• Journal of Wetlands Research
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• v.8 no.3
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• pp.29-38
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• 2006

Digital Elevation Model (DEM) of intertidal flat can be widely used not only for scientific fields, coastal management, fisheries, ocean safety, military, but also for understanding natural and artificial topographic changes of the tidal flat. In this study, we generated DEM of the Ganghwado southern intertidal flat, the largest tidal flat in the west coast of the Korean Peninsula, using waterline method and interferometric synthetic aperture radar (InSAR). Constructed DEM which applied waterline method to the Landsat-5 TM and Landsat-7 ETM+ images closely expresses overall topographic relief of tidal flat. We found that the accuracy was determined by the number of waterlines which reflect various tidal conditions. The application of InSAR to the ERS-1/2 and ENVISAT images showed that only ERS-1/2 tandem pairs successfully generated DEM in the part of northern Yeongjongdo, but construction of DEM in the other areas was difficult due to the low coherence caused by a lot of surface remnant waters. In the near future, Kompsat-2 will provide satellite images having multi-spectral and high spatial resolution within a relatively short period at different sea levels. Application of waterline method to these images will help us construct a high precision tidal flat DEM. Also, we should develop DEM generation method using single-pass microwave satellite images.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.425-428
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• 1999

The radar interferogram represents phase differences between the two synthetic aperture radar observations acquired in slightly different angle. The success of the radar interferometric application largely depends on the quality of the interferogram generated from two or more synthetic aperture radar data sets. We propose here to apply the wavenumber correlation analysis to the in-phase and quadrature phase of the radar interferogram. The wavenumber correlation analysis is to resolve the highly correlated components from the low correlation components by estimating correlation coefficients for each wavenumber component. Through this approach, one can easily distinguish the signal components from the noise components in the wavenumber domain. Therefore, the wavenumber correlation analysis of the radar interferogram can be utilized to design post filter and to estimate the quality of interferogram. We have tested the wavenumber correlation analysis using a Radarsat SAR data pair to demonstrated the effectiveness of

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1235-1249
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• 2019

Kilauea Volcano is one of the most active volcano in the world. In this study, we used the ALOS-2 PALSAR-2 satellite imagery to measure the surface deformation occurring near the summit of the Kilauea volcano from 2015 to 2017. In order to measure two-dimensional surface deformation, interferometric synthetic aperture radar (InSAR) and multiple aperture SAR interferometry (MAI) methods were performed using two interferometric pairs. To improve the precision of 2D measurement, we compared root-mean-squared deviation (RMSD) of the difference of measurement value as we change the effective antenna length and normalized squint value, which are factors that can affect the measurement performance of the MAI method. Through the compare, the values of the factors, which can measure deformation most precisely, were selected. After select optimal values of the factors, the RMSD values of the difference of the MAI measurement were decreased from 4.07 cm to 2.05 cm. In each interferograms, the maximum deformation in line-of-sight direction is -28.6 cm and -27.3 cm, respectively, and the maximum deformation in the along-track direction is 20.2 cm and 20.8 cm, in the opposite direction is -24.9 cm and -24.3 cm, respectively. After stacking the two interferograms, two-dimensional surface deformation mapping was performed, and a maximum surface deformation of approximately 30.4 cm was measured in the northwest direction. In addition, large deformation of more than 20 cm were measured in all directions. The measurement results show that the risk of eruption activity is increasing in Kilauea Volcano. The measurements of the surface deformation of Kilauea volcano from 2015 to 2017 are expected to be helpful for the study of the eruption activity of Kilauea volcano in the future.

• Proceedings of the KSRS Conference
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• v.1
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• pp.368-371
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• 2006

A coastline is the boundary between land and ocean masses. Knowledge of coastline is essential for autonomous navigation, geographical exploration, coastal erosion monitoring and modelling, water line change, etc. Many methods have been researched to extract coastlines from the synthetic aperture radar (SAR) and optic images. Most methods were based on the intensity contrast between land and sea regions. However, in these methods, a coastline detection task was very difficult because of insufficient intensity contrast and the ambiguity in distinguishing coastline from other object line. In this paper, we propose an efficient method for the delineation of coastline using interferometric coherence values estimated from ERS tandem pair. The proposed method uses the facts that a tandem pair of ERS is acquired from a time interval of an accurate day and that the coherent and incoherent values in coherence map are land and water, respectively. The coherence map was generated from ERS tandem pair, filtered by MAP filter, and divided into land and water by the determination of threshold value that is based on the bimodality of the histogram. Finally, a coastline was detected by delineating the boundary pixels. There was a good visual match between the detected coastline and the manually contoured line. The interferometric coherence map will be helpful to identify land and water regions easily, and can be used to many applications that are related with a coastline.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.81-87
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• 2015

We present an implementation result of a computer GUI-based simulator using MATLAB to verify the performance of interferometric radar altimeter(IRA) which is possible to measure the slant range altitude and the cross-track angle to the nearest point for terrain aided navigation(TAN). After a brief description of the principle of TAN and IRA, we present that the grids are divided for the modeling of the reflected signal in digital elevation map(DEM) and so the radar cross section(RCS) of each grid is calculated and the signal-noise ratio(SNR) of the reflected signal in the radar beam width. And the signal processing procedures of the IRA and the structure of the IRA simulator are shown.

• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.13-22
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• 2021

The ML 5.8 earthquake shocked Gyeongju, Korea, at 11:32:55 UTC on September 12, 2016. One year later, on the afternoon of November 15, 2017, the ML 5.4 earthquake occurred in Pohang, South Korea. The earthquakes injured many residents, damaged buildings, and affected the economy of Gyeongju and Pohang. The damage proxy maps (DPMs) were generated from Sentinel-1 synthetic aperture radar (SAR) imagery by comparing pre- and co-events interferometric coherences to identify anomalous changes that indicate damaged by the earthquakes. DPMs manage to detect coherence loss in residential and commercial areas in both Gyeongju and Pohang earthquakes. We found that our results show a good correlation with the Korea Meteorological Administration (KMA) report with Modified Mercalli Intensity (MMI) scale values of more than VII (seven). The color scale of Sentinel-1 DPMs indicates an increasingly significant change in the area covered by the pixel, delineating collapsed walls and roofs from the official report. The resulting maps can be used to assess the distribution of seismic damage after the Gyeongju and Pohang earthquakes and can also be used as inventory data of damaged buildings to map seismic vulnerability using machine learning in Gyeongju or Pohang.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1657-1667
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• 2021

Anthropogenic activities and natural processes have been causes of land subsidence which is sudden sinking or gradual settlement of the earth's solid surface. Mexico City, the capital of Mexico, is one of the most severe land subsidence areas which are resulted from excessive groundwater extraction. Because groundwater is the primary water resource occupies almost 70% of total water usage in the city. Traditional terrestrial observations like the Global Navigation Satellite System (GNSS) or leveling survey have been preferred to measure land subsidence accurately. Although the GNSS observations have highly accurate information of the surfaces' displacement with a very high temporal resolution, it has often been limited due to its sparse spatial resolution and highly time-consuming and high cost. However, space-based synthetic aperture radar (SAR) interferometry has been widely used as a powerful tool to monitor surfaces' displacement with high spatial resolution and high accuracy from mm to cm-scale, regardless of day-or-night and weather conditions. In this paper, advanced interferometric approaches have been applied to get a time-series of land subsidence of Mexico City using four-year-long twenty ALOS PALSAR L-band observations acquired from Feb-11, 2007 to Feb-22, 2011. We utilized persistent scatterer interferometry (PSI) and small baseline subset (SBAS) techniques to suppress atmospheric artifacts and topography errors. The results show that the maximum subsidence rates of the PSI and SBAS method were -29.5 cm/year and -27.0 cm/year, respectively. In addition, we discuss the different subsidence rates where the study area is discriminated into three districts according to distinctive geotechnical characteristics. The significant subsidence rate occurred in the lacustrine sediments with higher compressibility than harder bedrock.

• Korean Journal of Remote Sensing
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• v.28 no.1
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• pp.121-128
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• 2012

High resolution intertidal DEM is a basic material for science research like sedimentation/erosion by ocean current, and is invaluable in a monitoring of environmental changes and practical management of coastal wetland. Since the intertidal zone changes rapidly by the inflow of fluvial debris and tide condition, remote sensing is an effective tool for observing large areas in short time. Although radar interferometry is one of the well-known techniques for generating high resolution DEM, conventional repeat-pass interferometry has difficulty on acquiring enough coherence over tidal flat due to the limited exposure time and the rapid changes in surface condition. In order to overcome these constraints, we tested the feasibility of radar interferometry using Cosmo-SkyMed tandem-like one-day data and ERS-ENVISAT cross tandem data with very short revisit period compared to the conventional repeat pass data. Small temporal baseline combined with long perpendicular baseline allowed high coherence over most of the exposed tidal flat surface in both observations. However the interferometric phases acquired from Cosmo-SkyMed data suffer from atmospheric delay and changes in soil moisture contents. The ERS-ENVISAT pair, on the other hand, provides nice phase which agree well with the real topography, because the atmospheric effect in 30-minute gap is almost same to both images so that they are cancelled out in the interferometric process. Thus, the cross interferometry with very small temporal baseline and large perpendicular baseline is one of the most reliable solutions for the intertidal DEM construction which requires very accurate mapping of the elevation.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.495-505
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• 2023

The Musan mine, situated in Musan County, Hamgyong Province, North Korea, stands as a prominent open-pit iron mine on the Korean Peninsula. This study focuses on estimating the mining and dumping activities within the Musan mine area by analyzing digital elevation model (DEM) changes. To calculate the long-term volume changes in the Musan mine, we digitized and converted the 1:200,000-scale third topographic map of the Joseon published in 1918 and compared with interferometric synthetic aperture radar (InSAR) DEMs, including Shuttle Radar Topography Mission DEM (2000) and Copernicus DEM (2011-2015). The findings reveal that over a century, Musan mine yielded around 1.37 billion tons of iron ore, while approximately 1.06 billion tons of waste rock were dumped. This study is particularly significant as it utilizes a historical topographic map predating the full-scale development of Musan mine to estimate a century's mining production and waste rock deposition. It is expected that this research provides valuable insights for future investigation of surface change of North Korea where the acquisition of in situ data remains challenging.