• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2004.03a
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• pp.529-534
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• 2004

고해상도 위성영상을 이용하여 수치지도를 제작함에 있어 가장 큰 문제점은 레스터 자료인 위성영상에서 경계검출을 통해 벡터자료의 형태로 제작하는 어려움이 있다. 본 연구에서는 경계검출을 통하여 위성영상에서 지형의 경계를 검출해내고, 이를 스크린 디지 타이징 기법을 적용하여 벡터라이징 한 후 나타난 결과를 국토지리정보원의 수치지도와 비교하여 정확도를 비교ㆍ평가하였다. 대상 범위는 대전광역시 유성구 가정동 일부지역을 IKONOS로 촬영된 공간해상도 1m의 위성영상을 사용하였다. 위성영상의 전처리는 기하보정과 정사보정을 거친 후 영상강조를 하였고, 여러 가지의 필터링을 적용하여 경계검출을 수행하였다. 경계검출 방법 중에 하나인 Sobel 연산자를 적용한 후 축척 1:5,000 수치지도와의 중첩을 통하여 표준편차(Root Mean Square Error : RMSE)를 산출하여 비교ㆍ분석하였다. 그리고 스크린 디지타이징 기법을 적용하여 추출한 벡터자료를 건물, 도로 및 임야로 분류하여 수치지도와 중첩하여 정확도를 분석하였다. 그 결과 건물과 도로의 경우에는 공공측량 작업규정에서 정하고 있는 축척 1:5,000의 평면위치 허용오차 기준을 만족하고 있지만, 임야의 경우는 축척 1:10,000 이상의 허용오차기준에 만족되고 있음을 알 수 있었다.

• Progress in Medical Physics
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• v.19 no.4
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• pp.209-218
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• 2008

According to improved radiation therapy technology such as IMRT and proton therapy, the accuracy of patient alignment system is more emphasized and IGRT is dominated research field in radiation oncology. We proposed to study the feasibility of cone-beam CT system using simple x-ray imaging systems for image guided proton therapy at National Cancer Center. 180 projection views ($2,304{\times}3,200$, 14 bit with 127 ${\mu}m$ pixel pitch) for the geometrical calibration phantom and humanoid phantoms (skull, abdomen) were acquired with $2^{\circ}$ step angle using x-ray imaging system of proton therapy gantry room ($360^{\circ}$ for 1 rotation). The geometrical calibration was performed for misalignments between the x-ray source and the flat-panel detector, such as distances and slanted angle using available algorithm. With the geometrically calibrated projection view, Feldkamp cone-beam algorithm using Ram-Lak filter was implemented for CBCT reconstruction images for skull and abdomen phantom. The distance from x-ray source to the gantry isocenter, the distance from the flat panel to the isocenter were calculated as 1,517.5 mm, 591.12 mm and the rotated angle of flat panel detector around x-ray beam axis was considered as $0.25^{\circ}$. It was observed that the blurring artifacts, originated from the rotation of the detector, in the reconstructed toomographs were significantly reduced after the geometrical calibration. The demonstrated CBCT images for the skull and abdomen phantoms are very promising. We performed the geometrical calibration of the large gantry rotation system with simple x-ray imaging devices for CBCT reconstruction. The CBCT system for proton therapy will be used as a main patient alignment system for image guided proton therapy.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.601-605
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• 2009

Due to the fact that fish-eye lens can provide super wide angles with the minimum number of cameras, field-of-view over 180 degrees, many vehicles are attempting to mount the camera system. Camera calibration should be preceded, and geometrical correction on the radial distortion is needed to provide the images for the driver's assistance. However, vehicle fish-eye cameras have diagonal output images rather than circular images and have asymmetric distortion beyond the horizontal angle. In this paper, we introduce a camera model and metric calibration method for vehicle cameras which uses feature points of the image. And undistort the input image through a perspective projection, where straight lines should appear straight. The method fitted vehicle fish-eye lens with different field of views.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.1
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• pp.63-68
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• 2006

Time series of waterline changes during a flood/ebb cycle can be utilized for supplementary data for measuring bottom topography. The waterlines extracted from consecutive images are substituted for depth contours using water level data. The distances between contours are quantified through a rectification image process. This technique is applied to the Keunpoolan beach in the Daeijak Island near Incheon. A camera monitoring technique supported by natural water level changes produces bottom topography with high precision. It is also less time consuming and more economical. The technique also can be utilized effectively to the physical modeling f3r measuring bottom changes in the three dimensional basin.

• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.85-98
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• 1997

A geometric model of pushbroom-type linear CCD camera images is proposed in this paper. At present, this type of cameras are used for obtaining almost all kinds of high-resolution optical images from satellites. The proposed geometric model includes not only a forward transformation which is much more efficient. An inverse transformation function cannot be derived analytically in a closed form because the focal point of an image varies with time. In this paper, therefore, an iterative algorithm in which a focal point os converged to a given pixel position is proposed. Although the proposed model can be applied to any pushbroom-type linear CCD camera images, the geometric model of the high-resolution multi-spectral camera on-board KITSAT-3 is used in this paper as an example. The flight model of KITSAT-3 is in development currently and it is due to be launched late 1998.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.1
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• pp.61-68
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• 2016

Digital aerial images have been commonly used in a large scale map production owing to their excellent geometry, and high spatial and radiometric resolution in recent years. However, a quality verification process for acquired images should be preceded in order to secure the high precision and reliability of produced results. Several experimental studies to verify digital imaging systems have been vigorously researched by constructing permanent test field in abroad. On the other hand, it is urgently necessary to suggest a practical scheme for an image quality verification, because this related study and experiment are still in its early stage at home. Hence, this study aims to present an easy method to measure the spatial resolution of the image in a visual way using a portable Siemens star. The images used in the study were obtained with three different cameras, two frame array sensors of DMC, UltraCamXp and a linear array sensor of ADS80. The Siemens star target appeared in every image is extracted and then the spatial resolution of image is compared with theoretical GSD(Ground Sample Distance) by a visual method. In addition, the change of spatial resolution depending on the location of the Siemens star from image center and flight direction and cross-flight direction is also compared and analyzed. As study results, while the theoretical GSDs of images taken with each camera are about 6~9cm, the visual resolutions are 1.2~1.3 times as great as the theoretical ones.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1416-1419
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• 2015

최근 건강에 대한 일반인들의 관심이 증가하면서 스마트 헬스케어 시장 규모가 기하급수적으로 커지고 있다. 특히 탈모 관련 헬스케어 시장의 경우, 국내 탈모 인구의 증가로 인해 탈모의 예방이나 관리 등 탈모 관련 어플리케이션이 빠르게 등장하고 있다. 모발 밀도는 탈모의 정도를 판단하기 위한 가장 기본적인 모발 특징 중 하나이지만, 모발의 밀도를 측정하기 위한 명확한 영상처리 기법이나 소프트웨어의 개발은 여전히 미진한 상태이다. 이에 본 논문에서는 스마트폰에 탈부착이 가능한 포터블 카메라에서 촬영된 두피 모발 현미경 영상에서 모발의 밀도를 측정하고 이를 기반으로 사용자 중심의 탈모 진단 플랫폼을 구축하고자 한다. 모발 밀도의 측정은 Contrast Stretching과 Morphology Processing을 이용한 전처리, 스켈레톤 이미지의 변환, 그리고 라인 끝점 검색 알고리즘의 적용 등 크게 세 단계로 진행된다. 제안하는 기법의 성능 평가를 위해, 50배율 포터블 카메라로 촬영한 두피 영상 30개에 대해 밀도 측정을 수행하였으며 그 결과 92.88%의 정확도를 얻었다. 결과적으로 제안하는 기법은 단순 두피 현미경 영상으로 탈모의 지표가 될 수 있는 모발 밀도를 측정하는 데 충분히 효과적임을 알 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.194-196
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• 2017

최근 들어 VR 관련 기술이 발전하고 대중화가 됨에 따라 VR 하드웨어 기술 이외에도 VR 영상에 대한 개발과 연구에 대한 관심이 증가하고 있다. 이러한 VR 영상을 제작하기 위해서는 360 도의 전방위 촬영, 영상의 스티칭 및 프로젝션 그리고 사용자의 시야점획득을 통한 렌더링등과 같은 기술이 필요하다. 그러나 영상들의 스티칭, 프로젝션 등의 여러 단계의 과정을 거치면서 원 영상에 비하여 많은 왜곡이 발생하게 된다. 따라서 본 논문에서는 이러한 제작과정 중 발생하는 기하학적 왜곡에 대해 분석한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.2
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• pp.165-172
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• 2013

In this paper, high-quality mosaic image is generated by high-resolution hyperspectral strip images using scale-invariant feature transform (SIFT) algorithm, which is one of the representative image matching methods. The experiments are applied to AISA Eagle images geo-referenced by using GPS/INS information acquired when it was taken on flight. The matching points between three strips of hyperspectral images are extracted using SIFT method, and the transformation models between images are constructed from the points. Mosaic image is, then, generated using the transformation models constructed from corresponding images. Optimal band appropriate for the matching point extraction is determined by selecting representative bands of hyperspectral data and analyzing the matched results based on each band. Mosaic image generated by proposed method is visually compared with the mosaic image generated from initial geo-referenced AISA hyperspectral images. From the comparison, we could estimate geometrical accuracy of generated mosaic image and analyze the efficiency of our methodology.

• Spatial Information Research
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• v.9 no.1
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• pp.1-13
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• 2001

Nowadays, SAR Interferometry is actively being studied as a new technique in topographic mapping using satellite imagery. It extracts height values using phase information derived by two SAR imageries covering same areas. Unlike when using SPOT imagery, it is not affected by atmospheric conditions and time. So to speak, we can say that SAR Interferometry is flexible in imagery acquisitions and can get height data economically over wide area. So, it is expected that SAR Interferometry will be widely using in GIS applications. But, in some area occurring geometric distortion, height data are misjudged or not extracted depending on phase unwrapping algorithms. IN the case of ERS tandem data, the accuracy of height data was worst in mountain area. It is the because of the short incidence angle resulted in layover effect. Of the phase unwrapping algorithms, path-following was better in height accuracy but could not get data in layover area. In this area, we could get height data using Height Sensitivity. In concludion, we could get DEM that maintained the accuracy of path-following method and have overall data across imagery.