• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.325-331
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• 2017

In this study, digital elevation models(DEM) of tidal flat, according to different times, was produced by means of the Drone and commercial software in order to measure seawater change during high tide at water-channel in the Hampyung Bay. To correct the produced DEMs of the tidal flat where is inaccessible to collect control points, the DEM matching method was applied by using the reference DEM, that is previously obtained, instead of the survey. After the ortho-image was made from the corrected DEM, the land cover classified image was produced. The changes of seawater amount according to the times were analyzed by using the classified images and DEMs. As a result, it was confirmed that the amount of water rapidly increased as the time passed during high tide.

• Korean Journal of Remote Sensing
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• v.20 no.3
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• pp.163-173
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• 2004

The objective of this study is to develop a method to generate micro-relief digital elevation model (DEM) data of the tidal mudflats using multi-temporal Landsat Thematic Mapper (TM) data. Field spectroscopy measurements showed that reflectance of the exposed mudflat, shallow turbid water, and normal coastal water varied by TM band wavelength. Two sets of DEM data of the inter-tidal mudflat area were generated by interpolating several waterlines extracted from multi-temporal TM data acquired at different sea levels. The waterline appearing in the near-infrared band was different from the one in the middle-infrared band. It was found that the waterline in TM band 4 image was the boundary between the shallow turbid water and normal coastal water and used as a second contour line having 50cm water depth in the study area. DEM data generated by using both TM bands 4 and 5 rendered more detailed topographic relief as compared to the one made by using TM band 5 alone.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.310-316
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• 2015

The intertidal area in Lake Sihwa formed after operation of Sihwa-Lake tidal power plant and the change of the area in Lake Sihwa by period were analyzed. For computation of the intertidal area, remote sensing techniques were applied and high resolution Digital Elevation Model (DEM) was generated with root mean square (rms) error 14.4 cm. The intertidal area was $165.1km^2$ in 1910s, $115.2km^2$ in 1991 before completion of Sihwa dyke, $5.6km^2$ in 2010 during the period on operation of sluice gate, and $20.3km^2$ in 2013 after operation of Sihwa tidal power plant. Intertidal in Lake Sihwa was nearly dissipated after completion of Sihwa dyke, but significantly increased with operation of Sihwa tidal power plant from April 2012 as developing a regular tide environment and increasing of sea water flux. The re-formation of tidal flat of Sihwa Lake is an uncommon case. This study that precisely analyzed on the area of artificially formed Sihwa tidal flat would be applicable for management and making conservation plan.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.3
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• pp.190-200
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• 2001

An ecological study was performed to investigate the community structure of the benthic macrofaunal assemblage on the Cheokjeon tidal flat, Incheon, Korea. Benthic samples were collected between Sept. 1990 and July1992 at three stations to compare environmental factors with the structure of benthic community among station sand seasons. Overall, macrofauna comprised a total of 111 species, and the mean density (708.1 md./$m^2$) and biomass (214.9gWWt/$m^2$). The number of species and individuals of polychaetes, molluscs and crustaceans made up more than 80% of the total number. On the other hand, in terms of biomass, bivalves and holothuroideans indicated that they were the dominant faunal groups. Hierarchical classification using the Bray-Curtis coefficient categorized samples into 3 station and 4 faunal groups. In terms of q-mode, there consisted of upper, middle and low tidal flat stations, respectively. And four faunistic groups were established as follows: 1) Heteromastus filifomis-Mactra veneriformis-Solen strictus-Ilyoplax finggi (wide-ranging elevation specialists), 2)Nephtys chemulpoensis-Macrophthalmus gaponicus (high elevation specialists), 3) Glycera subaenea-Decorifer matusimana-Tritodynamia (middle elevation specialists) and 4) Nephtys polybranchia-Borniopsis tsurumaru-Asthenognathus inaequipes-Protankyra bidentata (low elevation Specialists).

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.225-232
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• 2012

In order to evaluate the relationship of between the contents of inorganic elements in shellfish and surface sediments, we measured the concentration of inorganic elements (As, Ca, Cd, Cr, Fe, Hg, Li, Mn, Ni, P, Pb, Zn) in various shellfish and surface sediments of research area. The enrichment factor (EF) and the index of accumulation rate (Igeo) of the metals showed that the research areas can be classified as moderately polluted, or unpolluted. And also we measured the geochemical characteristics of surface sediments(grain size, chemical oxygen demand (COD), ignition loss (IL) and acid volatile sulfide (AVS). The grain sizes for research areas of surface sediment were similar the ratio of silt and clay in comparison with other sites. The COD and IL in surface sediment ranged from 5.41 to 14.06 mg/g. d.w. (mean $8.78{\pm}3.16$ mg/g d.w.) and from 0.92 to 3.17% (mean $2.08{\pm}0.86%$), respectively. Siginificant differences in metal concentrations also were determinated in the shellfish tissue among the different sites. However, except for metals(Mn, Zn), which showed some elevation of concentrations, the variations in the shellfish tissue were not related to variations in the sediment.

