• 한국전자파학회논문지
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• 제11권7호
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• pp.1258-1270
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• 2000

영상 레이다(SAR)는 기상여건에 무관하게 전천후로 광범위한 지역에 대해 고해상도의 영상획득능력이 우수하므로 군용으로는 물론 과학 및 상업용으로 광범위한 활용분야를 가지고 있다. 본 논문에서는 소형 위성 탑재 SAR 시스템의 임부 및 체계 요구조건을 암족하기 위한 주요 설계 변수와 함께 X 밴드 고해상도의 SAR 체계 설계에 관하여 논한다. 그리고, SAR 영상모드 설계 기법을 기술하고 표준 영상모드 설계 결과를 영상성능 관점에서 분석한다. 그리고, 소형 위성 SAR 탑재체 및 설계 지법을 기술하고 표준 영상모드 설계 결과를 영상성능 관점에서 분석한다. 그리고, 소형 위성 SAR 탑제체 및 지상 수신처리의 설계와 주요 성능결과들을 제시한다. 설계된 위성 SAR 시스템은 광역모드에서 고해상도 모드까지 다양한 영상 모드 구현이 가능하며, 소형, 고성능, 저 비용관점에서 효율적인 전천후 영상획득 시스템이다.

• 지질공학
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• 제27권3호
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• pp.305-312
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• 2017

The most effective way to distinguish subsurface interfaces that produce various geophysical responses is through the integration of multiple geophysical methods, with each method detecting both a complementary and unique set of distinct physical properties relating to the subsurface. In this study, shallow seismic reflection (SSR) and ground penetrating radar (GPR) surveys were conducted at the Cheongju-Gadeok site of the Korea National Groundwater Monitoring Network to map the water table, which was measured at 12 m depth during the geophysical surveys. The water table proved to be a good target reflector in both datasets, as the abrupt transition from the overlying unsaturated weathered rock to the underlying saturated weathered rock yielded large acoustic impedance and dielectric constant contrasts. The two datasets were depth converted and integrated into a single section, with the SSR and GPR surveys conducted to ensure subsurface imaging at approximately the same wavelength. The GPR data provided detailed information on the upper ~15 m of the section, whereas the SSR data imaged structures at depths of 10-45 m. The integrated section thus captured the full depth coverage of the sandy clay, water table, weathered rock, soft rock, and hard rock structures, which correlated well with local drillcore and water table observations. Incorporation of these two geophysical datasets yielded a synthetic section that resembled a simplified aquifer model, with the best-fitting seismic velocity, dielectric constant, and porosity of the saturated weathered layer being $v_{seismic}=1000m/s$, ${\varepsilon}_r=16$, and ${\phi}=0.32$, respectively.

• Korean Journal of Geomatics
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• 제3권1호
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• pp.33-41
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• 2003

Every year, several typhoons hit the Korean peninsula and cause severe damage. For the prevention and accurate estimation of these damages, real time or almost real time flood information is essential. Because of weather conditions, images taken by optic sensors or LIDAR are sometimes not appropriate for an accurate estimation of water areas during typhoon. In this case SAR (Synthetic Aperture Radar) images which are independent of weather condition can be useful for the estimation of flood areas. To get detailed information about floods from satellite imagery, accurate classification of water areas is the most important step. A commonly- and widely-used classification methods is the ML(Maximum Likelihood) method which assumes that the distribution of brightness values of the images follows a Gaussian distribution. The distribution of brightness values of the SAR image, however, usually does not follow a Gaussian distribution. For this reason, in this study the ANN (Artificial Neural Networks) method independent of the statistical characteristics of images is applied to the SAR imagery. RADARS A TSAR images are primarily used for extraction of water areas, and DEM (Digital Elevation Model) is used as supplementary data to evaluate the ground undulation effect. Water areas are also extracted from KOMPSAT image achieved by optic sensors for comparison purpose. Both ANN and ML methods are applied to flat and mountainous areas to extract water areas. The estimated areas from satellite imagery are compared with those of manually extracted results. As a result, the ANN classifier performs better than the ML method when only the SAR image was used as input data, except for mountainous areas. When DEM was used as supplementary data for classification of SAR images, there was a 5.64% accuracy improvement for mountainous area, and a similar result of 0.24% accuracy improvement for flat areas using artificial neural networks.

• Journal of Astronomy and Space Sciences
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• 제28권1호
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• pp.55-62
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• 2011

The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.

• 대한원격탐사학회지
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• 제33권1호
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• pp.69-77
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• 2017

S The need for an automated geo-positioning approach for near real-time results and to boost cost-effectiveness has become increasingly urgent. Following this trend, a new approach to automatically compensate for the bias of the rational function model (RFM) was proposed. The core idea of this approach is to remove the bias of RFM only using tie points, which are corrected by matching with the digital elevation model (DEM) without any additional ground control points (GCPs). However, there has to be a additional evaluation according to the quality of DEM because DEM is used as a core element in this approach. To address this issue, this paper compared the quality effects of DEM in the conduct of the this approach using the Shuttle Radar Topographic Mission (SRTM) DEM with the spatial resolution of 90m. and the National Geographic Information Institute (NGII) DEM with the spatial resolution of 5m. One KOMPSAT-2 stereo-pair image acquired at Busan, Korea was used as experimental data. The accuracy was compared to 29 check points acquired by GPS surveying. After bias-compensation using the two DEMs, the Root Mean Square (RMS) errors were less than 6 m in all coordinate components. When SRTM DEM was used, the RMSE vector was about 11.2m. On the other hand, when NGII DEM was used, the RMSE vector was about 7.8 m. The experimental results showed that automated geo-positioning approach can be accomplished more effectively by using NGII DEM with higher resolution than SRTM DEM.

• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.19-34
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• 2015

One of the main causes of a limited use of nondestructive evaluation (NDE) technologies in bridge deck assessment is the speed of data collection and analysis. The paper describes development and implementation of the RABIT (Robotics Assisted Bridge Inspection Tool) for data collection using multiple NDE technologies. The system is designed to characterize three most common deterioration types in concrete bridge decks: rebar corrosion, delamination, and concrete degradation. It implements four NDE technologies: electrical resistivity (ER), impact echo (IE), ground-penetrating radar (GPR), and ultrasonic surface waves (USW) method. The technologies are used in a complementary way to enhance the interpretation. In addition, the system utilizes advanced vision to complement traditional visual inspection. Finally, the RABIT collects data at a significantly higher speed than it is done using traditional NDE equipment. The robotic system is complemented by an advanced data interpretation. The associated platform for the enhanced interpretation of condition assessment in concrete bridge decks utilizes data integration, fusion, and deterioration and defect visualization. This paper concentrates on the validation and field implementation of two NDE technologies. The first one is IE used in the delamination detection and characterization, while the second one is the USW method used in the assessment of concrete quality. The validation of performance of the two methods was conducted on a 9 m long and 3.6 m wide fabricated bridge structure with numerous artificial defects embedded in the deck.

• Spatial Information Research
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• 제22권1호
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• pp.1-7
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• 2014

본 논문은 차량기반 멀티센서 측량시스템 데이터를 활용하여 도로 및 주변 건물에 대한 3차원 지적정보를 효과적으로 구축하기 위한 방안을 제시하고자 하였다. 3차원 지적정보의 구축은 기존의 지적정보와 공간정보의 융합을 의미하며 토지정보와 함께 다양한 공간정보를 효율적으로 등록 관리할 수 있는 입체적 토지관리를 의미한다. 기술적으로 GPS/INS 통합기술로 계산한 지형 지물들의 위치정보, 영상 또는 라이다 스캐너에 의한 형상정보 및 속성정보는 건축물 및 지상의 객체가 포함된 3차원 입체 지적정보를 구축하는데 매우 유용하다는 것을 확인 하였다. 결과적으로 3차원 지적정보 구축을 위한 차량기반 멀티센서 측량시스템의 적용으로 토지정보의 과학화 및 고도화를 이룰 수 있을 것이다.

• 지구물리
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• 제5권3호
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• pp.175-198
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• 2002

그라우팅 효과 확인의 정량적인 기준을 얻기 위하여 지구물리 방법을 활용한 기술들이 적용되었다. 탄성파, 지하레이다, 전기비저항, 전자기 탐사를 포함하는 다양한 지표 및 시추공 지구물리 탐사 방법이 그라우팅 전후에 대해서 균열 암반 시범 지역에서 수행되었다. 비록, 그라우팅 전후의 지구물리 결과에 다소의 차이가 있지만, 지구물리 조사 자료는 본 시범지역에서 현장 기술자들이 그라우팅 효과를 확신할 만한 기준을 제공하기에는 충분하지 못한 것으로 나타났다. 그라우팅 효과에 대한 보다 세밀한 기준 및 조사를 위하여 다fms 현장에서 본 연구는 계속 진행될 계획이다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2004년도 정기총회 및 제6최 특별 심포지움
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• pp.180-189
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• 2004

(반)월성은 세계문화유산으로 등록된 '경주역사유적지구'에 위치한 왕성으로 특유한 반달모양을 하고 있어 유래된 이름이다. 우리의 신라 천년왕조의 역사를 가진 자랑스러운 월성은 오랜 역사만큼이나 그 신비함이 아직까지 간직되어 오고 있다. 따라서 월성의 신비를 그대로 보존하면서 고고학적인 호기심을 충족시킬 수 있도록 GPR(Ground Penetrating Radar)탐사 조사법을 적용하여, 향후 발굴계획이나 고고학적 연구에 과학적이고 체계적인 접근과 현대고고학과 지구물리학의 접목의 전기를 마련하고자 조사를 실시하였다. 탐사면적은 월성 전체면적의 $10\%$에 해당하는 $12,000m^2$로 석빙고 앞 및 그 주변을 탐사하였으며, 그 결과, $8{\times}8m^2$ 크기의 건물 7채와 담장 및 성의 출입시설, 수많은 초석들, 도로(추정), 그리고 직경 35m크기의 연못으로 추정되는 반응들이 확인되었다.

• 자원환경지질
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• 제39권4호
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• pp.427-440
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• 2006

다른 물리탐사법과는 달리, 전자탐사의 실질적인 국내 활용과 연구는 1980년대부터이다. 이렇게 늦게나마 시작하게 된 것은 1970년대 미국 유학한 네 명의 연구자들의 영향이고, 이 들과의 공동연구와 유대는 현재까지 지속되고 있다. 그 동안 국내 연구진이 이룬 성과는 괄목할 만 하다. 이제 우리는 MT와 CSAMT탐사, 지자기수직탐사, 소형루프탐사, VLF탐사, GPR탐사, 시간영역 전자탐사 등 전 분야에 걸쳐 국제 수준의 기술력을 확보하게 되었고 신기술인 고주파수 전자탐사, 시간영역 전자탐사, 역산기법 분야에서 창의 있는 연구 성과를 내고 있다. 활용 분야도 지하자원탐사에서 지반조사, 환경조사, 고고학조사, 구조물 결함조사, 땅굴조사 등으로 엄청나게 확장되었다. 아직도 자료해석이 난삽하기 이를 데 없는 전자탐사법을 한 단계 높일 결정적인 돌파구가 국내 연구진에 의해서 나올 날이 멀지 않을 것이다.