A Study on the Sedmentary Facies Change in the Tidal Flat Using High Spatial Resolution Remotely Sensed Data

The surface sediment distribution in a tidal flat in 2001 was compared with that of 2008 using high spatial resolution remote sensing images and a GIS-based analysis. Maps of the surface sedimentary facies for each time frame were induced by an IKONOS data acquired in February, 2001 and a KOMPSAT-2 data acquired in April, 2008 using an object-based classification method. The area ratio of each surface sedimentary facies were estimated, and the results were compared each other for deducing the change in the sedimentary facies during the time interval. The result showed that the percentage of grains larger than very fine sand (0.0625 mm) has increased considerably since the early 2000s in the Hwangdo tidal flat. Mud flat facies has decreased 5.81 % in the late 2000s compared with the early 2000s. However, mixed flat and sand flat have increased 4.46% and 2.14%, respectively. A field campaign also supported the result. This study showed that the monitoring of changes in the surface sedimentary facies in the tidal flat is possible through a GIS-based analysis using high spatial resolution remote sensing images. 이 연구에서는 공간해상도 4m 급의 고해상도 위성인 IKONOS 및 Kompsat-2 영상자료와 현장조사 자료를 기반으로 지리정보시스템 분석기법을 적용하여 천수만 황도 갯벌의 표층 퇴적상 분포의 변화 양상을 파악하였다. 2001년 2월에 획득된 IKONOS 영상과 2008년 4월에 획득된 KOMPSAT-2 영상을 이용하여 객체 기반 분류법 (object-based classification)에 의해 갯벌의 표층 퇴적상 분포도를 작성하였다. 두 시기에 얻어진 퇴적상 분포도로부터 각 퇴적상의 면적을 추출하고, 이를 통해 두 시기 동안 연구지역 갯벌의 표층 퇴적상 변화를 분석하였다. 분석 결과, 황도 갯벌에서는 2000년 대 초반에 비해 전반적으로 모래 성분이 증가하여 펄 퇴적상의 상당 부분이 혼합 퇴적상으로 변화한 것으로 나타났다. 펄 퇴적상은 2000년대 초에 비해 후반에 5.81% 증가하였으나, 혼합 퇴적상과 모래 퇴적상은 각각 4.46%와 2.14% 증가하였다. 2004년 4월과 2009년 5월 및 2010년 5월 현장조사 결과에 대한 비교분석을 통해 이를 확인할 수 있었다. 연구 결과, 고해상도 위성영상과 지리정보시스템 분석기법의 활용을 통해 갯벌 표층 퇴적상 분포의 변화 양상을 모니터링하는 것이 가능한 것으로 판단된다.22Nkc

고해상도 위성영상을 이용한 경기만 조석사주의 장기 변화 관측

서해 경기만은 조석작용이 강한 대조차 연안환경으로 한강, 예성강, 임진강으로부터 유입된 부유퇴적물이 석모수로와 염하수로를 통하여 유입된다. 이러한 경기만 연안 지역에는 활발한 조석 및 파랑활동으로 인하여 거대한 조석사주가 많이 발달하였다. 하지만 경기만 일대에서의 간척 사업 등의 개발로 인하여 연안 해수 흐름의 방향 및 속도 변화가 발생되었다. 이로 인해 조석 사주 면적 및 위치 변화 등과 같은 연안 환경 변화가 나타난다. 기존에는 이러한 변화를 탐지하기 위해서는 현장 조사를 통한 연구가 진행되었지만, 공간적으로 넓은 지역의 변화 관측에는 한계점이 있다. 이를 보완하기 위하여 인공위성을 활용한 연구가 많이 진행되고 있다. 따라서 이번 연구에서는 Landsat 위성영상을 활용하여 조석 사주 변화에 대한 연구를 하고자 한다. 연구에 사용한 위성영상은 Landsat 4 MSS, Landsat 5 TM, Landsat 7 ETM+ 영상으로 1980년대부터 2000년대 초반의 약 20년 동안의 동일한 계절의 영상을 분석하였다. 또한 최대한 유사한 조석상태 및 조위의 영상을 비교하였다. 그 결과 경기만 지역에서 조석 사주의 변화가 관측되었고 Landsat 영상의 30m 공간 해상도 덕분에 면적이 작은 사주 변화 관측이 가능하였다. 추후 다양한 영상 자료 및 퇴적 환경 자료와 모델링 분석을 통하여 경기만 일대의 조석사주가 어떠한 방향으로 변화되어 왔으며, 향후 어떠한 변화가 일어날 수 있는지에 대한 연구가 필요하다.2

