GEO DATA

Original Papers

Detailed Bathymetry and Seafloor Backscatter Image Dataset for Monitoring Ecosystem Environment: Southern Ulleungdo: Soon Young Choi, Chang Hwan Kim, Won Hyuck Kim, Chan Hong Park; GEO DATA. 2023;5(4):364-370. Published online December 27, 2023; DOI: https://doi.org/10.22761/GD.2023.0037; Correction in: GEO DATA 2024;6(1):43

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Abstract PDF: We obtained a detailed bathymetry dataset using multi-beam echo sounder around Neunggeol located at Southern part in Ulleungdo. The survey period was from September 1, 2019 and the bathymetry survey was carried out by RV Jangmok No2 of Korea Institute of Ocean Science and Technology. The instrument equipment used for the survey were Kongsbergs’s EM2040 (multi-beam echo sounder). The detailed bathymetry of the study area shows gradually depth change from about 4 to 190 m. The study area has relatively gentle slopes from the coast to 25 m and below about 125 m in depth, but a steep slope from about 25 to 125 m. The rocky bottom zones identified from detailed bathymetry and backscattered seafloor images are distributed in the northeastern sea of the coastal area, the central sea, and around Neunggeol. In particular, Neunggeol and the near large outcropping rock are tumulus-like submarine landforms, forming big vertical walls. The submarine cable buried between Ulleungdo and the Korean mainland appears in the northern seafloor of the survey area. Stopper stones and gravels sediment are distributed around it. The rocky bottom zone has a strong and irregular reflection intensity in the seafloor backscattered image and the sandy sediment zone has a relatively weak reflection intensity and a uniform pattern, so the two zones are well divided. We classified the sediment zones into fine-grained sediments, sandy sediments, and gravel-like sediments by using the different reflection intensities due to differences in sediment particle size in the seafloor image. Detailed bathymetry and seafloor backscattered image dataset around Neunggeol can be used as a basic data for habitat environment mapping.

Riverine Bathymetry Survey Using Unmanned Aerial Vehicle-Based Multispectral Image: Yeonghwa Gwon, Dongsu Kim, Siyoon Kwon; GEO DATA. 2023;5(3):195-206. Published online September 27, 2023; DOI: https://doi.org/10.22761/GD.2023.0033

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Abstract PDF: River basin surveys are conducted with the aim of providing essential foundational information for the formulation of water management policies, as mandated by relevant laws and regulations. These surveys cover key investigation areas necessary for river basin management, including basic conditions, water conveyance, dimensions, environmental ecology, and more. Among the survey methods, the utilization of remote sensing data, such as drone monitoring imagery and satellite imagery, is employed for various purposes such as the safety management of hydraulic structures like dams and embankments, water quality monitoring, river terrain surveys, and assessments of changes in riverbeds. Recently, research in river basin studies has been conducted using hyperspectral imagery, which includes hundreds of spectral bands, in addition to standard RGB imagery. Hyperspectral imagery offers the advantage of high spectral resolution, making it suitable for multi-parameter assessments. However, it comes with the drawback of large initial data volumes and complex preprocessing requirements due to the abundance of spectral information. On the other hand, multispectral imagery, which collects spectral information from fewer than ten bands, is widely used, especially in agriculture and forestry. It allows for immediate monitoring of parameters like the normalized difference vegetation index (NDVI) using just two bands and facilitates the analysis of crop growth status and more. Research on bathymetric estimation using hyperspectral imagery has traditionally relied on the Optimal Band Ratio Analysis (OBRA), which utilizes band ratios highly correlated with depth to construct bathymetric maps. In this study, we applied the existing hyperspectral bathymetric estimation technique to multispectral imagery to assess the feasibility of bathymetric estimation using reduced spectral bands. We captured multispectral imagery and constructed bathymetric maps to evaluate the applicability of multispectral imagery in river basin applications. Furthermore, to overcome the limitations of traditional OBRA, we employed Gaussian mixture models for image clustering to improve the accuracy of bathymetric estimation.

Article

Detailed bathymetry and seafloor image datasets, using multi-beam echo sounder and side scan sonar, around Seonam, Ilsan beach, Ulsan: Soon Young Choi, Chang Hwan Kim, Won Hyuck Kim, Hyun-Ok Choi, Chan Hong Park, Feel Hoon Go; GEO DATA. 2022;4(4):1-12. Published online December 31, 2022; DOI: https://doi.org/10.22761/DJ2022.4.4.001

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Abstract PDF: We obtained detailed bathymetry and seafloor image datasets using multi-beam echo sounder and side scan sonar around Seonam at Ilsan beach in Ulsan. The survey was conducted from May 9 to May 12, 2018, using a small vessel. The equipment used for the survey was R2Sonic's Sonic 2020 (Multi-beam Echo Sounder) and EdgeTech’s 4125 (Side Scan Sonar). The detailed bathymetry of the study area shows slightly different topographical features for each part around Seonam. The eastern and southern parts have steep slopes and the depth of the water in the areas deepens away from the surroundings of the submerged bedrock area adjacent to Seonam. The water depth in the western and northern part is shallower with a relatively gentle slope, compared to the eastern and southern parts. The rocky bottom zones are mainly distributed in the eastern part area with the water depth range of 3 to 9 m around the Seonam. Some rocky areas also appear in the western region. Seafloor backscatter image shows irregular, complex reflection patterns of acoustic intensity mainly in the eastern and western adjacent areas around Seonam, and in the northern and southern coastal waters, which are almost identical to the underwater rock zones with shallow water depth. The detailed bathymetry and seafloor image datasets around Seonam, using the multi-beam echo sounder and the side scan sonar, can be used as an essential data for environment habitat mapping.

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