• 대한전기학회논문지:시스템및제어부문D
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• 제53권4호
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• pp.277-285
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• 2004

We present a new hybrid stereo matching technique in terms of the co-operation of area-based stereo and feature-based stereo. The core of our technique is that feature matching is carried out by the reference of the disparity evaluated by area-based stereo. Since the reference of the disparity can significantly reduce the number of feature matching combinations, feature matching error can be drastically minimized. One requirement of the disparity to be referenced is that it should be reliable to be used in feature matching. To measure the reliability of the disparity, in this paper, we employ the self-consistency of the disunity Our suggested technique is applied to the detection of 3D line segments by 2D line matching using our hybrid stereo matching, which can be efficiently utilized in the generation of the rooftop model from urban imagery. We carry out the experiments on our hybrid stereo matching scheme. We generate synthetic images by photo-realistic simulation on Avenches data set of Ascona aerial images. Experimental results indicate that the extracted 3D line segments have an average error of 0.5m and verify our proposed scheme. In order to apply our method to the generation of 3D model in urban imagery, we carry out Preliminary experiments for rooftop generation. Since occlusions are occurred around the outlines of buildings, we experimentally suggested multi-image hybrid stereo system, based on the fusion of 3D line segments. In terms of the simple domain-specific 3D grouping scheme, we notice that an accurate 3D rooftop model can be generated. In this context, we expect that an extended 3D grouping scheme using our hybrid technique can be efficiently applied to the construction of 3D models with more general types of building rooftops.

• 한국지리정보학회지
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• 제13권3호
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• pp.42-52
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• 2010

본 연구는 항공디지털 스테레오영상으로부터 사진측량기법을 적용하여 한반도 서해안 갯벌중 하나인 제부도 갯벌에 대해 퇴적 침식의 변화를 탐지하는데 기초자료가 될 수 있는 DEM을 제작하였다. 이를 위해, 상호표정에 의한 에피폴라 선을 추출하였으며, 반사도 및 질감 등을 바탕으로 갯벌표면 분류영상을 제작하여, 각 표면 특성별 적합한 매칭사이즈를 선정하고, 이로부터 영역기반매칭을 수행하였다. 결과적으로, 갯벌과 같이 고도의 변화가 미묘한 지역에서는 제안방법으로 제작한 DEM이 고정된 매칭사이즈로 제작한 DEM과 기존 상용 S/W에 의한 DEM 보다 더욱 세밀한 높낮이 변화를 보여주었다.

• Journal of Information Processing Systems
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• 제13권2호
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• pp.256-267
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• 2017

An active research area in computer vision, stereo matching is aimed at obtaining three-dimensional (3D) information from a stereo image pair captured by a stereo camera. To extract accurate 3D information, a number of studies have examined stereo matching algorithms that employ adaptive support weight. Among them, the adaptive census transform (ACT) algorithm has yielded a relatively strong matching capability. The drawbacks of the ACT, however, are that it produces low matching accuracy at the border of an object and is vulnerable to noise. To mitigate these drawbacks, this paper proposes and analyzes the features of an improved stereo matching algorithm that not only enhances matching accuracy but also is also robust to noise. The proposed algorithm, based on the ACT, adopts the truncated absolute difference and the multiple sparse windows method. The experimental results show that compared to the ACT, the proposed algorithm reduces the average error rate of depth maps on Middlebury dataset images by as much as 2% and that is has a strong robustness to noise.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.306-309
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• 1996

This paper presents a method of landmark recognition in indoor environments using a neural-network for an autonomous mobile robot. In order to adapt to image deformation of a landmark resulted from variations of view-points and distances, a multi-labeled template matching(MLTM) method and a dynamic area search method(DASM) are proposed. The MLTM is. used for matching an image template with deformed real images and the DASM is proposed to detect correct feature points among incorrect feature points. Finally a feed-forward neural-network using back-propagation algorithm is adopted for recognizing the landmark.

