GPS, or laser scanner. The main scope of this paper is evaluating performance of cameras integrated UAV for geomatic applications by the way of Digital Terrain Model (DTM) generation in a small area. In this purpose, 7 ground control points are surveyed with RTK and 420 photographs are captured. Over 30 million georeferenced points were used in DTM generation process. Accuracy of the DTM was evaluated with 5 check points. The root mean square error is calculated as 17.1 cm for an altitude of 100 m. Besides, a LiDAR derived DTM is used as reference in order to calculate correlation. The UAV based DTM has o 94.5 % correlation with reference DTM. Outcomes of the study show that it is possible to use the UAV Photogrammetry data as map producing, surveying, and some other engineering applications with the advantages of low-cost, time conservation, and minimum field work.

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 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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