• 융합신호처리학회논문지
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• 제13권1호
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• pp.12-18
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• 2012

스테레오 대응성은 스테레오 비전에서 중요한 문제이다. 본 논문은 다해상도 기법과 AD-Census를 이용한 유전 알고리즘 기반의 스테레오 정합 기법을 제안한다. 정합 환경을 최적화 문제로 간주하여 유전 알고리즘으로 변위를 탐색한다. 그리고 에지 픽셀을 이용한 적응적 염색체 구조와 교배 방식을 적용한다. 비용함수는 스테레오 정합에서 주로 고려할 수 있는 제약 조건으로 구성하였고, 변위오차를 줄이기 위해 AD-Census 척도를 사용하였다. 처리의 효율을 높이기 위해 영상 피라미드 방법을 적용하여 최저해상도에서 최초 변위 도를 계산한다. 그리고 최초 변위도는 다음 해상도 단계로 전파되어, 보간된 후 지역 특징 벡터를 이용하여 정제를 수행한다. 실험을 통해 제안한 방법이 다른 유전 알고리즘 기반 기법들에 비해 변위 탐색 시간을 감소시킬 뿐만 아니라 정합의 타당성을 보증함을 확인하고자 한다.

• 한국측량학회지
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• 제36권5호
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• pp.355-369
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• 2018

LiDAR (Light Detection And Ranging) strip adjustment is process to improve geo-referencing of the ALS (Airborne Laser Scanner) strips that leads to seamless LiDAR data. Multiple strips are required to collect data over the large areas, thus the strips are overlapped in order to ensure data continuity. The LSA (LiDAR Strip Adjustment) consists of identifying corresponding features and minimizing discrepancies in the overlapping strips. The corresponding features are utilized as control features to estimate transformation parameters. This paper applied SURF (Speeded Up Robust Feature) to identify corresponding features. To improve determination of the corresponding feature, false matching points were removed by applying three schemes: (1) minimizing distance of the SURF feature vectors, (2) selecting reliable matching feature with high cross-correlation, and (3) reflecting geometric characteristics of the matching pattern. In the strip adjustment procedure, corresponding points having large residuals were removed iteratively that could achieve improvement of accuracy of the LSA eventually. Only a few iterations were required to reach reasonably high accuracy. The experiments with simulated and real data show that the proposed method is practical and effective to airborne LSA. At least 80 % accuracy improvement was achieved in terms of RMSE (Root Mean Square Error) after applying the proposed schemes.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.385-388
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• 2013

본 논문에서는 MPEG-7의 EHD(Edge Histogram Descriptor)를 이용한 이미지 매칭기법의 취약점을 보이고 이미지 정규화를 이용해 이를 개선하는 방법을 제안한다. EHD 알고리즘은 edge의 기울기 분포를 수집하여 같은 분포를 가지는 이미지를 매칭하는 기법에 사용한다. 하지만 EHD는 매칭하고자 하는 객체의 회전과 왜곡의 변화에 민감하여 오인식률이 높다. 따라서 이미지를 정규화 하여 매칭하고자 하는 이미지 내의 객체의 edge 정보를 보다 정확하게 추출하여 매칭 성능을 개선한다. 실험을 통해 왜곡과 회전으로 정규화한 EHD 알고리즘을 비교 및 분석하여 기존의 방법에 비해 크기와 회전의 변화에 강인함을 보인다.

• 한국측량학회지
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• 제37권5호
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• pp.331-341
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• 2019

With the popularity of sensor-rich environments, smartphones have become one of the major platforms for obtaining and sharing information. Since it is difficult to utilize GNSS (Global Navigation Satellite System) inside the area with many buildings, the localization of smartphone in this case is considered as a challenging task. To resolve problem of localization using smartphone a four step image-based localization method and procedure is proposed. To improve the localization accuracy of smartphone datasets, MMS (Mobile Mapping System) and Google Street View were utilized. In our approach first, the searching for candidate matching image is performed by the query image of smartphone's using GNSS observation. Second, the SURF (Speed-Up Robust Features) image matching between the smartphone image and reference dataset is done and the wrong matching points are eliminated. Third, the geometric transformation is performed using the matching points with 2D affine transformation. Finally, the smartphone location and attitude estimation are done by PnP (Perspective-n-Point) algorithm. The location of smartphone GNSS observation is improved from the original 10.204m to a mean error of 3.575m. The attitude estimation is lower than 25 degrees from the 92.4% of the adjsuted images with an average of 5.1973 degrees.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1343-1358
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• 2020

In the stagewise arithmetic orthogonal matching pursuit algorithm, the weak threshold used in sparsity estimation is determined via maximum iterations. Different maximum iterations correspond to different thresholds and affect the performance of the algorithm. To solve this problem, we propose an improved variable weak threshold based on the stagewise arithmetic orthogonal matching pursuit algorithm. Our proposed algorithm uses the residual error value to control the weak threshold. When the residual value decreases, the threshold value continuously increases, so that the atoms contained in the atomic set are closer to the real sparsity value, making it possible to improve the reconstruction accuracy. In addition, we improved the generalized Jaccard coefficient in order to replace the inner product method that is used in the stagewise arithmetic orthogonal matching pursuit algorithm. Our proposed algorithm uses the covariance to replace the joint expectation for two variables based on the generalized Jaccard coefficient. The improved generalized Jaccard coefficient can be used to generate a more accurate calculation of the correlation between the measurement matrixes. In addition, the residual is more accurate, which can reduce the possibility of selecting the wrong atoms. We demonstrate using simulations that the proposed algorithm produces a better reconstruction result in the reconstruction of a one-dimensional signal and two-dimensional image signal.

