• The Magazine of the IEIE
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• v.41 no.6
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• pp.18-26
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• 2014

신호의 표현과 압축은 밀접하게 연관되어 있다. 만약 매우 효과적인 신호 표현 방식을 찾을 수 있다면 매우 높은 비율로 신호 압축이 가능하다. 또한 효과적인 신호 표현 방식을 통해 우수한 성능과 낮은 복잡도를 갖는 신호 추정 방식을 유도할 수도 있다. 효과적인 신호 표현 방식은 대상 신호 자체의 성질과 관련되어 있다. 영상 신호등 매우 일반적인 신호가 적절한 변환을 통해 산재된 신호(sparse signal)가 될 수 있음을 많은 연구를 통해 볼 수 있다. 이러한 사실이 compressive sensing(CS)의 기반이다. 즉 신호가 어떠한 변환을 통해 산재된 신호로 표현될 수 있다면 매우 적은 수의 샘플로 이러한 신호를 알아낼 수 있다는 것을 Donoho와 Candes 등이 보였고 이것이 가능한 다양한 조건에 등에 대해 연구되었다. CS는 신호 처리에 근본적인 문제인 효과적인 신호 표현 방식에 직접 연관되어 매우 다양한 분야에 적용될 수 있다. 이 논문에서 CS의 기본적인 개념을 소개한 후 CS가 레이더 신호 처리에 어떻게 도움이 될 수 있는지 살펴본다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.3
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• pp.333-338
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• 2014

In this paper, we researched the recent analysis method of RCS prediction for the naval ship and compared the new method with conventional one in respect of the effectiveness to improve a naval ship with low RCS. This paper included the process of analyzing RCS characteristics for naval ship using the numerical method and finding the hotspot by hourglass plot, ISAR image and etc.. Also we introduced the various design methods in order to reduce RCS.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.138-145
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• 2008

In this paper, the waveguide slot array antenna which is capable of wide beam steering and dual polarization is designed for an X band synthetic aperture radar. In order to improve the restriction of beam steering range and to remove the butterfly lobes, a typical waveguide slot array antenna has been modified. To implement dual polarization, rod excited waveguide slot elements and ridge waveguide slot elements are alternately arranged. Location of slots, inclination of rod and offset distance of slots are determined on using array characteristic and conductance constant with radiating power on slots. The designed antenna is manufactured and measured with Near-filed measurement method.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.62-65
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• 2003

We propose an algorithm for almost unsupervised detection of linear structures, in particular, axes in road network and river, as seen in synthetics aperture radar (SAR) images. The first is local step and used to extract linear features from the speckle radar image, which are treated as road segment candidates. We present two local line detectors as well as a method for fusing information from these detectors. The second is global step, we identify the real roads among the segment candidates by defining a Markov random field (MRF) on a set of segments, which introduces contextual knowledge about the shape of road objects.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.221-224
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• 2000

We propose an algorithm for almost unsupervised detection of linear structures, in particular, axes in road network and river, as seen in synthetics aperture radar (SAR) images. The first is local step and used to extract linear features from the speckle radar image, which are treated as road segment candidates. We present two local line detectors as well as a method for fusing information from these detectors. The second is global step, we identify the real roads among the segment candidates by defining a Markov random field (MRF) on a set of segments, which introduces contextual knowledge about the shape of road objects.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.148-148
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• 2017

본 연구에서는 합성개구레이더(Synthetic Aperture Radar, SAR) 인공위성 영상을 활용한 풍수해 피해지역 감지 기법을 제안하고자 한다. SAR 인공위성 자료를 분석하여 풍수해 피해 중 지반의 변화량 및 변화양상 감지를 분석하였다. 연구지역은 울릉도 전역이며, 2016년 8월 30일 제 10호 태풍 라이언록에 의한 피해를 분석하였다. SAR Interferometry(InSAR) 기법을 적용하여 홍수 전, 후의 지반 변화량을 분석하였다. 분석결과의 정확도를 파악하기 위해 분석결과를 실제 피해사례 및 피해 사진 등과 비교, 분석하여 검증을 실시하였다. 검증결과, 정성적인 지반변화 및 변화양상은 판별되었으나, 정량적인 지반변화량 파악은 어려운 것으로 나타났다. 현재 국내지역에 대해 InSAR 기법을 적용하여 홍수 전, 후의 지반변화 감지를 적용해본 사례가 많지 않은 실정이며, 본 연구는 국내지역에 대해 InSAR 기법을 적용하여 풍수해 피해감지를 하였다는 의미가 있다.

