• Journal of The Geomorphological Association of Korea
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• v.28 no.4
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• pp.41-52
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• 2021

With the popularization of drones and the ease of use of the Global Navigation Satellite System (GNSS), drone photogrammetry for terrain information has been widely used. Drone photogrammetry enables the realization of high-accuracy three-dimensional topography for the entire area with less effort and time compared to the past direct survey using GNSS or total station. From 3-D topographic data, various topographical analysis is possible. To improve the accuracy of drone photogrammetry, direct GCP surveying in the field is essential, and the numbers and reasonable positioning of GCPs are very important. In the case of beaches or tidal flats on the west coast of Korea, the numbers and location of GCPs are important factors in efficient drone photogrammetry because of the size of the area, difficulties of movement, and the risk from tides. If the RTK (Real-time kinematic) or PPK (Post-processed kinematic) method is used, the increased accuracy of the drone's location enables high-accuracy photogrammetry with a small number of GCPs. This study presents an efficient drone photogrammetry method in terms of time and economy by comparing and analyzing the results of drone photogrammetry using Non-PPK with low-cost PPK-Kit, based on the tests of various numbers and locations of GCPs in the university field including various slopes and structures like coastal terrain.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.239-246
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• 2019

The drone photogrammetry is actively utilized for obtaining highly accurate spatial information and other various monitoring purposes. It is general to plan the drone photogrammetry by referring to previous experiences or cases in order to obtain the required accuracy, but the drone photogrammetry is often carried out again due to poor accuracy. Since the required spatial accuracy of the drone photogrammetry process result becomes the means of objective evaluation regardless of the type of result, it should be determined carefully. Therefore, it is necessary to determine flight height, overlap, number and arrangement of ground control point, and exterior orientation factor acquisition method in order to meet the required 3D positional accuracy for the design of drone photogrammetry project. In this study, previous study cases for the analysis of drone photogrammetry accuracy were carefully analyzed and verified by applying such cases to testing area, and design guideline of drone photogrammetry project for a small area was prepared based on the analysis result. The presented project design guideline is expected to be a great help to business practice although it is not perfect, and if the design guideline is prepared through comprehensive analysis in future, it would be possible to provide a perfect manual.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.121-131
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• 2023

Although the utilization of drone photogrammetry that can generate spatial information using ultra-high-resolution images is increasing in the civil engineering and construction fields, analysis of areas that can be used is insufficient. Therefore, this study attempted to determine how far drone photogrammetry can be used in the civil engineering and construction fields by applying a detailed analysis method. The status map and cross-sectional map were actually vectorized using drone photogrammetry outcomes, compared and analyzed with the results acquired in the field, and the qualitative aspects of traffic safety facilities were analyzed to determine their usability. As a result, the accuracy of the plane position using drone photogrammetry was reliable, but the height accuracy was difficult to trust. Accordingly, although there is a possibility of preparing a status map, the use of it in areas requiring high accuracy such as cross-sectional plans was limited, and it is believed that it can be used in the construction management field where qualitative analysis is conducted.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.1
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• pp.55-63
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• 2021

The roughness of the road is an important factor directly connected to the ride comfort, and is an evaluation item for functional evaluation and pavement quality management of the road. In this study, data on the road surface were acquired using the latest 3D geospatial information construction technology of ground LiDAR, drone photogrammetry, and drone LiDAR, and the accuracy and roughness of each method were analyzed. As a result of the accuracy evaluation, the average accuracy of terrestrial LiDAR were 0.039m, 0.042m, 0.039m RMSE in X, Y, Z direction, and drone photogrammetry and drone LiDAR represent 0.072~0.076m, 0.060~0.068m RMSE, respectively. In addition, for the roughness analysis, the longitudinal and lateral slopes of the target section were extracted from the 3D geospatial information constructed by each method, and the design values were compared. As a result of roughness analysis, the ground LiDAR showed the same slope as the design value, and the drone photogrammetry and drone LiDAR showed a slight difference from the design value. Research is needed to improve the accuracy of drone photogrammetry and drone LiDAR in measurement fields such as road roughness analysis. If the usability through improved accuracy can be presented in the future, the time required for acquisition can be greatly reduced by utilizing drone photogrammetry and drone LiDAR, so it will be possible to improve related work efficiency.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.2
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• pp.81-91
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• 2021

Drone related research has been increasing recently due to the development and distribution of commercial unmanned aerial vehicles. However, most of the previous studies focused on the accuracy and utility of drone surveying. For drones, the resolution of the result is determined according to the flight altitude, but since 70% of Korea is mountainous, it is necessary to analyze the quality of the drone image according to the flight plan. In this study, the quality of drone photogrammetry results according to flight plans was analyzed. The flight plan was established by fixed altitude and considering the height of the terrain. Images were acquired for both cases and data was processed to generate ortho images. As a result of evaluating the accuracy of the generated ortho image, the accuracy was found to be -0.07 ~ 0.09m. The accuracy of Case I and Case II did not show a significant difference, but for RMSE, Case I showed a good value. These results indicate that the drone flight plan affects the quality of the results. Also, when flying at a fixed altitude, II showed a lower value than the originally set overlap according to the altitude of the object. In future surveys using drones, flight planning taking into account the height of the object will contribute to the improvement of the quality of the results.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.3
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• pp.197-202
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• 2018

