• Journal of the Korean earth science society
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• v.38 no.4
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• pp.251-262
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• 2017

The system of magnetic exploration with a drone flight was constructed and applied to the iron mine site. The magnetic probe system installed on the drone used a sensor as Bartington's fluxgate type magnetometer, Mag639 and the A/D converter to collect magnetic intensity values on the tablet PC. The drone flight control module is a highly expandable Pixhawk with allowing 15 minutes of flight by loading 3kg. Experiments on the magnetic field interference range were performed to remove the erroneous effect from the drone with applying RTK GPS to obtain the magnetic intensity value at the accurate position. The accurate location information enabled to obtain the gradient measurement of magnetic field by measuring twice at different altitudes. Also, by using the terrain information, we could eliminate the terrain effect by setting the flight path to fly along the terrain. These results are in line with the field experiments using the nuclear proton magnetometer G-858 of Geometrics Co., Ltd, which adds to the reliability of the drone based aeromagnetic survey system we constructed.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.219-224
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• 2007

We conducted geophysical surveys to detect antitank mine at Namji-eup, Gyeongsangnam-do which had been installed during Korean war. The surveys consisted of 2 stages, at the first stage we divided the survey area into 7 block and carried out magnetic gradient survey and GEM-3 EM survey sequentially for each block. Hence we verified anomaly areas using an excavator and a metal detector. Most of anomalies were found to be garbages such as trash cans, metallic wastes, and so on. And also, the concrete pipe was found at depth of 1 m, which had not referred in any report of that area. At the second stage, after trenching the covered soil down to 75 cm the same surveys were conducted. We could not find the strong signal to be inferred from a antitank mine, but we pointed out some anomalies to need careful handling because demining is very dangerous work even though there is few possibility that is mine.

• Investigative Magnetic Resonance Imaging
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• v.21 no.4
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• pp.233-241
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• 2017

Purpose: To report on the current practices in breast magnetic resonance imaging (MRI) in Korea. Materials and Methods: We invited the 68 members of the Korean Society of Breast Imaging who were working in hospitals with available breast MRI to participate in a survey on how they performed and interpreted breast MRI. We asked one member from each hospital to respond to the survey. A total of 22 surveys from 22 hospitals were analyzed. Results: Out of 22 hospitals, 13 (59.1%) performed at least 300 breast MRI examinations per year, and 5 out of 22 (22.7%) performed > 1200 per year. Out of 31 machines, 14 (45.2%) machines were 1.5-T scanners and 17 (54.8%) were 3.0-T scanners. All hospitals did contrast-enhanced breast MRI. Full-time breast radiologists supervised the performance and interpreted breast MRI in 19 of 22 (86.4%) of hospitals. All hospitals used BI-RADS for MRI interpretation. For computer-aided detection (CAD), 13 (59.1%) hospitals sometimes or always use it and 9 (40.9%) hospitals did not use CAD. Two (9.1%) and twelve (54.5%) hospitals never and rarely interpreted breast MRI without correlating the mammography or ultrasound, respectively. The majority of respondents rarely (13/21, 61.9%) or never (5/21, 23.8%) interpreted breast MRI performed at an outside facility. Of the hospitals performing contrast-enhanced examinations, 15 of 22 (68.2%) did not perform MRI-guided interventional procedures. Conclusion: Breast MRI is extensively performed in Korea. The indication and practical patterns are diverse. The information from this survey would provide the basis for the development of Korean breast MRI practice guidelines.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.1
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• pp.1-15
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• 1991

This paper is to aim to review the basic theory of geomagnetic survey and analize the field observation data (1980-1989) measured by Korea G S I. The magnetic Chart of Korea is mapped with use of the analized results and the principal scheme about Korea geomagnetic survey is furthermore proposed

• Journal of the Korean earth science society
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• v.23 no.1
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• pp.87-96
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• 2002

Aeromagnetic and gravity data were analyzed to delineate the subsurface structure of the Yeongdong basin and its related fault movement in the Okcheon fold belt. The aeromagnetic data of the total intensity (KIGAM, 1983) were reduced to the pole and three dimensional inverse modeling, which considers topography of the survey area in the modeling process, were carried out. The apparent susceptibility map obtained by three dimensional magnetic inversion, as well as the observed aeromagnetic anomaly itself, show clearly the gross structural trend of the Yeongdong basin in the direction on between $N30^{\circ}E$ and $N45^{\circ}E$. Gravity survey was carried out along the profile, of which the length is about 18.2 km across the basin. Maximum relative Bouguer anomaly is about 7 mgals. Both forward and inverse modeling were also carried out for gravity analysis. The magnetic and gravity results show that the Yeongdong basin is developed by the force which had created the NE-SW trending the magnetic anomalies. The susceptibility contrast around Yeongdong fault is apparent, and the southeastern boundary of the basin is clearly defined. The basement depth of the basin appears to be about 1.1 km beneath the sea level, and the width of the basin is estimated to be 7 km based on the simultaneous analysis of gravity and magnetic profiles. There exists an unconformity between the sedimentary rocks and the gneiss at the southeastern boundary, which is the Yeongdong fault, and granodiorite is intruded at the northwestern boundary of the basin. Our results of gravity and magnetic data analysis support that the Yeongdong basin is a pull-apart basin formed by the left-stepping sinistral strike-slip fault, which formed the Okcheon fold belt.

