• Spatial Information Research
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• v.19 no.1
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• pp.51-59
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• 2011

We produced true ortho images after interpolating occlusion areas and relief displacement of building as well as producing ortho-images to use backward image of ADS which is a aerial digital camera of line type. Also, I was able to produce high quality ortho-images using a small mount of Ground Control Points(GCP) relatively to compare to frame type camera from the evaluation of horizontal position accuracy using ground check points, photo control points for the verification of ortho-images and true-ortho images. Also, I was able to verify the effectiveness in interpolating occlusion areas cause the length overlap was 100% when producing true-ortho images of line type camera.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.20 no.1
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• pp.13-19
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• 2002

In a different way of satellite image or aerial photo, the image acquired by terrestrial photogrammetry has to go through complicated management according to the desired precision and analysis range. In this study, digital surface model and ortho image for cultural asset, terrestrial structures, were made by reflectorless total station in order to increase the application of single photo, and that was analyzed and compared with the method using stereo image. Single photo is expected to be utilized as the measuring method for drawing cultural assets or examining the stability of slope in which high precision doesn't need by performing the various geometric and visual analysis using ortho image made by excluding the difficulties of acquisition and plotting of stereo image.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.6
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• pp.633-641
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• 2008

This study introduces the method of detecting and restoring occlusion areas by using epipolar algorithm and K-means classification algorithm for true ortho-photo generation. In the past, the techniques of detecting occlusion areas are using the reference images or information of buildings. But, in this study the occlusion areas can be automatically detected by using DTM data and exterior orientation parameters. The detected occlusion areas can be restored by using anther images or the computed values which are determined in K-means classification algorithm. In addition, this method takes advantages of applying epipolar algorithm in order to find same location in overlapping areas among images.

• Korean Journal of Remote Sensing
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• v.37 no.6_3
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• pp.2001-2010
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• 2021

The purpose of this study is to efficiently improve orthorectification of KOMPSAT images. As the development of domestic and abroad earth observation satellites accelerates, the number and amounts of satellite images acquired are rapidly increasing. Accordingly, various studies are being conducted to improve orthorectification for the acquired image more quickly and efficiently. This study focused on enhancing processing efficiency through algorithm improvement, except for improving hardware computing capabilities such as GPU. Accordingly, the algorithm was improved with the LUT-based RFM method, and compared and analyzed in terms of accuracy and time-efficiency that vary depending on offset settings.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.30-30
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• 2018

Research on mapping levees is an important task for assessing levee stability. The drone imagery acquired in river basins is useful for generating real-time levee maps. This research proposes a robust methodology for mapping levees in river basins using the drone imagery. In the first step, the multiple imagery taken in the test bed was acquired by the drone. Then, the orthorectified image and DEM (Digital Elevation Model) were generated by the photogrammetry and image processing process. Finally, the significant features on levee surfaces such as levee tops, levee lines, levee slopes, eroded areas were detected from the generated DEM and orthorectified image by manual labors and automatic methods. In future research, the automatic procedure for identifying the significant levee features from the drone imagery would be proposed.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.143-149
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• 2014

The Disaster planning for the reservoir should be more quickly and intuitively establish measures by means of the sequential monitoring of change status of the reservoir water level and water surface area. This paper presents an approach using the orthophoto image produced by the periodic unmanned aerial photogrammetry and analyzed the feasibility. Total three time of unmanned aerial survey were conducted to make orthophoto images for the Seongnae reservoir and we analyzed the amount of changes for water level and surface area compare with each images. As the Analysis results, it was possible to effectively observe the increase in the water level rises and the surface area due to the rainfall. The maximum deviations of orthophoto images was 7.5cm in X-direction, 10.8cm in Y-direction and 14.1cm in elevation compare with ground surveying results. Therefore, we conclude that the unmanned aerial photogrammetry could be applied with comprehensive reservoir monitoring works for disaster management for reservoir in the future. And, the orthophoto production takes about two hours to shoot the images, and approximately four hours is considered for the image processing. So, the unmanned aerial photogrammetry is considered to be the best disaster work that requires urgent because analysis is possible in the shooting day.

• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.1
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• pp.84-93
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• 2011

Levee line mapping is critical to the protection of environments in river zones, the prevention of river flood and the development of river zones. Use of the remote sensing data such as LiDAR and aerial orthoimage is efficient for river mapping due to their accessibility and higher accuracy in horizontal and vertical direction. Airborne laser scanning (LiDAR) has been used for river zone mapping due to its ability to penetrate shallow water and its high vertical accuracy. Use of image source is also efficient for extraction of features by analysis of its image source. Therefore, aerial orthoimage also have been used for river zone mapping tasks due to its image source and its higher accuracy in horizontal direction. Due to these advantages, in this paper, research on three dimensional levee line mapping is implemented using LiDAR and aerial orthoimage separately. Accuracy measurement is implemented for both extracted lines generated by each data using the ground truths and statistical comparison is implemented between two measurement results. Statistical results show that the generated 3D levee line using LiDAR data has higher accuracy than the generated 3D levee line using aerial orthoimage in horizontal direction and vertical direction.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.427-434
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• 2019

In the present study, we assessed the parallel computing performance of Agisoft Metashape for orthomosaic generation, which can implement aerial triangulation, generate a three-dimensional point cloud, and make an orthomosaic based on SfM (Structure from Motion) technology. Due to the nature of SfM, most of the time is spent on Align photos, which runs as a relative orientation, and Build dense cloud, which generates a three-dimensional point cloud. Metashape can parallelize the two processes by using multi-cores of CPU (Central Processing Unit) and GPU (Graphics Processing Unit). An orthomosaic was created from large UAV (Unmanned Aerial Vehicle) images by six conditions combined by three parallel methods (CPU only, GPU only, and CPU + GPU) and two operating systems (Windows and Linux). To assess the consistency of the results of the conditions, RMSE (Root Mean Square Error) of aerial triangulation was measured using ground control points which were automatically detected on the images without human intervention. The results of orthomosaic generation from 521 UAV images of 42.2 million pixels showed that the combination of CPU and GPU showed the best performance using the present system, and Linux showed better performance than Windows in all conditions. However, the RMSE values of aerial triangulation revealed a slight difference within an error range among the combinations. Therefore, Metashape seems to leave things to be desired so that the consistency is obtained regardless of parallel methods and operating systems.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.3
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• pp.283-290
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• 2016

Even though existing methods for orthophoto production in traditional photogrammetry are effective in large areas, they are inefficient when dealing with change detection of geometric features and image production for short time periods in small areas. In recent years, the UAV (Unmanned Aerial Vehicle), equipped with various sensors, is rapidly developing and has been implemented in various ways throughout the geospatial information field. The data and imagery of specific areas can be quickly acquired by UAVs at low costs and with frequent updates. Furthermore, the redundancy of geospatial information data can be minimized in the UAV-based orthophoto generation. In this paper, the orthophoto and DEM (Digital Elevation Model) are generated using a standard low-end UAV in small sloped areas which have a rather low accuracy compared to flat areas. The RMSE of the check points is σ_H = ±0.12 m on a horizontal plane and σ_V = ±0.09 m on a vertical plane. As a result, the maximum and mean RMSE are in accordance with the working rule agreement for the airborne laser scanning surveying of the NGII (National Geographic Information Institute) on a 1/500 scale digital map. Through this study, we verify the possibilities of the orthophoto generation in small slope areas using general-purpose low specification UAV rather than a high cost surveying UAV.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.32 no.4
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• pp.73-84
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• 2014

This research has conducted historical data analysis and on-site investigation on Chungam Pavilion and Seokchun Valley in Bonghwa. Based on the results, the original planting form was identified, and the vegetation management were drawn up. The results of this study can be summarized as follows. First of all, The Book of Seokchun states that there used to be forest trees such as pine tree, saw-leaf zelkova and maple tree, and flowering trees such as peony, royal azalea, rose, chrysanthemum, and lotus, planted around Chungamjeong. Around Seokchunjeongsa, there used to be boxwood, bamboo, maple, peach, gooseberry and peony planted in the area. Through this discovery it can be realized that the vicinity of Chungam Pavilion and Seokchunjeongsa provided not only the grand aesthetics of four clear seasons, but also planting landscapes with various symbolistic significance and meanings. The description of the planting situation in the historical records offers a useful reference for future vegetation management in Chungam Pavilion, Seokchunjeongsa and surrounding valleys. Furthermore, it holds critical value in the identification of planting pattern in late Chosun dynasty. Second, the planting landscape in and around Chungam Pavilion and Seokchunjeongsa will have to be maintained as described in the historical records The Book of Seokchun. Also, the once famous colony of pine trees in the area is gradually reducing in its scale, which calls for active management measures such as elimination of broadleaf trees.