Application of unmanned aerial vehicles (UAVs) for generating high-resolution intertidal DEM

Recently, the UAVs have been widely used in aerial survey. UAVs are classified into rotary wing and fixed-wing type. In order to demonstrate the suitability of UAVs to the tidal flat study, we tested fixed-wing UAV mounted with Canon S95 and rotary-wing UAV mounted with Canon 6D. For the accurate geometric correction, it is necessary that pre-processing and post-processing of the obtained image. The interior and exterior orientation parameters were obtained based on the lens distortion model. For the accurate mosaic image generation, the topographic height of the tidal flat was measured using RTK-GPS and flight plans were prepared to obtain 70% image overlap to the azimuth direction and 40% to the range direction. For the mosaic image based on the rotary-wing UAV, waterlines were extracted from each image, and DEM was generated using a waterline method. For the mosaic image based on the fixed-wing UAV, DEM was obtained by aerial triangulation when tidal flat was fully exposed. The accuracy of DEM from fixed-wing UAV was higher than that from rotary-wing UAV. The Fixed-wing UAVs have a limitation to mount various cameras such as DSLR. However, the rotary-wing UAVs can mount not only high-resolution optical cameras such as DSLR but also multispectral, hyperspectral and thermal sensors. In conclusion, the fixed-wing UAVs are advantageous for the analysis on topographic changes, and the rotary-wing UAVs are advantageous d rotary-wing UAV mounted with Canon 6D. For the accurate geometric correction, it is necessary that pre-processing and post-processing of the obtained image. The interior and exterior orientation parameters were obtained based on the lens distortion model. For the accurate mosaic image generation, the topographic height of the tidal flat was measured using RTK-GPS and flight plans were prepared to obtain 70% image overlap to the azimuth direction and 40% to the range direction. For the mosaic image based on the rotary-wing UAV, waterlines were extracted from each image, and DEM was generated using a waterline method. For the mosaic image based on the fixed-wing UAV, DEM was obtained by aerial triangulation when tidal flat was fully exposed. The accuracy of DEM from fixed-wing UAV was higher than that from rotary-wing UAV. The Fixed-wing UAVs have a limitation to mount various cameras such as DSLR. However, the rotary-wing UAVs can mount not only high-resolution optical cameras such as DSLR but also multispectral, hyperspectral and thermal sensors. In conclusion, the fixed-wing UAVs are advantageous for the analysis on topographic changes, and the rotary-wing UAVs are advantageous1

Application of Unmanned Aerial Vehicle to the mapping of a tidal flat Digital Elevation Model

In order to demonstrate the suitability of UAVs to the tidal flat study, we tested fixed-wing UAV mounted with Canon S95 and rotary-wing UAV mounted with Canon 6D. For the accurate geometric correction, it is necessary that pre-processing and post-processing of the obtained image. The interior and exterior orientation parameters were obtained based on the lens distortion model. For the accurate mosaic image generation, the topographic height of the tidal flat was measured using RTK-GPS and flight plans were prepared to obtain 70% image overlap to the azimuth direction and 40% to the range direction. For the mosaic image based on the rotary-wing UAV, waterlines were extracted from each image, and DEM was generated using a waterline method. For the mosaic image based on the fixed-wing UAV, DEM was obtained by aerial triangulation when tidal flat was fully exposed. The accuracy of DEM from fixed-wing UAV was higher than that from rotary-wing UAV. The Fixed-wing UAVs have a limitation to mount various cameras such as DSLR. However, the rotary-wing UAVs can mount not only high-resolution optical cameras such as DSLR but also multispectral, hyperspectral and thermal sensors. In conclusion, the fixed-wing UAVs are advantageous for the analysis on topographic changes, and the rotary-wing UAVs are advantageous for the analysis on surface characteristics such as vegetation and sedimentary facies along with various multispectrand post-processing of the obtained image. The interior and exterior orientation parameters were obtained based on the lens distortion model. For the accurate mosaic image generation, the topographic height of the tidal flat was measured using RTK-GPS and flight plans were prepared to obtain 70% image overlap to the azimuth direction and 40% to the range direction. For the mosaic image based on the rotary-wing UAV, waterlines were extracted from each image, and DEM was generated using a waterline method. For the mosaic image based on the fixed-wing UAV, DEM was obtained by aerial triangulation when tidal flat was fully exposed. The accuracy of DEM from fixed-wing UAV was higher than that from rotary-wing UAV. The Fixed-wing UAVs have a limitation to mount various cameras such as DSLR. However, the rotary-wing UAVs can mount not only high-resolution optical cameras such as DSLR but also multispectral, hyperspectral and thermal sensors. In conclusion, the fixed-wing UAVs are advantageous for the analysis on topographic changes, and the rotary-wing UAVs are advantageous for the analysis on surface characteristics such as vegetation and sedimentary facies along with various multispectra1

