GEO DATA

Data Articles

Waterbody Detection and Reservoir Water Level Prediction Using Bayesian Mixture Models with Sentinel-1 GRD Data: DongHyeon Yoon, Ha-Eun Yu, Euiho Hwang, Ki-mook Kang, Gibeom Nam, Jin-Gyeom Kim; GEO DATA. 2025;7(1):18-26. Published online February 5, 2025; DOI: https://doi.org/10.22761/GD.2024.0052

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Abstract PDF: In this study, we used a Bayesian mixture model (BMM) to monitor water surface areas and estimate water levels in Yeongcheon Dam through Sentinel-1 synthetic aperture radar (SAR) imagery. Reservoirs serve vital functions such as flood control, drought mitigation, and ecosystem support, highlighting the importance of precise monitoring of their water surface and level variations, especially in the context of climate change and increased human impact. The BMM method was employed to accurately delineate water boundaries, benefiting from SAR’s capability to capture data regardless of weather conditions. Regression analysis was conducted between the extracted water surface area and observed water levels to create a predictive model, yielding a highly accurate equation with an R² core of 0.981 on the test set. This result indicates a strong correlation between water surface area and water level, affirming the model’s reliability in estimating water levels based solely on surface area data. One of the key findings of this study is that even with a 10 m spatial resolution, reliable water level inferences can be made using water surface area as a proxy. The mean absolute error values obtained validate the model’s capability to monitor water level fluctuations with a satisfactory degree of accuracy. Despite limitations in detecting narrow tributaries or other small-scale features due to SAR resolution, the model performs well overall in monitoring broad water bodies. These findings underscore the potential of Sentinel-1 SAR data for effective reservoir monitoring, especially where real-time water level data may be lacking. For future research, higher-resolution data or complementary algorithms may further enhance detection accuracy for smaller and more complex water features, contributing to more refined water resource management strategies.

Assessment of the Usability of the Linkage between GLORIA and Sentinel-2 Imagery for the Surveillance of Algal Blooms in Freshwater Ecosystems: Gibeom Nam, Sunghwa Choi, Euiho Hwang, Kimook Kang, JinGyeom Kim, DongHyeon Yoon; GEO DATA. 2024;6(4):451-462. Published online December 31, 2024; DOI: https://doi.org/10.22761/GD.2024.0044

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Abstract PDF: Due to the recent anomalous climatic conditions, the mean summer temperature in Korea for the current year reached 25.6°C, marking the highest temperature recorded since 1973. Concurrently, the incidence of large-scale green algal blooms has escalated beyond the typical frequency in the four principal river systems. The Ministry of Environment has instituted a water quality monitoring network aimed at gathering data pertinent to water quality assessment and regulatory measures; however, the reliance on discrete point data imposes constraints on comprehending the spatial distribution and proliferation of green algae. Techniques for remote monitoring of green algae utilizing satellite imagery may serve as an alternative or complementary resource to conventional point-based water quality assessments. In the present study, we devised and critically assessed an algorithm for the remote estimation of freshwater chlorophyll-a concentrations through the analysis of Sentinel-2 satellite data. Given the challenges associated with field data collection, the GLORIA dataset was employed, and three variations of the CatBoost algorithm were developed based on different input variables, with their effectiveness concerning Sentinel-2 satellite data subjected to evaluation. Among the three algorithms, the variant that was trained utilizing variables such as band ratio and spectral shape was contrasted with 76 field measurements of surface chlorophyll-a, demonstrating a commendable accuracy with an R value of 0.79, root mean square error of 10.1 mg/m³ when applied to the GLORIA dataset. The chlorophyll-a quantification algorithm predicated on Sentinel-2 satellite data, which was developed in this study, holds the potential to be utilized effectively for collaborative management and responsive measures regarding green algae by providing objective insights into the prevalence of green algae across extensive areas, temporal trends, and localized hotspots.

Original Paper

Detection of Floating Debris in the Lake Using Statistical Properties of Synthetic Aperture Radar Pulses: Donghyeon Yoon, Ha-eun Yu, Moung-Jin Lee; GEO DATA. 2023;5(3):185-194. Published online September 27, 2023; DOI: https://doi.org/10.22761/GD.2023.0032

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Abstract PDF: This study developed the European Space Agency (ESA) Setinel-1 Ground Range Detected (GRD) time series analysis model for monitoring floating debris in lake areas through Google Earth Engine Application Programming Interface. The study aims to monitor floating debris caused by heavy rainfall efficiently. Regarding water resources and water quality management, floating debris from multipurpose dams requires continuous monitoring from the initial generation stage. In the study, a Synthetic Aperture Radar (SAR) time series analysis model that is easy to identify water bodies was developed due to low accessibility in large areas. Although SAR satellite images could be used to observe inland water environments, debris detection on water surface surfaces has yet to be studied. For the first time, this study detected floating debris patches in a wide range of lakes from GRD imagery acquired by ESA’s Sentinel-1 satellite. It demonstrated the potential to distinguish them from naturally occurring materials such as invasive floating plants. In this study, the case of Daecheong Dam, in which predicted floating debris was detected after heavy rain using Sentinel-1 GRD data, is presented. It could quickly detect various floating debris flowing into dams used as a source of drinking water and serve as a reference for establishing a collection plan.

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