• Korean Journal of Remote Sensing
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• v.31 no.5
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• pp.461-471
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• 2015

In this study, we generated orthoimages and Digital Elevation Model (DEM) from Unmanned Aerial Vehicle (UAV) to confirm the accuracy of possibility of geospatial information system generation, then compared the DEM with the topographic height values measured from Real Time Kinematic-GPS (RTK-GPS). The DEMs were generated from aerial triangulation method using fixed-wing UAV and rotary-wing UAV, and DEM based on the waterline method also generated. For the accurate generation of mosaic images and DEM, the distorted images occurred by interior and exterior orientation were corrected using camera calibration. In addition, we set up the 30 Ground Control Points (GPCs) in order to correct of the UAVs position error. Therefore, the mosaic images and DEM were obtained with geometric error less than 30 cm. The height of generated DEMs by UAVs were compared with the levelled elevation by RTK-GPS. The value of R-square is closely 1. From this study, we could confirm that accurate DEM of the tidal flat can be generated using UAVs and these detailed spatial information about tidal flat will be widely used for tidal flat management.

• Korean Journal of Remote Sensing
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• v.16 no.3
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• pp.221-233
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• 2000

An intertidal topography is continuously changed due to morphodynamics processes. Detection and measurement of topographic change for a tidal flat is important to make an integrated coastal area management plan as well as to carry out sedimentologic study. The objective of this study is to generate intertidal DEM using leveling data and waterlines extracted from optical and microwave remotely sensed data in a relatively short period. Waterline is defined as the border line between exposed tidal flat and water body. The contour of the terrain height in tidal flat is equivalent to the waterline. One can utilize satellite images to generate intertidal DEM over large areas. Extraction of the waterline in a SAR image is a difficult task to perform partly because of the presence of speckle and partly because of similarity between the signal returned from the sea surface and that from the exposed tidal flat surface or land. Waterlines in SAR intensity and coherence map can effectively be extracted with MSP-RoA edge detector. From multiple images obtained over a range of tide elevation, it is possible to build up a set of heighted waterline within intertidal zone, and then a gridded DEM can be interpolated. We have tested the proposed method over the Gomso Bay, and succeeded in generating intertidal DEM with relatively high accuracy.

• Journal of Wetlands Research
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• v.13 no.1
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• pp.45-52
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• 2011

Seawater circulations between a bay and the open sea play an important role to make the ecosystem healthy, providing nutrient and oxygen to the benthic environments and cleaning up pollutions. The health of the benthic environment in a bay is closely related to the flushing characteristics of seawater. In this study, to estimate the seawater distribution and circulation characteristics of benthic environment in the Geunso bay, we calculated the hydraulic turn-over time by a hydro-hypsographic analysis. Digital elevation model (DEM) which was generated using waterline method based upon remotely sensed data and water depth of the subtidal zone estimated by echo-sounding survey was applied to the hydro-hypsograhic analysis through a geographic information system (GIS) spatial analysis. The results showed that 95% of the total area of the bay was tidal flat and the hydraulic turn-over time was 1.03 tidal cycle, which indicated that the flushing characteristics of the Geunso bay was very good. Geunso bay was revealed to occupy relatively wide area of benthic environment and to have relatively big tidal range over other domestic and foreign coastal environment, therefore it could have a better seawater circulation characteristics. This result can be effectively applied as fundamental information to establish the system for a quantitative estimate of health of coastal environment in the west coast of Korea and manage the ecosystem in benthic environments.

• Journal of The Geomorphological Association of Korea
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• v.17 no.2
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• pp.29-39
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• 2010

Climate change recently causes rapid rises in sea level in Baramarae intertidal area and the rises present several socio-economic impacts to the affected area. We have assessed the vulnerability of the region by the rise of the sea level. Using quantitative GIS method on multi-temporal satellite images, we have first estimated the elevation (Digital Elevation Model: DEM) of Baramarae intertidal area and hence we were possibly able to identify the flooded areas under the IPCC SRES scenarios. As sea level rises by 20cm, 30cm, 40cm, 50cm and 60 cm, the estimated flooded areas of the tidal flat are 68ha, 85ha, 103ha, 121ha and 139ha, respectively. The most affected area is the tidal flat in Gagyeongju Village (Gonam-li, Gonam-myeon, Taean, Chungnam), because it has not only lower altitude but also, perhaps more significantly smooth slope. The potential affected areas are currently populated by farming of oysters and short-necked clams and therefore the areas expect significant economic loss by rise of sea level.

• 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.