Dynamic variations in coastal water turbidity identified from the world’s first geostationary ocean colour imager

Temporal variations of suspended sediment concentration (SSC) in coastal water are the key to understanding the pattern of sediment movement within coastal area, in particular, such as in the west coast of the Korean Peninsula which is influenced by semi-diurnal tides. Remote sensing techniques can effectively monitor the distribution and dynamic changes in seawater properties across wide areas. An advantage of Geostationary Ocean Color Imager (GOCI), the world’s first geostationary ocean color observation satellite, over other ocean color satellite images is that it can obtain data every hour during the day and makes it possible to monitor the ocean in real time. In this study, hourly variations in turbidity on the coastal waters were estimated quantitatively using GOCI. Water samples were obtained on the coastal water in the west coast of Korea and were filtered using 25-mm glass fiber filters (GF/F) for the estimation of SSC. The radiometric characteristics of the surface water, such as the total water-leaving radiance (LwT, W/m2/nm/sr), the sky radiance (Lsky, W/m2/nm/sr) and the downwelling irradiance, were also measured at each sampling location. In situ optical properties of the surface water were converted into remote sensing reflectance (Rrs) and then were used to develop an algorithm to generate SSC images in the study area. GOCI images acquired on the same day as the samples acinfluenced by semi-diurnal tides. Remote sensing techniques can effectively monitor the distribution and dynamic changes in seawater properties across wide areas. An advantage of Geostationary Ocean Color Imager (GOCI), the world’s first geostationary ocean color observation satellite, over other ocean color satellite images is that it can obtain data every hour during the day and makes it possible to monitor the ocean in real time. In this study, hourly variations in turbidity on the coastal waters were estimated quantitatively using GOCI.1

Coral reef habitat mapping using high spatial resolution satellite images

Coral reefs and associated tropical nearshore ecosystems have suffered massive, long-term changes in abundance, diversity, and habitat structure due to overfishing and pollution. Especially, the global warming has lead to the global decrease in the coral reefs recently, thus the coral reef habitat can be a good indicator of environmental change in a tropical coastal area. In this study, we carried out the analysis of coral reef habitat change using KOMPSAT-2 images in Weno island, Chuuk lagoon of Federated States of Micronesia. A field campaign was performed for collecting real reef habitat data in 2008 and 2011. The satellite image was acquired on September 2008 and 2010. For classification of KOMPSAT-2 images, we employed an object-based classification method which has been considered to be effective for high spatial resolution satellite images. The produced habitat map was validated by a comparison with the in-situ observations. The overall accuracy calculated from the classification results of the KOMPSAT-2 image in 2008 was 84.62 %. And The KOMPSAT-2 image acquired in 2010 was 87.25%. In addition, area of coral reef habitat mapping has changed during 2 years. Through the research, high resolution satellite images can be possible to monitor of coral reef habitat changerease in the coral reefs recently, thus the coral reef habitat can be a good indicator of environmental change in a tropical coastal area. In this study, we carried out the analysis of coral reef habitat change using KOMPSAT-2 images in Weno island, Chuuk lagoon of Federated States of Micronesia. A field campaign was performed for collecting real reef habitat data in 2008 and 2011. The satellite image was acquired on September 2008 and 2010. For classification of KOMPSAT-2 images, we employed an object-based classification method which has been considered to be effective for high spatial resolution satellite images. The produced habitat map was validated by a1

A study on the satellite-based sea surface salinity mapping in Korean coastal waters