• 대한원격탐사학회지
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• 제38권1호
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• pp.33-43
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• 2022

This study presents a method to restore an optical satellite image with distortion and occlusion due to fog, haze, and clouds to one that minimizes degradation factors by referring to the same type of peripheral image. Specifically, the time and cost of re-photographing were reduced by partially occluding a region. To maintain the original image's pixel value as much as possible and to maintain restored and unrestored area continuity, a simulation restoration technique modified with the Cycle Generative Adversarial Network (CycleGAN) method was developed. The accuracy of the simulated image was analyzed by comparing CycleGAN and histogram matching, as well as the pixel value distribution, with the original image. The results show that for Site 1 (out of three sites), the root mean square error and R² of CycleGAN were 169.36 and 0.9917, respectively, showing lower errors than those for histogram matching (170.43 and 0.9896, respectively). Further, comparison of the mean and standard deviation values of images simulated by CycleGAN and histogram matching with the ground truth pixel values confirmed the CycleGAN methodology as being closer to the ground truth value. Even for the histogram distribution of the simulated images, CycleGAN was closer to the ground truth than histogram matching.

• 전자공학회논문지
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• 제52권1호
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• pp.89-101
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• 2015

본 논문에서는 비냉각방식 적외선 스테레오 카메라 시스템을 이용하여 고속으로 이동하는 고온의 소형 물체의 3차원 위치를 추정함에 있어서 무작위로 추정되는 그 위치를 확률 모델로 표현하는 방법을 제안한다. 본 논문에서 제안하는 확률적 위치 모델은 디지털 영상으로 인한 픽셀위치의 오차(pixel position error)와 비냉각식 적외선 카메라에서 영상을 취득하는 순간의 차이에 의한 지터오차(jitter error)로부터 유도되는데, 두 가지 오차를 결합한 통합 오차확률모델을 수학적으로 제시하고 실험을 통하여 그 효용성을 보여준다. 우선 본 논문에서 고안한 적외선 카메라의 지터 측정기를 이용하여 적외선 카메라에서 발생하는 타이밍 지터를 통계적으로 관찰하여 확률모델을 설정한다. 또한 디지털 영상의 스테레오 정합 과정에서 발생하는 픽셀 오차에 의하여 정확도가 떨어지는 측정거리를 확률모델로 정의한다. 실험 측정 결과, 지터는 가우시안 확률분포로 모델링하는 것이 가능하며, 픽셀오차는 균일 확률분포로 모델링된다. 이 두 가지 확률분포를 갖는 오차는 상호 독립으로서 선형 결합되는데, 전체 오차에 대한 확률분포는 지터오차 변수의 확률분포와 픽셀위치오차 변수의 확률분포를 컨볼루션함으로써 유도된다. 실제 고속 이동체에 대하여 정밀한 3차원 궤적측정기와 자체 구현한 적외선 스테레오 카메라 시스템을 이용하여 제안한 확률모델을 3차원 위치추적 실험에 적용한 결과 95% 신뢰도 구간에서 물체의 위치를 추정하는 것을 확인하였다. 즉, 물체의 위치를 정확하게 측정하는 것은 이론적으로는 불가능하며, 확률모델을 통하여 물체의 위치를 표현하는 것이 타당함을 확인할 수 있다. 본 논문에서 제안한 확률모델은 적외선 스테레오 카메라를 이용한 거리측정에서 부정확함을 확률적으로 모델링하여 위치정보에 대한 불확실성을 보정해주며, 특히 적외선 스테레오 카메라를 이용한 고속 물체의 위치추적 및 거리측정에서 이론적, 실험적 토대를 제공할 것으로 기대된다.

• 제어로봇시스템학회논문지
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• 제7권11호
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• pp.953-957
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• 2001

This paper is concerned with a transfer alignment method for the SDINS under ship motions. Major error sources of transfer alignment are data transfer time-delay, lever-arm velocity and ship body flexure. Specifically, to reduce alignment errors induced by measurement time-delay effects, the error compensation method through delay state augmentation is suggested. A linearized error model for the velocity and attitude matching transfer alignment system is first derived by linearizing the nonliner measurement equation with respect to its time delay and augmenting the delay state into the conventional linear state equations. And then it is shown via observability analysis and computer simulations that the delay state can be estimated and compensated during ship motions resulting in considerably less alignment errors.

• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.161-166
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• 2014

An accurate gain-of-two amplifier, which successfully reduces the capacitor mismatch error is proposed. This amplifier has similar circuit complexity and linearity improvement to the capacitor error-averaging technique, but operates with two clock phases just like the conventional pipeline stage. This makes it suitable for high-speed, high-resolution analog-to-digital converters (ADCs). Two ADC architectures employing the proposed accurate gain-of-two amplifier are also presented. The simulation results show that the proposed ADCs can achieve 15-bit linearity with 8-bit capacitor matching.

• 한국기계가공학회지
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• 제3권4호
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• pp.7-12
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• 2004

Inspection and analysis are essential process to determine whether a completed product is in given specification or not. Analysis of products with very complicated shape is difficult to carry out direct comparison between inspected coordinate and designed coordinates. So process called as matching or registrations is needed to solve this problem. By defining error between two coordinates and minimizing the error, registration is done. Registration consists of translation, rotation and scale transformations. Error must be defined to express feature of inspected product. In this paper, registration algorithm is developed to determine pose of sub-frame at assembly with body of automobile by defining error between two coordinates considering geometric feature of sub-frame.