• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.140-146
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• 1989

In many situations, radar targets are embedded in a clutter environment and clutter rejection is required. The clutter is unwanted radar echoes and may arise owing to reflections from ground and weather disturbances and statistical properties of the clutter vary with range and azimuth as well as time. That is, adaptive signal processing is required. In this paper, a clutter suppression algorithm based on the clutter whitening filter (WF) and doppler filter bank(DFB) is described which provides improved performance compared with conventional nonadaptive clutter suppression algorithm that is the cascaded moving target indicator (MTI) and (DFB). The clutter whitening filter algorithm is based on the Burg's maximum entropy method.

• Journal of Cadastre & Land InformatiX
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• v.45 no.2
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• pp.131-147
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• 2015

In modern society, as to the underground urban infrastructure facilities(communication electricity water and sewage gas etc.) were contained many risks because of excavating. The exact position of underground facilities and the attribute information should be built in order to prevent accidents. As the result of analyzing the public surveying results from 2004 to 2009, it shows that low detecting rate of water pipeline which is only 52.4%, because the exploration of electromagnetic induction only detect metal pipeline and positioning survey only detect new pipeline before burying. Therefore development and verification of the correct and efficient exploration techniques are needed to improve the detecting rate. In this study, determined based on the location measurement results for the non-metal pipes and metal pipes before burial. It was compared with values that obtained through the ground penetrating radar and electromagnetic induction detecting. As a result, detecting rate of the concrete section showed a 100%, unpaved section showed a 94.7%, asphalt section showed 60%. So it confirmed the applicability of the ground penetrating radar at underground facilities detecting.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.1-7
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• 1999

We investigated the weathering characteristics of On-Yang gneiss by means of geological survey and Ground Penetrating Radar(GPR). The results of geological survey and boring show the two sets of vertical joint and horizontal joint developed by foliation which is composed of salic and melanic layers. GPR section evidently shows foliation direction and differential weathering due to discontinuity and mineral composition of metamorphic rock. The GPR section for instantaneous phase attribute based on complex trace analysis evidently shows continuity and foliation direction of metamorphic rock. The strong reflection amplitude which is derived from the banded structure of weathered rock can be incorrectly interpreted as a reflection of bedrock. The depth of rock basement should be estimated from the overall exploration result such as boring, seismic method, and electrical resistivity method.

• International Journal of Highway Engineering
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• v.17 no.6
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• pp.1-9
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• 2015

PURPOSES : The objective of this study is to propose a quality control and quality assurance method for use during asphalt pavement construction using non-destructive methods, such as ground penetrating radar (GPR) and an infrared (IR) camera. METHODS : A 1.0 GHz air-coupled GPR system was used to measure the thickness and in situ density of asphalt concrete overlay during the placement and compaction of the asphalt layer in two test construction sections. The in situ density of the asphalt layer was estimated based on the dielectric constant of the asphalt concrete, which was measured as the ratio of the amplitude of the surface reflection of the asphalt mat to that of a metal plate. In addition, an IR camera was used to monitor the surface temperature of the asphalt mat to ensure its uniformity, for both conventional asphalt concrete and fiber-reinforced asphalt (FRA) concrete. RESULTS : From the GPR test, the measured in situ air void of the asphalt concrete overlay gradually decreased from 12.6% at placement to 8.1% after five roller passes for conventional asphalt concrete, and from 10.7% to 5.9% for the FRA concrete. The thickness of the asphalt concrete overlay was reduced from 7.0 cm to 6.0 cm for the conventional material, and from 9.2 cm to 6.4 cm for the FRA concrete. From the IR camera measurements, the temperature differences in the asphalt mat ranged from $10^{\circ}C$ to $30^{\circ}C$ in the two test sections. CONCLUSIONS : During asphalt concrete construction, GPR and IR tests can be applicable for monitoring the changes in in situ density, thickness, and temperature differences of the overlay, which are the most important factors for quality control. For easier and more reliable quality control of asphalt overlay construction, it is better to use the thickness measurement from the GPR.

• ETRI Journal
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• v.38 no.2
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• pp.302-313
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• 2016

Use of a passive bistatic radar (PBR) system in the surveillance or monitoring of an area has its advantages. For example, a PBR system is able to utilize any available signal of opportunity (for example, broadcasting, communication, or radio navigation signals) for the purposes of surveillance. With this in mind, there are potentially many research areas to be explored; in particular, the capability of signals from existing and future communication systems, such as 4G and 5G. Long-Term Evolution (LTE) is the world's most current communication system. Given this fact, this paper presents the latest feasibility studies and experimental results from using LTE signals in PBR applications. Details are provided about aspects such as signal characteristics, experimental configurations, and SNR studies. Six experimental scenarios are carried out to investigate the detection performance of our proposed system on ground-moving targets. The ability to detect is demonstrated through use of the cross-ambiguity function. The detection results suggest that LTE signals are suitable as a source signal for PBR.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1063-1068
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• 2016

Anomalous propagation echo is a kind of abnormal radar signal occurred by irregularly refracted radar beam caused by temperature or humidity. The echo frequently appears in ground-based weather radar due to its observation principle and disturb weather forecasting process. In order to improve accuracy of weather forecasting, it is important to analyze radar data precisely. Therefore, there are several ongoing researches about identifying the anomalous propagation echo with data mining techniques. This paper conducts researches about implementation of classification method which can separate the anomalous propagation echo in the raw radar data using naive Bayes classifier with various kinds of observation results. Considering that collected data has a class imbalanced problem, this paper includes SMOTE method. It is confirmed that the fine classification results are derived by the suggested classifier with balanced dataset using actual appearance cases of the echo.