Sea surface salinity (SSS) is an important factor in the ocean science, such as estimating oceanic carbon flux, tracing red tide, and calculating other physical processes at the surface. Sea surface salinity can be derived from satellite remote sensing, although little has been successful particularly in the coastal waters. It is well-known that absorption property of colored dissolved organic matter (CDOM) absorption has a strong correlation with SSS in the area that influenced by freshwater inflow. Here, we tested the applicability of CDOM distribution observed from the Geostationary Ocean Colour Imager (GOCI) to mapping SSS in the Korean coastal waters. Empirical relationships between CDOM absorption and SSS are derived from in-situ measurement collected at the Gyeonggi-bay located in the middle of the west coast of Korean peninsula. SSS images derived from GOCI were validated by comparison with the in-situ measurement and were also compared with SSS images provided from HYCOM-modelled, which shows that it is possible to estimate SSS from CDOM absorption at the estuarine environment. Further studies would be needed to improve the algorithm and apply it to other coastal environments around the Korean peninsula. Satellite based SSS from this study can be used for studies on the long-term variations in SSS in this area and its relations with the climate changes.mote sensing, although little has been successful particularly in the coastal waters. It is well-known that absorption property of colored dissolved organic matter (CDOM) absorption has a strong correlation with SSS in the area that influenced by freshwater inflow. Here, we tested the applicability of CDOM distribution observed from the Geostationary Ocean Colour Imager (GOCI) to mapping SSS in the Korean coastal waters. Empirical relationships between CDOM absorption and SSS are derived from in-situ measurement collected at the Gyeonggi-bay located in the middle of the west coast of Korean peninsula. SSS images derived from GOCI were validated by comparison with the in-situ measurement and were also compared with SSS images provided from HYCOM-modelled, which shows that it is possible to estimate SSS from CDOM absorption at the estuarine environment. Further studies would be needed to improve the algorithm and apply it to other coastal environments around the Korean peninsula. Satellite based SSS from this study can be used for studies on the long-term variations in SSS in this area and its relations with the climate changes.1

Long-term Seagrass Mapping using Multi-satellite Sensors at Deukryang bay, Korea

해초지는 연안 생태계 내의 물질순환을 주도하고, 어류의 산란 및 성육장을 제공하는 등생태적으로 매우 중요한 서식지 임에도 불구하고, 국내 연안에 분포하는 해초지 규모에 대한 정보는 부족한 실정이다. 따라서 이 연구에서는 다양한 공간해상도의 Landsat TM/ETM+, Aster, Spot-4, Kompsat-2 인공위성영상 분석을 통해 1990년부터 2012년까지 득량만 잘피의 분포 변화를 분석하였다. 수중음향탐사를 통한 현장조사 자료를 기반으로 Mahalanobis Distance Classification 기법을 통해 해초지를 분류하였고, Error Matrix를 통해 분류 정확도를 평가하였다. 현장조사 시기에 획득된 위성영상인 Kompsat-2 위성영상의 해초지 분류 정확도는 약 73%로 계산되었다. 득량만 해초지는 2011년 2.0 km2로 최소 분포를 보였고, 1999년 6.3 km2로 최대 분포를 보였으며, 평균 분포 면적은 약 4.6 km2 이었다. 득량만 해초지는 수온, 강수량, 일조량 등 다양한 물리환경 변화에도 불구하고 조사기간 동안 대체로 안정적인 분포면적을 유지하는 것으로 나타났다. 다만 2012년 연구해역을 통과한 연속적인 태풍에 의해 분포면적이 급격히 감소된 것으로 조사되었다. 인공위성영상 분석을 통한 해초지 분포면적 추정 연구를 통해 해초지의 장기변동 추이 자료도출이 가능하였고, 이 자료는 해초지 장기 생태특성을 이해하고, 이들의 효율적 관리에 중요한 정보를 제공할 것으로 기대된다.t TM/ETM+, Aster, Spot-4, Kompsat-2 인공위성영상 분석을 통해 1990년부터 2012년까지 득량만 잘피의 분포 변화를 분석하였다. 수중음향탐사를 통한 현장조사 자료를 기반으로 Mahalanobis Distance Classification 기법을 통해 해초지를 분류하였고, Error Matrix를 통해 분류 정확도를 평가하였다. 현장조사 시기에 획득된 위성영상인 Kompsat-2 위성영상의 해초지 분류 정확도는 약 73%로 계산되었다. 득량만 해초지는 2011년 2.0 km2로 최소 분포를 보였고, 1999년 6.3 km2로 최대 분포를 보였으며, 평균 분포 면적은 약 4.6 km2 이었다. 득량만 해초지는 수온, 강수량, 일조량 등 다양한 물리환경 변화에도 불구하고 조사기간 동안 대체로 안정적인 분포면적을 유지하는 것으로 나타났다. 다만 2012년 연구해역을 통과한 연속적인 태풍에 의해 분포면적이 급격히 감소된 것으로 조사되었다. 인공위성영상 분석을 통한 해초지 분포면적 추정 연구를 통해 해초지의 장기변동 추이 자료도출이 가능하였고, 이 자료는 해초지 장기 생태특성을 이해하고, 이들의 효율적 관리에 중요한 정보를 제공할 것으로 기대된다.2

Spatial and temporal variability of the suspended sediment distribution observed by remote sensing