Drone has been continuously studied in the field of geography and remote sensing. The basic researches have been actively carried out before the utilization in the field of photogrammetry. In Korea, it is necessary to study the actual way of research in accordance with the drone utilization environment. In particular, analysis on the characteristics of DSM (Digital Surface Model) generated through drone are needed. In this study, the characteristic of drone DSM as a data acquisition method was analyzed for coastal management. The coastal area was selected as the study area, and data was acquired by using drone. As a result of the study, the terrain model and the ortho image of coastal area were produced. The accuracy of UAV (Unmanned Aerial Vehicle) results were very high about 10cm at check points. However, concavo-convex shapes appeared in very flat areas such as tidal flats and roads. To correct this terrain model distortion, a new terrain model was created through data processing and the results were evaluated. If additional studies are carried out and the construction and analysis of terrain model using drone image is done, drone data for coastal management will be available.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1145-1153
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• 2023

This study presents the development of pointcloud data integration technology in construction sites via drone photogrammetry and MMS LiDAR. The integration of pointcloud data from drones and MMS technology can provide precise and accurate 3D digital maps of construction sites, which can benefit the development of smart construction and BIM. The advantages of using both drones and MMS technology for pointcloud data acquisition in construction sites are discussed, along with the limitations and challenges of using drone photogrammetry and MMS LiDAR for pointcloud data integration. The results of this study can contribute to the advancement of pointcloud data integration technology in construction sites and improve the efficiency and accuracy of construction projects.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.1
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• pp.47-54
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• 2021

Calculation of quantity at construction sites is a factor that has a great influence on construction costs, and it is important to calculate accurate values. In this study, topographic model was created by using drone photogrammetry and drone LiDAR to estimate earthwork volume. ortho image and DSM (Digital Surface Model) were constructed for the study area by drone photogrammetry, and DEM (Digital Elevation Model) of the target area was established using drone LiDAR. And through accuracy evaluation, accuracy of each method are 0.034m, 0.35m in horizontal direction, 0.054m, 0.25m in vertical direction. Through the research, the usability of drone photogrammetry and drone LiDAR for constructing geospatial information was presented. As a result of calculating the volume of the study site, the UAV photogrammetry showed a difference of 1528.1㎥ from the GNSS (Global Navigation Satellite System) survey performance, and the 3D Laser Scanner showed difference of 160.28㎥. The difference in the volume of earthwork is due to the difference in the topographic model, and the efficiency of volume calculation by drone LiDAR could be suggested. In the future, if additional research is conducted using GNSS surveying and drone LiDAR to establish topographic model in the forest area and evaluate its usability, the efficiency of terrain model construction using drone LiDAR can be suggested.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.2
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• pp.63-70
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• 2019

Electric transmission towers are facilities to transport electrical power from a plant to an electrical substation. The towers are connected using wires considering the wire tension and the clearance from the ground or nearby objects. The wires are installed on a rights-of-way that is a strip of land used by electrical utilities to maintain the transmission line facilities. Trees and plants around transmission lines must be managed to keep the operation of these lines safe and reliable. This study proposed the use of a low-cost drone photogrammetry for the transmission line rights-of-way mapping. Aerial photogrammetry is carried out to generate a dense point cloud around the transmission lines from which a DSM (Digital Surface Model) and DTM (Digital Terrain Model) are created. The lines and nearby objects are separated using nDSM (normalized Digital Surface Model) and the noises are suppressed in the multiple image space for the geospatial analysis. The experimental result with drone images over two spans of transmission lines on a mountain area showed that the proposed method successfully generate the rights-of-way map with hazard nearby objects.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.2
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• pp.73-79
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• 2021

Recently there are growing interests on the energy conservation and emission reduction. In the fields of architecture and civil engineering, the energy monitoring of structures is required to response the energy issues. In perspective of thermal monitoring, thermal images gains popularity for their rich visual information. With the rapid development of the drone platform, aerial thermal images acquired using drone can be used to monitor not only a part of structure, but wider coverage. In addition, the stereo photogrammetric process is expected to generate 3D point cloud with thermal information. However thermal images show very poor in resolution with narrow field of view that limit the use of drone-based thermal photogrammety. In the study, we aimed to generate 3D thermal point cloud using visible and thermal images. The visible images show high spatial resolution being able to generate precise and dense point clouds. Then we extract thermal information from thermal images to assign them onto the point clouds by precisely establishing photogrammetric collinearity between the point clouds and thermal images. From the experiment, we successfully generate dense 3D thermal point cloud showing 3D thermal distribution over the building structure.