• Economic and Environmental Geology
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• v.32 no.2
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• pp.177-187
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• 1999

Gravity, magnetic and VLF surveys were conducted to investigat the structural stability and hazards associated with the Ubong landfill in Pohang City, which has been built to dump industrial wastes. In 1994, the collapse of a bank happened in the 6th landfill site due to sudden heavy rain, and a large quantity of waste materials flowed out to the nearby landfill sites, factories and roads. We used $10{\times}10m$ resolution DEM data for gravity reductions. The maximum variation of the terrain effect in the survey area is about 0.5 mgal and the terrain effect is large in the vicinity of bank boundary. The Bouguer gravity anomaly map shows the effect due to the variatino of thickness and type of waste materials. The small negative gravity anomaly increases from the 9th site to the 6th site. The small negative gravity anomaly of the 9th site reflects the relatively shallow dumping depth of average 14.5 m in this site and increased density of waste materials by the repeated stabilization process of soil overlaying. The 6th site is located at the center of the former valley and rainfall and groundwater are expected to flow from south-east to north-west. Therefore, considering the previous accident of mixing waste and bank materials at the north-west boundary of the landfill, there may be some environmental problems of leakage of contaminated water and bank stability. The complex inversion technique using Simulated annealing and Marquardt-Levenberg methods was applied to calculate three-dimensional density distribution from gravity data. In the case of 6th site, it is apparent that the landfill had been dumped in four sectors. However, most part of the 9th site and showed that high magnetic industrial wastes were concentrated in the 6th site. The result of magnetic survey showing low magnetic anomalies along the boundaries of two sites is similar to that of gravity data. The VLF data also reveals four divided sectors in the 6th site, and overall anomaly trend indicates the directio of former valley.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1827-1829
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• 1997

In this paper, measurement and analysis of ELF electric and magnetic fields due to a transmission line have been carried out and the power frequency field strength measuring system is designed. In order to evaluate electric and magnetic fields associated with 60 Hz electric power transmission and distribution lines, the actual survey near a transmission tower has been made and analyzed. It may be inferred from these results that the maximum electric and magnetic fields strength in the vicinity of a line tower do not exceed 3.5[kV/m] and 20[${\mu}T$]. The results of the field measurements agree with limits and guidelines recommended by various authorized international institutes.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.403-416
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• 2006

Magnetic method is rapid, cheap and simple geophysical exploration technique, and has wide range of applications such as resources prospecting, geological structure investigation and even geotechnical and environmental problems. Especially, aeromagnetics gives fundamental and useful geoscientific data fnr not only assessment of potential resources, but also national land planning. Magnetic method, perhaps the oldest geophysical technique, was relatively early introduced into Korea. Documents during Japanese occupation says that magnetic method was used for exploring metallic ore deposits and hot spring, and that a geomagnetic observatory was operated. From mid 1950's, after Korean War, magnetic explorations for natural resources such as metallic ore, uranium, coal, and groundwater were intensively executed for industrialization. Apache aeromagnetic survey project during $1958{\sim}1959$ and its ground follow-up surveys are typical and important cases in those days. Magnetic survey techniques were rapidly advanced during 1970's and 1980's with improvements of instruments, growth of geophysical manpower, and availability of computers. The national aeromagnetic mapping project by KIGAM in 1981 showed the improved technical capability of those days. Decline of mining industry since mid 1980's moved the exploration objects from traditional resources to new ones such as groundwater and geothermal resources, and applications to investigation of geological structure were revived. Recently appeared applications such as natural hazard assessment, and engineering and environmental studies increased the magnetic method's utility in the realm of exploration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.6
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• pp.526-534
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• 2009

The magnetic field of the extremely low frequency that occurs in the substation facilities was surveyed to present ways to broaden understanding of the magnetic field characteristics. We have investigated the level of the magnetic fields in the substation areas and control rooms of 25 substations in the metropolitan area in accordance with the measurement method of IEC CISPR(IEC/TC106 PT 62110). We propose objective and reliable policy approaches such as the electromagnetic field certification system to more accurately understand the property of magnetic field.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.687-697
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• 1998

In spite of increasing public concern about the human exposure to electric and magnetic fields(EMFs), there is little information about the EMF levels in the vicinity of power facilities and of home appliances. To provide such information, a nationwide survey for EMFs near overhead transmission lines has been conducted. The median values of the electric fields and magnetic fields of 153 transmission lines were 0.47 kV/m and 11.6 mG, respectively. The maximum values were 3.16 kV/m and 125 mG. These were low values in comparison with any EMF guidelines or standards of advanced contries. Measurements of the magnetic fields of typical home appliances and daily human exposure records have been also conducted. These magnetic field values were comparable to those of the transmission lines.