• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.48-54
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• 2008

With the increasing events of natural disasters caused by unpredictable atmospheric movements, the importance of weather forecasting is increasingly emphasized. In this paper, we adopt satellite radar imageries to deal with unusual weather events over Korean region including yellow sand that swept over Korea in spring 2007 and typhoon EWNIAR in 2006. Korea has suffered from these natural events with increasing frequencies over last decades and the satellite radar imaging is considered the most appropriate method to track and analyze the characteristics of the events spanning from mainland China to Japan. The yellow sand mostly comes from Manju area in China and consists of tiny particles so that they move with high speed resulting in difficulty in predicting their moving paths. With the use of various radar images taken at regular time intervals, we could possibly derive the expected movement of the yellow sand particles. In the future, with the help of radar images taken at very short intervals, satellite radar image analysis will become a very useful tool to predict and prepare for the natural disastrous events caused by abrupt change in the atmosphere and deserts around Korea.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.164-170
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• 2012

This paper presents that the comparison results of AT (Active Transponder) positions obtained from different measurements: the result of GPS device and evaluated position from the SAR (Synthetic Aperture Radar) image, and active transponders can be useful as GCPs(Ground Control Points) in SAR images. The X-band AT are installed on the wide-and-flat area to improve SCR(signal-to-clutter ration), and activated to represent impulse response function in order to operate as one point target in SAR images. Cosmo-SkyMed operating at X-band frequency are used to provide SAR images of AT. The comparison of AT position is performed by using the result of GPS device field measurement and AT SAR images. ENVI-SARscape S/W is used to evaluate AT position in the SAR images. From the comparison, it is shown that AT are useful as GCPs for SAR images.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.1
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• pp.17-24
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• 2018

Polar fomat algorithm (PFA) was derived from medical imaging theory, known as back projection, to process synthetic aperture radar(SAR) data. The difference between the operating condition of SAR and back projection assumption makes two distortions. First, the focusing performance of PFA is degraded in proportion to distances from the scene center. Second, the geometric accuracy in SAR images is distorted. Several methods were introduced to mitigate the distortions, but some disadvantages, such as the geometric discontinuity, are arisen when sub-images are combined. This paper proposes the novel method to compensate the geometric distortion with chirp Z-transform (CZT). This method corrects precisely the geometric errors without any problems, because a whole image can be processed all at once.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.121-124
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• 2000

We propose an algorithm for almost unsupervised detection of linear structures, in particular, axes in road network and river, as seen in synthetics aperture radar (SAR) images. The first is local step and used to extract linear features from the speckle radar image, which are treated as road segment candidates. We present two local line detectors as well as a method for fusing Information from these detectors. The second is hybrid step, we Identify the real roads among the segment candidates by defining a Markov random field (MRF) on a set of segments, which introduces contextual knowledge about the shape of road objects.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.193-197
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• 2003

Radar target identification can be achieved by using various radar signatures, such as one-dimensional(1-D) range profile, 2-D radar images, and 1-D or 2-D scattering centers on a target. In this letter, five 1-D scattering center extraction methods are discussed - TLS(Total Least Square)-Prony, Fast Root-MUSIC (Multiple Signal Classification), Matrix-Pencil, GEESE(GEneralized Eigenvalues utilizing Signal-subspace Eigenvalues), TLS-ESPRIT(Total Least Squares - Estimation of Signal Parameters via Rotational Invariance Technique), These methods are compared in the context of estimation accuracy as well as a computational efficiency using a noisy data. Finally these methods are applied to the target classification experiment with the measured data in the POSTECH compact range facility.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.253-259
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• 2016

The typical method for performing an absolute radiometric calibration of a Synthetic Aperture Radar (SAR) System is to analyze its response, without interference, to a target with a known Radar Cross Section (RCS). To minimize interference, an error-free calibration site for a Corner Reflector (CR) is required on a wide and flat plain or on an area without disturbance sources (such as ground objects). However, in reality, due to expense and lack of availability for long periods, it is difficult to identify such a site. An alternative solution is the use of a Triangular Trihedral Corner Reflector (TTCR) site, with a surrounding protection wall consisting of berms and a hollow. It is possible in this scenario, to create the minimum criteria for an effectively error-free site involving a conventional object-tip reflection applied to all beams. Sidelobe interference by the berm is considered to be the major disturbance factor. Total interference, including an object-tip reflection and a sidelobe interference, is analyzed experimentally with SAR images. The results provide a new guideline for the minimum criteria of TTCR site design that require, at least, the removal of all ground objects within the fifth sidelobe.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.262-265
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• 2007

Preliminary results are reported on ship detection using coherence images computed from cross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the different degrees of coherence between the images and water. The polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV. In the next step, we examine the technique when the dual-polarization data are split into two multi-look Images.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.180-184
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• 2008

Preliminary results are reported on ship detection using coherence images computed from crosscorrelating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, crosscorrelation of multi-look images yields the different degrees of coherence between the images and water. The polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV. In the next step, we examine the technique when the dual-polarization data are split into two multi-look images.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.12
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• pp.3-12
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• 2016

This paper describes the development of the ground penetrating radar (GPR) system using UWB impulse radar with 48 Channel array. GPR is an effective alternative technology to resolve th disadvantages of metal detectors. Metal detectors have a very low detection probability of non-metallic landmine and high false alarm rates caused by metallic materials under the ground. In this paper, we use the mono-cycle pulse waveform with about 600 ps pulse width to obtain high resolution landmine microwave images. In order to analyze performances of this system, we utilize indoor test facility that made up of rough sandy loam which representative Korean soil. The mimic landmine models of metal/non-metal and anti-tank/anti-personnel landmines buried in DMZ (demilitarized zone) of Korea are used to analyze the detection depth and the shape of the mines using microwave image.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.8
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• pp.636-645
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• 2017

A scanning radar is exploited widely such as for ground surveillance, disaster rescue, and etc. However, the range resolution is limited by transmitted bandwidth and cross-range resolution is limited by beam width. In this paper, we propose a method for super-resolution radar imaging. If the distribution of reflectivity is sparse, the distribution is called sparse signal. That is, the problem could be formulated as compressive sensing problem. In this paper, 2D super-resolution radar image is generated via reweighted ${\ell}_1-Minimization$. In the simulation results, we compared the images obtained by the proposed method with those of the conventional Orthogonal Matching Pursuit(OMP) and Synthetic Aperture Radar(SAR).