• Proceedings of the KSRS Conference
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• v.1
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• pp.98-101
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• 2006

In general, stereo images are widely used to remote sensing or photogrametric applications for the purpose of image understanding and feature extraction or cognition. However, the most cases of these stereo-based application deal with 2-D satellite images or the airborne photos so that its main targets are generation of small-scaled or large-scaled DEM(Digital Elevation Model) or DSM(Digital Surface Model), in the 2.5-D. Contrast to these previous approaches, the scope of this study is to investigate 3-D stereo processing and visualization of true geo-referenced 3-D features based on anaglyph technique, and the aim is at the prototype development for stereo visualization system of complex typed 3-D GIS features. As for complex typed 3-D features, the various kinds of urban landscape components are taken into account with their geometric characteristics and attributes. The main functions in this prototype are composed of 3-D feature authoring and modeling along with database schema, stereo matching, and volumetric visualization. Using these functions, several technical aspects for migration into actual 3-D GIS application are provided with experiment results. It is concluded that this result will contribute to more specialized and realistic applications by linking 3-D graphics with geo-spatial information.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.26-26
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• 2021

본 연구에서는 2020년 산사태가 발생한 곡성지역을 대상으로 무인항공기 사진측량을 통하여 산사태 지역의 범위와 변위를 조사하고 이를 기반으로 산사태에 의한 피해범위를 LS-RAPID에서 분석하였다. LS-RAPID는 지진과 강우의 영향을 반영하는 산사태 시뮬레이션 모델이며, 산사태 운동시작여부를 평가하며 만일 발생 시 토사의 이동, 퇴적 범위, 토사층의 깊이를 예측할 수 있다. 산사태 시뮬레이션에서 중요한 변수 중의 하나는 지중의 활동층의 깊이와 분포이다. 재해현장에서 이런 자료를 신속하고 정량적으로 측정하기 위한 방법으로서 무인항공기를 이용한 측량을 실시하였다. 또한 산사태 토사의 이동과 퇴적을 검증하기 위한 자료도 획득하였다. 매개변수의 추정 시선행연구에서 제시된 값을 참고하여, 재해현장의 피해범위와 규모를 비교하여 매개변수를 추정하여 다른 연구사례에서 이용한 값들과 비교, 분석하였다. 또한, 시뮬레이션의 지형입력자료로서 무인항공기 사진 측량자료에서 생성된 DSM(Digital Surface Model)과 수지지도에서 생성한 DEM(Digital Elevation Model)을 적용한 경우, 시뮬레이션 결과에 영향을 비교, 분석하였다. 결과적으로 DEM보다 DSM을 적용하는 것이 퇴적범위가 크게 확대되지 않으며, 현장을 잘 반영한 결과가 얻어지는 것으로 평가되었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.454-458
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• 2007

Nonpoint source (NPS) pollution is a serious problem causing the degradation of soil and water quality. Concentrated overland flow is the primary transport mechanism for a large amount of NPS pollutants from hillslope areas to downslope areas in a watershed. In this study, a soil erosion model, nLS model, to identify transitional overland flow regions (i.e., ephemeral gully head areas) was developed using the kinematic wave overland flow theory. Spatial data, including digital elevation models (DEMs), soil, and landcover, were used in the GIS-based model algorithm. The model was calibrated and validated using gully head locations in a large agricultural watershed, which were identified using 1-m aerial photography. The model performance was better than two previous approaches; the overall accuracy of the nLS model was 72 % to 87 % in one calibration subwatershed and the mean overall accuracy was 75 to 89 % in four validation subwatersheds, showing that the model well predicted potential transitional erosion areas at different watersheds. However, the user accuracy in calibration and validation was still low. To improve the user accuracy and study the effects of DEM resolution, finer resolution DEMs may be preferred because DEM grid is strongly sensitive to estimating model parameters. Information gained from this study can improve assessing soil erosion process due to concentrated overland flow as well as analyze the effect of microtopographic landscapes, such as riparian buffer areas, in NPS control.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.4
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• pp.261-268
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• 2017

The topographic volume estimation is carried out for the earth work of a construction site and quarry excavation monitoring. The topographic surveying using instruments such as engineering levels, total stations, and GNSS (Global Navigation Satellite Systems) receivers have traditionally been used and the photogrammetric approach using drone systems has recently been introduced. However, these methods cannot be adopted for inaccessible areas where high resolution satellite images can be an alternative. We carried out experiments using Kompsat-3/3A data to estimate topographic volume for a quarry and checked the accuracy. We generated DEMs (Digital Elevation Model) using newly acquired Kompsat-3/3A data and checked the accuracy of the topographic volume estimation by comparing them to a reference DEM generated by timely operating a drone system. The experimental results showed that geometric differences between stereo images significantly lower the quality of the volume estimation. The tested Kompsat-3 data showed one meter level of elevation accuracy with the volume estimation error less than 1% while the tested Kompsat-3A data showed lower results because of the large geometric difference.

