• Journal of the Korean Geophysical Society
• /
• v.9 no.1
• /
• pp.1-6
• /
• 2006

To remove ringing and increase vertical resolution of GRP data, signature deconvolution was applied to GPR data obtained using a 100 MHz antenna in the Soyang Lake. The signature was extracted through stacking reflection signals from the lake bottom. Results of this deterministic deconvolution was compared with those from the conventional Wienner method. Due to increased vertical resolution, both deconvolution methods are able to resolve three or more layers in an apparent single layer on the input data. However, identification of reflection boundaries from ringing is not easy due to poor definition in the output data of the Wienner filter. On the contrary, the signature deconvolution greatly enhances both vertical resolution and definition of reflection boundaries, showing detailed internal stratigraphic features of the three sedimentary layers. Since extraction of signature at various depths is possible, this deconvolution method can be appled effectively to unstationary GPR data.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2006.06a
• /
• pp.265-270
• /
• 2006

High-frequency electromagnetic (EM) wave propagation phenomena associated with borehole ground-penetrating radar (GPR) surveys are complex. To improve the understanding of governing physical processes, we present a finite-difference time-domain solution of Maxwell's equations in cylindrical coordinates. This approach allows us to model the full EM wavefield associated with borehole GPR surveys. The algorithm can be easily implemented perfectly matched layers for absorbing boundaries, frequency-dependent media, and finite-length transmitter antenna.

• 한국정보통신설비학회:학술대회논문집
• /
• 2003.08a
• /
• pp.382-384
• /
• 2003

지하 30m 암반에 건설된 통신구 터널의 안전성을 검토하기 위하여 콘크리트 라이닝 두께를 지중레이다(Ground Penetrating Radar)와 충격반향기법(Impact-Echo Method)으로 추정하였다. 지중레이다에 의한 콘크리트 라이닝 단면의 연속적인 화상으로부터 라이닝 두께의 상대적인 변화를 파악하였으며, 라이닝 두께가 얇은 구간은 충격반향 기법에 의해 일정 간격으로 두께를 추정하였다. 터널 천장의 라이닝 두께는 31.85cm, 좌측 및 우측 측벽부의 라이닝 두께는 각각 32.45cm. 32.97cm로서 설계 값인 30cm와 비교적 잘 일치하는 것으로 파악되었다. 지중레이다와 충격반향기법을 조합한 본 방법은 터널 라이닝 콘크리트 두께를 추정하는데 있어서 매우 효율적이고 신뢰성 있는 방법으로 분석되었다.

• Geophysics and Geophysical Exploration
• /
• v.10 no.1
• /
• pp.69-76
• /
• 2007

High-frequency electromagnetic (EM) wave propagation associated with borehole ground-penetrating radar (GPR) is a complicated phenomenon. To improve the understanding of the governing physical processes, we employ a finite-difference time-domain solution of Maxwell's equations in cylindrical coordinates. This approach allows us to model the full EM wavefield associated with crosshole GPR surveys. Furthermore, the use of cylindrical coordinates is computationally efficient, correctly emulates the three-dimensional geometrical spreading characteristics of the wavefield, and is an effective way to discretise explicitly small-diameter boreholes. Numerical experiments show that the existence of a water-filled borehole can give rise to a strong waveguide effect which affects the transmitted waveform, and that excitation of this waveguide effect depends on the diameter of the borehole and the length of the antenna.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.10a
• /
• pp.445-447
• /
• 2014

최근에 전자문화지도에 대한 관심이 늘어나면서 다양한 주제를 기반으로 한 전자문화지도들이 연구 및 개발되고 있는 추세이다. 그러나 기존의 전자문화지도들은 대부분 단일 주제로 제작되므로 주제들 간의 연관성 분석이 어렵고, 전자문화지도들이 서로 연계되어 있지 않아 다양한 관점을 기반으로 한 활용이 미흡한 문제점이 있다. 본 논문에서는 이러한 문제점을 해결하기 위하여 하나의 전자문화지도에 레이어 기능을 활용하여 다양한 주제들을 표현하는 방안을 제시한다. 또한, 이를 기반으로 전자문화지도에서의 주제별 중첩 기능을 활용하여 주제들 간의 연계 관계를 효율적으로 파악하고 다양한 주제들의 연관 관계를 통해 새로운 지식을 도출해 낼 수 있는 활용 방안을 제시하고자 한다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.4
• /
• pp.322-328
• /
• 2000

In this paper, we were investigated the detectability on various specimen in self-designed test field using the GPR system with three antenna elements. The GPR system was constantly radiated 730MHz frequency. To examine the detectability on various condition, the test were experimented using different materials, size and buried depth. As an adjusted wave-propagation velocity, the location of hyperbolic curve pattern were displayed B-scan CRT. And the pattern was exactly positioned when it was compared to the real buried-depth. Therefore, we can confirm similarity between the wave-propagation velocity and previous results.

• Tunnel and Underground Space
• /
• v.27 no.6
• /
• pp.387-392
• /
• 2017

Recently, road cave-ins, also referred to as ground sinking, have become a problem in urban environments. Public utility facilities such as sewage pipelines, communications pipes, gas pipes, power cables, and other types of underground structures are installed below the roads. It was reported that cave-ins are caused by the aging and lack of proper maintenance of underground facilities, as well as by construction problems. A road cave-in is first initiated by the formation of cavities typically induced by the breakage of underground pipelines. The cavities then grow and reach the base of the pavement. The traffic load applied at the surface of the roads causes an abrupt plastic deformation. This type of accident can be considered as a type of disaster. A road cave-in can threaten both human safety and the economy. It may even result in the loss of human life. In the city of Seoul, efforts to prevent damage before cave-ins occur have been prioritized, through a method of discovering and repairing joints through the 3D GPR survey.

• Geophysics and Geophysical Exploration
• /
• v.9 no.4
• /
• pp.304-315
• /
• 2006

We have examined the applicability of f-k analysis to the GPR direct wave measurement for water content to characterize vadose zone condition. When the vadose zone consists of a dry surface layer over wet substratum, we obtained f-k spectra where most of the energy is bounded by the air and dry soil velocities. In this case, dry soil velocity was successfully estimated by using high frequency data. On the other hands, when wet soil overlies dry substratum, the f-k spectra show a contrasting response where most of the energy travels with the velocity bounded by dry and wet soil velocities. In this case, the radar waves are trapped and guided within wet soil layer, exhibiting velocity dispersion. By adopting modal propagation theory, we could formulae a simple inversion code to find two layer's dielectric constants as well as layer thickness. By inverting the velocity dispersion curve obtained from f-k spectra of synthetic modeling data, we could obtain good estimates of dielectric constants of each layer as well as first layer thickness. Moreover, we could obtain more accurate results by including the higher mode data. We expect this method will be useful to get the quantitative property of real subsurface when the field condition is similar.