• Journal of Korea Water Resources Association
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• v.50 no.1
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• pp.1-15
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• 2017

Information on radar rainfall with high spatio-temporal resolution over large areas has been used to mitigate climate-related disasters such as flash floods. On the other hand, a well-known problem associated with the radar rainfall using the Marshall-Palmer relationship is the underestimation. In this study, we develop a new bias correction scheme based on the quantile regression method. This study employed a bivariate copula function method for the joint simulation between radar and ground gauge rainfall data to better characterize the error distribution. The proposed quantile regression based bias corrected rainfall showed a good agreement with that of observed. Moreover, the results of our case studies suggest that the copula function approach was useful to functionalize the error distribution of radar rainfall in an effective way.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.293-302
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• 2014

Radar systems are used in remote sensing mainly as space-borne, airborne and ground-based Synthetic Aperture Radar (SAR), scatterometer and Doppler radar. Those systems are composed of expensive equipments and require expertise and professional skills for operation. Because of the limitation in getting experiences of the radar and SAR systems and its operations in ordinary universities and institutions, it is difficult to learn and exercise essential principles of radar hardware which are essential to understand and develop new application fields. To overcome those difficulties, in this paper, we present the construction and experiment of a low-cost educational radar system based on the blueprints of the MIT Cantenna system. The radar system was operated in three modes. Firstly, the velocity of moving cars was measured in Doppler radar mode. Secondly, the range of two moving targets were measured in radar mode with range resolution. Lastly, 2D images were constructed in GB-SAR mode to enhance the azimuth resolution. Additionally, we simulated the SAR raw data to compare Deramp-FFT and ${\omega}-k$ algorithms and to analyze the effect of antenna positional error for SAR focusing. We expect the system can be further developed into a light-weight SAR system onboard a unmanned aerial vehicle by improving the system with higher sampling frequency, I/Q acquisition, and more stable circuit design.

• Ocean and Polar Research
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• v.26 no.3
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• pp.489-499
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• 2004

The climatological characteristics of the polar ionospheric currents obtained from the simultaneous observations of the ionospheric electric field and conductivity are examined. For this purpose, 43 and 109 days of measurements from the Chatanika and Sondrestrom incoherent scatter radars are utilized respectively. The ionospheric current density is compared with the corresponding ground magnetic disturbance. Several interesting characteristics about the polar ionosphere are apparent from this study: (1) The sun determines largely the conductance over the Sondrestrom radar, while the nighttime conductance distribution over the Chatanika radar is significantly affected by auroral precipitation. (2) The regions of the maximum N-S electric field over the Chatanika radar are located approximately at the dawn and dusk sectors, while they tend to shift towards dayside over the Sondrestrom radar. The N-S component over Son-drestrom is slightly stronger than Chatanika. However, the E-W component over Chatanika is negligible compared to that of Sondrestrom. (3) The E-W ionospheric current flows dominantly in the night hemisphere over Chatanika, while it flows in the sunlit hemisphere over Sondrestrom. The N-S current over Chatanika flows prominently in the dawn and dusk sectors, while a strong southward current flows in the prenoon sector over Sondrestrom. (4) The assumption of infinite sheet current approximation is far from realistic, underestimating the current density by a factor of 2 or more. It is particularly serious for the higher latitude region. (5) The correlation between ${\Delta}H\;and\;J_E$ is higher than the one between ${\Delta}D\;and\;J_N$, indicating that field-aligned current affects ${\Delta}D$significantly.

• Journal of Korea Water Resources Association
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• v.45 no.7
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• pp.657-674
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• 2012

This paper presents the effect of spatially-distributed rainfall on both rainfall-sediment-runoff and erosion or deposition in the experimental Cheoncheon catchment: upstream of Yongdam dam basin. The rainfall fields were generated by three rainfall interpolation techniques (Thiessen polygon: TP, Inverse Distance Weighting: IDW, Kriging) based only on ground gauges and two radar rainfall synthetic techniques (Gauge-Radar ratio: GR, Conditional Merging: CM). Each rainfall field was then assessed in terms of spatial feature and quantity and also used for rainfall-sediment-runoff and erosion-deposition simulation due to the spatial difference of rainfall fields. The results showed that all the interpolation methods based on ground gauges provided very similar hydrologic responses in spite of different spatial pattern of erosion and deposition while raw radar and GR rainfall fields led to underestimated and overestimated simulation results, respectively. The CM technique was acceptable to improve the accuracy of raw radar rainfall for hydrologic simulation even though it is more time consuming to generate spatially-distributed rainfall.