Variation in the transport of fine sediment is at the heart of many ecosystem functions, such as biochemical cycling, movement of nutrients, biodiversity maintenance, biological production, and mitigation of floods (Eleveld et al., 2014 Miere et al., 2005). Monitoring of suspended particulate matter (SPM) concentrations is useful in ecological management and to draft legislation, because dynamic variations in the SPM on the sea surface provide clues to underlying sedimentary processes (Chen et al., 2007 Torres & Morelock, 2002). Analysis of SPM is a key to understanding the turbulent quantities of sediment flow in the Heuksan mud belt (HMB) located along the southwestern coast of the Korean Peninsula. The purpose of this study was to investigate intra-annual variability in remotely sensed SPM derived from the Geostationary Ocean Color Imager (GOCI) and sea surface temperature (SST) based on the Advanced Very High Resolution Radiometer (AVHRR), respectively, around the HMB over a period of 1 year (2013). Monthly composite SPM images showed pronounced seasonal changes in turbid water. The extent of turbid water increased during the winter season along Gomso Bay to Jangsado, whereas it decreased during the summer months from Yeonggwang to Sinan. A comparison of monthly composite SST images and wind data showed that the northwesterly winds of monsoons and net heat loss from the sea surface to the atmosphere resulted inere et al., 2005). Monitoring of suspended particulate matter (SPM) concentrations is useful in ecological management and to draft legislation, because dynamic variations in the SPM on the sea surface provide clues to underlying sedimentary processes (Chen et al., 2007 Torres & Morelock, 2002). Analysis of SPM is a key to understanding the turbulent quantities of sediment flow in the Heuksan mud belt (HMB) located along the southwestern coast of the Korean Peninsula. The purpose of this study was to investigate intra-annual variability in remotely sensed SPM derived from the Geostationary Ocean Color Imager (GOCI) and sea surface temperature (SST) based on the Advanced Very High Resolution Radiometer (AVHRR), respectively, around the HMB over a period of 1 year (2013). Monthly composite SPM images showed pronounced seasonal changes in turbid water. The extent of turbid water increased during the winter season along Gomso Bay to Jangsado, whereas it decreased during the summer months from Yeonggwang to Sinan. A comparison of monthly composite SST images and wind data showed that the northwesterly winds of monsoons and net heat loss from the sea surface to the atmosphere resulted in1

Application of the GOCI to estimates of ocean surface currents and fronts

The Geostationary Ocean Color Imager (GOCI) can be utilized to observe subtle changes in oceanic environments because it receives ocean color data around the Northeast Asia every hour, eight times a day. This study focused on 1) estimating ocean surface currents and 2) extracting ocean fronts, using GOCI. To estimate currents, the maximum cross correlation (MCC) based algorithm was proposed. The total suspended sediment (TSS) was used to approximately estimate semi-diurnal tidal currents in highly turbid coastal waters, and the chlorophyll concentration (chl) was employed for relatively clear waters. In the results, it was validated that the currents estimated by the proposed algorithm trace dynamic movements on the west coast of Korea and represent well the movements along boundaries where warm and cold seawaters mix in the East/Japan Sea. To extract fronts, we developed a histogram-based methodology. In order to validate oceanic changes in the coastal region which has extremely high turbidities, the fronts derived from TSS were used. On the other hand, the fronts derived from chl were exploited to investigate oceanic changes in the offshore which has relatively low turbidities. In the results deduced from the TSS front, statistics of semi-diurnal changes for the tide in the coastal region were approximately measured, and we could find out that the extracted fronts are quite relevant to the topographical characterisocean surface currents and 2) extracting ocean fronts, using GOCI. To estimate currents, the maximum cross correlation (MCC) based algorithm was proposed. The total suspended sediment (TSS) was used to approximately estimate semi-diurnal tidal currents in highly turbid coastal waters, and the chlorophyll concentration (chl) was employed for relatively clear waters. In the results, it was validated that the currents estimated by the proposed algorithm trace dynamic movements on the west coast of Korea and represent well the movements along boundaries where warm and cold seawaters mix in the East/Japan Sea. To extract fronts, we developed a histogram-based methodology. In order to validate oceanic changes in the coastal region which has extremely high turbidities, the fronts derived from TSS were used. On the other hand, the fronts derived from chl were exploited to investigate oceanic changes in the offshore which has relatively low turbidities. In the results deduced from the TSS front, statistics of semi-diurnal changes for the tide in the coastal region were approximately measured, and we could find out that the extracted fronts are quite relevant to the topographical characteris1