• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1133-1138
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• 2023

This study analyzed the relationship between image parameters and specific absorption rate (SAR) in various sequence environments to optimize SAR. For this purpose, image parameters were adjusted for T2, T1, STIR, T1 FLAIR, and T2 FLAIR sequences in a 3.0T MRI, and the whole body (WB) SAR and head SAR calculated by the device were measured. Then, the SAR was evaluated by adjusting the number of images and the flip angle (FA) of the refocusing RF. As a result, SAR increased as the number of image increased in all sequences. T1 and T1 FLAIR had correlation coefficients (r) of 0.876, 0.876 (WB SAR, head SAR), 0.867, 0.867 (WB SAR, head SAR), respectively, and STIR had the highest correlation with 0.898 and 0.899 (WB SAR, head SAR). showed (p<0.05). When applied by increasing the refocusing FA, WB SAR and head SAR increased overall in all sequences. The T1 and T2 sequences showed high correlation with correlation coefficients (r) of 0.897, 0.898 (WB SAR, head SAR) and 0.914, 0.915 (WB SAR, head SAR), respectively, while the sequences to which the inversion recovery technique was applied had relatively low FA, showed less sensitivity to increase. Therefore, in a sequence with a relatively low TR, minimizing the number of image and applying the fast spin echo to reduce the refocusing FA in a sequence with a high duty cycle are effective in reducing SAR.

• Korean Journal of Remote Sensing
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• v.23 no.4
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• pp.237-245
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• 2007

GB-SAR (Ground-Based Synthetic Aperture Radar) system is an imaging radar that obtains high resolution 2-D image through a synthetic aperture effect from the accurate linear-motion control of antenna on the ground. The highly versatile system configurations and accurate repeatability of GB-SAR operation allow one to accurately monitor the stability of surface scatterers with millimeter accuracy by SAR interferometry. In this paper we introduce the development of a GB-SAR system and show the possibilities of SAR polarimetry and interferometry such as DInSAR, Cross-Track InSAR, Delta-f InSAR, and PSInSAR.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.55-67
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• 2022

In this paper, fundamentals and recent development of the interferometric synthetic aperture radar, known as InSAR, technique for measuring ground deformation through satellite image analysis are presented together with case histories illustrating its applicability to urban ground deformation monitoring. A study area in Korea was selected and processed based on the muti-temporal time series InSAR analysis, namely SBAS (Small Baseline Subset)-InSAR and PS (Persistent Scatterers)-InSAR using Sentinel-1A SAR images acquired from the year 2014 onward available from European Space Agency Copernicus Program. The ground settlement of the study area for the temporal window of 2014-2022 was evaluated from the viewpoint of the applicability of the InSAR technique for urban infrastructure settlement monitoring. The results indicated that the InSAR technique can reasonably monitor long-term settlement of the study area in millimetric scale, and that the time series InSAR technique can effectively measure ground settlement that occurs over a long period of time as the SAR satellite provides images of the Korean Peninsula at regular time intervals while orbiting the earth. It is expected that the InSAR technique based on higher resolution SAR images with small temporal baseline can be a viable alternative to the traditional ground borne monitoring method for ground deformation monitoring in the 4^th industrial era.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.181-190
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• 2011

Since the radar satellite missions such as TerraSAR-X and COSMO-SkyMed were launched in 2007, the spatial resolution of spaceborne SAR(Synthetic Aperture Radar) images reaches about 1 meter at spotlight mode. In 2011, the first Korean SAR satellite, KOMPSAT-5, will be launched, operating at X-band with the highest spatial resolution of 1 m as well. The improved spatial resolution of state-of-the-art SAR sensor suggests expanding InSAR(Interferometric SAR) analysis in urban monitoring. By the way, the shadow and layover phenomena are more prominent in urban areas due to building structure because of inherent side-looking geometry of SAR system. Up to date the most conventional algorithms do not consider the return signals at the frontage of building during InSAR phase and SAR intensity simulation. In this study the new algorithm introducing multi-scattering in layover region is proposed for phase and intensity simulation, which is utilized a precise LIDAR DSM(Digital Surface Model) in urban areas. The InSAR phases simulated by the proposed method are compared with TerraSAR-X spotlight data. As a result, both InSAR phases are well matched, even in layover areas. This study will be applied to urban monitoring using high resolution SAR data, in terms of change detection and displacement monitoring at the scale of building unit.

• The Journal of the Korea Contents Association
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• v.7 no.3
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• pp.176-186
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• 2007

As SAR data have the strong point that is not influenced by weather or light amount in comparison with optical sensor data, they are highly useful for temporary analysis and can be collected in time of unforeseen circumstances like disaster. This study is to extract DEM from L-band data of JERS-1 SAR imagery using InSAR and DInSAR processing techniques. As a result of analyzing the extracted coherence and interferogram images, it was shown that the DInSAR 3-pass method produces more suitable coherence values than the InSAR method. The accuracies of DEM extracted from the SAR data were evaluated by employing the DEM derived from the digital topographic maps of 1:5000 scale as reference data. And it was ascertained that baselines between antenna locations largely affect the accuracy of extracted DEM.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.4
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• pp.109-116
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• 2013

To extract the 3D geometric information from SAR(Synthetic Aperture Radar) images, two different techniques, interferometric SAR and radargrammetry, have been widely used. InSAR is most widely used for the generation of precise DEM(Digital Elevation Model) until now. But, Interferometric SAR requires severe temporal correlation over areas covered with vegetation and high relief areas. Because radargrammetry is less sensible to temporal correlation, it can provide better results than interferometric SAR in certain, especially X-band SAR. In this paper, we assess the properties of DEMs generated by radargrammetry using stereo C-band RADARSAT-1 images and X-band TerraSAR-X images.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.29-33
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• 2000

The classical image reconstruction for stripmap SAR is based on the Fresnel approximation which utilizes deramping or chirp deconvolution in the synthetic aperture(slow-time) domain. Another approach in formulating stripmap SAR processing and imaging is based on the SAR wavefront reconsturction theory, and analysis of the SAR signal in the slow-time via the spherical wave Fourier decomposition of the radar radiation pattern. In this paper, we compare the Fresnel approximation and the wavefrong reconstruction methods using simulated stripmap SAR dada.

• Korean Journal of Remote Sensing
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• v.21 no.6
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• pp.483-491
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• 2005

SAR signal processing technique has been considered a crucial technical part in order to generate an image from radar signal data and ADD (Agency for Defense Development) has focused on this area for years to develope our own SAR Processor for various SAR systems (Radarsat, ERS, KOMSAR). In this paper, we investigated major techniques related to generation of SAR images and developed ASPR (ADD SAR Processor for Radarsat) practically using the commercial Radarsat-1 radar signal data (RAW). We demonstrated the performance of the ASPR in comparison with the image generated by MDA and Vexcel's SAR Processor (FOCUS).

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.2
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• pp.147-156
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• 2005

SAR interferometry (InSAR) is a technique to generate 3-Dimentional spatial information using complex data pairs observed by antennas at different locations. In case of the Two-pass differential SAR inteferometry (DInSAR), the topographic phase signature can be separated from the contribution of surface deformation in the interferometric phase. In this study, InSAR and DInSAR were implemented with ERS- l/2 tandem pair to produce DEM. The accuracy of the Resulting DEMs was analyzed.

• 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.