• 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.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.553-558
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• 2002

Physical sensor model in pushbroom satellite images can be made from sensor modeling by rotation parameters and attitude parameters on the satellite track. These parameters are determined by the information obtained from GPS, INS, or star tracker. Provided from satellite image, an auxiliary data error is connected directly with an error of rotation parameters and attitude parameters. This paper analyzed how obtaining satellite images influenced errors of rotation parameters and attitude parameters. furthermore, for detailed analysis, this paper generated simulated satellite image, which was changed variously by rotation parameters and attitude parameters of satellite sensor model. Simulated satellite image is generated by using high-resolution digital aerial image and DEM (Digital Elevation Model) data. Moreover, this paper determined correlation of rotation parameter and attitude parameters through error analysis of simulated satellite image that was generated by various rotation parameters and attitude parameters.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.2
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• pp.131-140
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• 2020

Recently the importance of BIM (Building Information Modeling) that enables 3D location-based design and construction work is being highlighted around the world. In Korea, the road map has been established to settle the design based on BIM using drone survey results by 2025. As the first step, BIM would be applied to road construction projects worth more than 50 billion Korean Won from 2020. On the other hand, drone survey regulation has been enacted and the data for drone survey cost were also included on Standard of construction estimate in 2020. However, more careful improvement is required to reflect drone survey results in BIM design and construction. Currently, Engineering instructions and Standard of construction estimate specifies that earthwork volume must be calculated by cross section method only. So it is required to add the method of DEM (Digital Elevation Model) based volume calculation on these regulations to realize BIM application. In order for that, this study verified the method of DEM based earthwork volume calculation. To get an accurate DEM for accurate volume computation, drone survey was carried out according to the drone survey regulation and then could get an accurate DEM data which have errors less than 3cm in X, Y and 6.8cm in H. As each DEM cell has 3D coordinate component, the volume of each cell can be calculated by obtaining the height of area of the cell then total volume is calculated by multiplying total number of cells by volume of each cell for the construction area. Verification for the new calculation method compare with existing method was carried out. The difference between DEM based volume by drone survey and cross section based volume by traditional survey was less than 1.33% and it can be seen that new DEM method will be able to be applied to BIM design and construction instead of cross section method.

• Proceedings of the KSRS Conference
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• 2007.03a
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• pp.97-102
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• 2007

3차원 공간정보는 2차원에 비해 공간적 현실감이 뛰어나기 때문에 최근 경관분석，도시 계획 및 웹(Web) 을 통한 지도 서비스 분야 등에서 이에 대한 관심이 증가하고 있으나，3차원 공간 정보의 기하학적 특성상 기존의 2차원 공간정보에 비해 데이터 량이 방대해 지고 있으며 이를 활용한 또 다른 콘텐츠 제작과 빠르고 효율적인 처리에 많은 문제점을 가지고 있다. 본 논문에서는 이러한 문제점을 해결하기 위한 방법으로 위성 및 항공으로부터 획득한 DEM(Digital Elevation Model)을 이용하여 생성된 3차 원의 지형정보와 도시 모델링 및 텍스처 맵핑 과정을 통해 획득한 정보를 기반으로 하여 각각의 위치에 카메라를 설정하고， 설정된 카메라 위치를 기반으로 Camera Matrix를 구한다. 이렇게 획득한 카메라의 정보엔 깊이 정보를 포함하고 있는데，깊이 정보를 기반으로 하여 3차원의 워핑(Warping)작업을 통해 계층적 핍이 영상(LDI)를 생성하고，생성된 계층적 깊이 영상을 이용하여 3차원의 공간정보를 구현한다.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.279-282
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• 2010

최근 단일 고해상도 위성영상과 건물과 지형에 대한 정보를 가지고 있는 수치지도(DEM:Digital Elevation Model)를 이용하여 3차원 영상으로 구축하는 연구가 많이 이루어지고 있다. 3차원영상을 구축하기 위해서는 건물과 지형의 위치, 크기, 형상에 관한 정보가 필요하나 위성영상만으로는 구하기가 어려워 수치지도를 활용한다. 본 논문에서는 수치지도를 이용하여 3차원 건물과 지형의 고도 정보를 추출하고, 위성영상과 Snake 모델을 이용하여 반자동으로 추가적인 건물 높이와 바닥면에 대한 정보를 추출하여, 3차원 영상을 생성 하는 방법을 제안한다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.4
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• pp.267-273
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• 2005

Stereo image analysis has been an important tool for reconstructing 3D terrain. By In its nature, occlusion is one of difficulties Ive cannot avoid in stereo matching. This paper presents a study on occlusion detection by employing LRC(Left-Right Check) and OCC(Occlusion Constraint) and how we can improve the accuracy of DEM(Digital Elevation Model) y using interpolated data into the detected occluded area. Experimental results show that these method can effectively detect occluded regions and improve the accuarcy of DEM using the occlusion detection.