• Proceedings of KOSOMES biannual meeting
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• 2008.05a
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• pp.125-127
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• 2008

허베이스피리트호 원유유출 사고는 2007년 12월7일 아침 7시6분경 서해안 만리포 북서쪽 10km 해상에서 크레인을 적재한 1만1800t급 바지선이 정박 중인 흥콩 선적 유조선 허베이 스피리트호(14만6000t급)와 부딪치면서 발생했다. 이와 같은 기름 유출 사고의 경우, 유출 범위를 정확하게 이해하는 것이 중요하다. 여기서는 위 사고 기간에 얻어진 인공위성 자료를 이용하여 기름 유출을 탐지하기 위한 연구결과를 소개한다. 광학과 마이로파영상에 대해 유출 범위의 계산 및 해석 알고리듬에 대한 현재까지의 결과를 소개한다. 광학영상으로는 아리랑 2호 (다목적 실용위성 2호, KOMPSAT II) MSC(Multi Spectral Camera)자료가 사용되었으며, 합성개구레이더로는 ENVISAT ASAR, TerraSAR-X 및 ALOS PALSAR의 자료가 사용되었다.

• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1415-1425
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• 2018

Kompsat-5 is the first Earth Observation Satellite which is equipped with an SAR in Korea. SAR images are generated by receiving signals reflected from an object by microwaves emitted from a SAR antenna. Because the wavelengths of microwaves are longer than the size of particles in the atmosphere, it can penetrate clouds and fog, and high-resolution images can be obtained without distinction between day and night. However, there is no color information in SAR images. To overcome these limitations of SAR images, colorization of SAR images using Cycle GAN, a deep learning model developed for domain translation, was conducted. Training of Cycle GAN is unstable due to the unsupervised learning based on unpaired dataset. Therefore, we proposed MS Cycle GAN applying multi-scale discriminator to solve the training instability of Cycle GAN and to improve the performance of colorization in this paper. To compare colorization performance of MS Cycle GAN and Cycle GAN, generated images by both models were compared qualitatively and quantitatively. Training Cycle GAN with multi-scale discriminator shows the losses of generators and discriminators are significantly reduced compared to the conventional Cycle GAN, and we identified that generated images by MS Cycle GAN are well-matched with the characteristics of regions such as leaves, rivers, and land.

• Korean Journal of Remote Sensing
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• v.39 no.5_3
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• pp.997-1008
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• 2023

Ship detection at sea can be performed in various ways. In particular, satellites can provide wide-area surveillance, and Synthetic Aperture Radar (SAR) imagery can be utilized day and night and in all weather conditions. To propose an efficient ship detection method from SAR images, this study aimed to apply the You Only Look Once Version 5 (YOLOv5) model to Sentinel-1 images and to analyze the difference between individual vs. integrated models and the accuracy characteristics by polarization. YOLOv5s, which has fewer and lighter parameters, and YOLOv5x, which has more parameters but higher accuracy, were used for the performance tests (1) by dividing each polarization into HH, HV, VH, and VV, and (2) by using images from all polarizations. All four experiments showed very similar and high accuracy of 0.977 ≤ AP@0.5 ≤ 0.998. This result suggests that the polarization integration model using lightweight YOLO models can be the most effective in terms of real-time system deployment. 19,582 images were used in this experiment. However, if other SAR images,such as Capella and ICEYE, are included in addition to Sentinel-1 images, a more flexible and accurate model for ship detection can be built.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5D
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• pp.635-644
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• 2009

Image processing technique in the outdoor environment is very sensitive, and it tends to lose a lot of accuracy when it rapidly changes by outdoor environment. Therefore, in order to calculate accurate traffic information using the traffic monitoring system, we must resolve removing shadow in transition time, Distortion by the vehicle headlights at night, noise of rain, snow, and fog, and occlusion. In the research, we developed a system to calibrate the amount of traffic, speed, and time occupancy by using image processing technique in a variety of outdoor environments change. This system were tested under outdoor environments at the Gonjiam test site, which is managed by Korea Institute of Construction Technology (www.kict.re.kr) for testing performance. We evaluated the performance of traffic information, volume counts, speed, and occupancy time, with 4 lanes (2 lanes are upstream and the rests are downstream) from the 16th to 18th December, 2008. The evaluation method performed as based on the standard data is a radar detection compared to calculated data using image processing technique. The System evaluation results showed that the amount of traffic, speed, and time occupancy in period (day, night, sunrise, sunset) are approximately 92-97% accuracy when these data compared to the standard data.