• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.30-39
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• 2023

Large dams, which are critical infrastructures for disaster prevention, are exposed to various risks such as aging, floods, and earthquakes. Better dam safety inspection and diagnosis using digital transformation technologies are needed. Traditional visual inspection methods by human inspectors have several limitations, including many inaccessible areas, danger of working at heights, and know-how based subjective inspections. In this study, drone photogrammetry was performed on two large dams to evaluate the applicability of digital data-based dam safety inspection and propose a data management methodology for continuous use. High-quality 3D digital models with GSD (ground sampling distance) within 2.5 cm/pixel were generated by flat double grid missions and manual photography methods, despite reservoir water surface and electromagnetic interferences, and severe altitude differences ranging from 42 m to 99.9 m of dam heights. Geometry profiles of the as-built conditions were easily extracted from the generated 3D mesh models, orthomosaic images, and digital surface models. The effectiveness of monitoring dam deformation by photogrammetry was confirmed. Cracks and deterioration of dam concrete structures, such as spillways and intake towers, were detected and visualized efficiently using the digital 3D models. This can be used for safe inspection of inaccessible areas and avoiding risky tasks at heights. Furthermore, a methodology for mapping the inspection result onto the 3D digital model and structuring a relational database for managing deterioration information history was proposed. As a result of measuring the labor and time required for safety inspection at the SYG Dam spillway, the drone photogrammetry method was found to have a 48% productivity improvement effect compared to the conventional manpower visual inspection method. The drone photogrammetry-based dam safety inspection is considered very effective in improving work productivity and data reliability.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.526-528
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• 2003

There are some reports which are about measuring the discontinuity from 3D model of rock surface. To generate 3D model is mainly based on remote sensing technique like laser scanning and digital stereo photogrammetry. It is obtained the DEM of the rock slope using above techniques in this study, and examined a suitability and improvement of the photogrammetry for the rock slope by overlap the DEM. It seems that accuracy of DEM generated by photogrammetry technique is influenced by the geometry of rock and type of joint.

• Journal of Korean Society for Geospatial Information Science
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• v.8 no.2 s.16
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• pp.89-99
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• 2000

The Quality and Accuracy of digital image is important factor for decision of accuracy in digital photogrammetry because all the inside works in digital photogrammetry are based on digital image. But it is still difficult to ensure quality assurance and appication of data because there is no distinct criterion about quality and accuracy of digital image when the works in digital photogrammetry is accomplished. This study presents optimal resolution of aerial photo through error analysis of image coordinate using auto inner orientation in digital photograrnrnetry workstation. In second step, we are valified to optimum resolution of aerial photo image with orientation analysis. Finally, we are established to validity optimal resolution of aerial photo image with production of ortho image and mosaic image using optimal resolution aerial photo image.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.233-238
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• 2004

This study deals with the extraction of highway's superelevation using digital imagery which are economic method in constructing database for the side of highway management. Using CCD camera, both center line and shoulder of highway are measured by analyzing the result value and enough result values were obtained. This study is expected to become effective method for extraction of highway alignment elements in the Digital Photogrammetry.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.227-232
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• 2004

In this study, we extracted road surface information which are required highway pavement management system from the obtained digital imagery and these digital image data were analyzed. Thus, this paper says the higyway surface management system and information of surface conditions which are required to management of highway pavement

• 한국공간정보시스템학회:학술대회논문집
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• 2005.11a
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• pp.29-34
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• 2005

Aerial photogrammetry, which is one of the most frequent used technology in mapping and surveying, has been appreciated for its work flow and accuracy to generate 2D and 3D geospatial data. In aerial photograrnrnetry, more than two photographs are taken over the same target area in different position with overlap. Using these photographs and minimum number of ground control points, 3D stereo model is so formed that the ground surface in reality is reconstructed through analogue/analytical plotter or digital photogrammetry system. In case of digital photogrammetry system, 3D geospatial data could be automatically extracted in partial. Recently, in the advent of aerial digital camera such as ADS40 and DMC, digital photogrammetry system will be in the frist place for generating 3D geospatial data. In this paper, we experimentally generated 3D geospatial data using digital photograrnrnetry system in the aspect of work flow.

• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.4
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• pp.155-161
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• 2018

Recently, the development of sensor technology has led to an increase in research on unmanned aerial photogrammetry in various fields such as digital mapping, monitoring, cadastral survey, coastal survey, and topographic survey. However, existing studies are mainly limited experiments and analysis of specific application field, which is insufficient to demonstrate the validity of unmanned aerial photogrammetry for geospatial information construction. In this study, the studies related to the accuracy of unmanned aerial photogrammetry were investigated. The flight altitude and accuracy of horizontal direction is proportional to the GSD by analyzing the results of the individual studies conducted on the unmanned aerial photogrammetry within the last 5 years. In addition, the accuracy of the evaluation results varied widely according to the experimental conditions, and the problems of the previous studies that lacked the number of samples to evaluate the results were identified. A total accuracy analysis of 322 checkpoints yielded an accuracy of 0.028m in the horizontal direction and 0.044m in the vertical direction. In the future, the results of this study can be used as a basis for the validity of spatial information construction using unmanned aerial photogrammetry.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.2 s.10
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• pp.87-97
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• 1997

For real-time data Process of digital images, all things that related to problem-domain are understood individual object and then it Is necessary to program using object oriented approach to grasp all problem as a objects operation by means of message transmission among objects. In this study, for digital photogrammetry class is designed using object oriented programming and class hierarchy is established Also, it is very useful to construct to digital photogrammetry system using class library when it is applied to close range photogrammetry.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.151-159
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• 2003

This study presents method for self-calibration of the SEM(Scanning Electron Microscope) stereo image using the standard microprobe with same grid pattern and using parallel and central perspective projection equation. Result showed that parallel projection method is more suitable for standard microprobe. The maximum error of 3D coordinates acquired by this method did not exceed 5 $\mu\textrm{m}$, and DSM(Digital Surface Model) for three dimensional measurement of the rock sample was generated by the digital photogrammetry. This result can be used for quantification of micro scale change of shape and analysis of the micro morphology of rock due to weathering.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.331-337
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• 2003