• 한국ITS학회 논문지
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• 제21권2호
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• pp.132-151
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• 2022

차량 측위 기술은 차량의 정확한 위치 정보를 제공한다는 점에서 자율주행을 위한 핵심 기술 중 하나로 평가되고 있다. 이미지 기반의 측위 기술은 위치 정보를 효율적으로 제공할 수 있을 것으로 판단되어 다양한 관련 연구가 진행되고 있다. 하지만, 기존 특징점 또는 차선 정보를 이용한 이미지 기반 측위 방법론은 도로 및 운행 환경에 측위 정확도가 큰 영향을 받을 수 있다는 한계가 있다. 선분 매칭은 특징점에 비하여 텍스쳐 반복에 강건하고 주변 환경 전체에서 추출된 선분을 활용하기 때문에 기존 방법론의 단점을 해결할 수 있다. 하지만, 차량 운행환경을 대상으로 한 선분 매칭 방법론을 다루는 연구는 거의 진행된 바 없다. 따라서 본 연구에서는 정확한 차량 측위 지원을 위한 선분 매칭 프레임워크를 제안한다. 또한 도로 주행 환경에서의 알고리즘 성능 비교 분석을 통하여 최적 선분 매칭 알고리즘을 결정하였다. 최종적으로 제안된 프레임워크는 선분 추출, 병합, 중첩 영역 탐지 및 MSLD 기반 선분 매칭의 4단계로 구성되었다. 제안된 프레임워크는 차량의 속도, 운행 방식, 주변 환경에 상관없이 차량 측위에 충분한 수준의 선분 매칭을 안정적으로 수행하였다.

• 한국측량학회지
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• 제35권2호
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• pp.75-80
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• 2017

Recently, there has been growing interest in spatial data that combines information and communication technology with smart cities. The high-precision LiDAR (Light Dectection and Ranging) equipment is mainly used to collect three-dimensional spatial data, and the acquired data is also used to model geographic features and to manage plant construction and cultural heritages which require precision. The LiDAR equipment can collect precise data, but also has limitations because they are expensive and take long time to collect data. On the other hand, in the field of computer vision, research is being conducted on the methods of acquiring image data and performing 3D reconstruction based on image data without expensive equipment. Thus, precise 3D spatial data can be constructed efficiently by collecting and processing image data using CCTVs which are installed as infrastructure facilities in smart cities. However, this method can have an accuracy problem compared to the existing equipment. In this study, experiments were conducted and the results were analyzed to increase the number of extracted matching points by applying the feature-based method and the area-based method in order to improve the precision of 3D spatial data built with image data acquired from stereo CCTVs. For techniques to extract matching points, SIFT algorithm and PATCH algorithm were used. If precise 3D reconstruction is possible using the image data from stereo CCTVs, it will be possible to collect 3D spatial data with low-cost equipment and to collect and build data in real time because image data can be easily acquired through the Web from smart-phones and drones.

• Journal of Korean Dental Science
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• 제13권1호
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• pp.28-34
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• 2020

Purpose: The purpose of this study was to investigate the influence of different implant computer software on the accuracy of image registration between radiographic and optical scan data. Materials and Methods: Cone-beam computed tomography and optical scan data of a partially edentulous jaw were collected and transferred to three different computer softwares: Blue Sky Plan (Blue Sky Bio), Implant Studio (3M Shape), and Geomagic DesignX (3D systems). In each software, the two image sets were aligned using a point-based automatic image registration algorithm. Image matching error was evaluated by measuring the linear discrepancies between the two images at the anterior and posterior area in the direction of the x-, y-, and z-axes. Kruskal-Wallis test and a post hoc Mann-Whitney U-test with Bonferroni correction were used for statistical analyses. The significance level was set at 0.05. Result: Overall discrepancy values ranged from 0.08 to 0.30 ㎛. The image registration accuracy among the software was significantly different in the x- and z-axes (P=0.009 and <0.001, respectively), but not different in the y-axis (P=0.064). Conclusion: The image registration accuracy performed by a point-based automatic image matching could be different depending on the computer software used.

• 대한원격탐사학회지
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• 제37권5_1호
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• pp.1135-1147
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• 2021

고해상도 위성영상의 기하보정을 위해 촬영 당시의 위성 센서와 지표면과의 기하학적 관계를 복원하는 센서모델링 과정이 필요하다. 이를 위해 일반적으로 고해상도 위성은 RPC (Rational Polynomial Coefficient) 정보를 제공하고 있지만, 제공 RPC는 위성 센서의 위치와 자세 등에 의해 발생하는 기하왜곡을 포함하고 있다. 이러한 RPC 오차를 보정하기 위해 일반적으로 지상기준점(Ground Control Points)을 활용한다. 지상기준점을 수집하는 대표적인 방법으로 현장 측량을 통해 지상좌표를 취득하지만, 이는 위성영상의 품질이나 촬영 시기에 따른 토지피복의 변화, 기복변위 등으로 위성영상 내에서 지상기준점을 판독하기에 어려운 문제가 있다. 이에 최근에는 다양한 센서로부터 취득된 영상지도를 참조자료로 이용하여, 영상정합 기법을 통해 지상기준점 수집을 자동화할 수 있다. 본 연구에서는 무인항공기 영상을 활용하여 추출된 정합점을 통해 KOMPSAT-3A 위성영상의 RPC를 보정하고자 한다. 무인항공기 영상과 KOMPSAT-3A 위성영상의 정합점 추출을 위한 전처리 방법을 제안하고, 대표적인 특징기반 정합기법(Feature-based matching method)과 영역기반 정합기법(Area-based matching method)인 SURF (Speeded-Up Robust Features)와 위상상관(Phase Correlation) 기법을 각각 적용하여 추출된 정합점의 특성을 비교하였다. 각 기법을 통해 추출된 정합점을 활용하여 RPC 보정계수를 산출한 후, GNSS (Global Navigation Satellite System) 측량을 통해 직접 취득한 검사점에 적용하여 KOMPSAT-3A의 기하품질을 향상하였다. 제안기법의 성능 및 활용성 검증을 위해 GCP를 이용하여 보정한 결과와 비교하여 분석하였다. GCP 기반 보정 방법은 제공 RPC보다 Sample은 2.14 pixel, Line은 5.43 pixel 만큼 개선된 보정 정확도를 보였다. 그리고 SURF와 위상상관 기법을 활용한 제안기법은 제공 RPC보다 각각 Sample은 0.83 pixel, 1.49 pixel만큼 보정되었으며, Line은 4.81 pixel, 5.19 pixel만큼 개선되었다. 이를 통해 GCP 기반 위성영상 RPC 보정 방법의 대안으로 무인항공기 영상이 활용될 수 있음을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.243-243
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• 2000

This paper introduces a visual inspecting and monitoring system based on an image processing technique. We propose an image processing method for analyzing landslide movement in real time. The method adopts Laplacian of Gaussian operator to extract linear features for the captured images and uses a linear matching algorithm to distinguish the matching error for those features. When the algorithm is processed, motion parameters such as displacement area and its direction are computed. Once movement is recognized, displacements are estimated graphically with statistical amount in the image plane. The simulation results are shown us to verify the effectiveness of the developed method.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2011년도 제43차 동계학술발표논문집 19권1호
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• pp.59-62
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• 2011

A new method is proposed for stereo vision where solution to disparity map is presented in terms of Line constraint and Reliability space -- the first constraint proposes a progressive framework for stereo matching which applies local area pixel-values from corresponding lines in the left and right image pairs. The second states that reliability space based on corresponding points records the disparity and then we are able to apply the median filter in order to reduce the noises which occur in the process. A coarse to fine result is presented after the median filtering, which improves the final result qualitatively. Experiment is evaluated by rectified stereo matching images pairs from Middlebury datasets and has proved that those two adopted strategies yield good matching quantitative results in terms of fast running speed.