# Underwater Excavation Records Using Underwater Acoustic Survey: A Case Study in South Korea
###### Abstract  
The most effective method for surveying underwater archeological sites is visually identifying areas with relics or remains through diving surveys. However, during underwater excavations, it is difficult to obtain images in turbid water. Furthermore, on-site diving is costly and time-consuming. Marine acoustic geophysical survey equipment is not significantly affected by underwater turbidity, and underwater excavations often rely on geophysical equipment for surface inspections. This study aimed to improve existing underwater excavation imaging through the application of acoustic survey methods. Underwater surveys were conducted via acoustic marine geophysical survey devices at three historically significant underwater sites in South Korea: Dangampo, Nakwoldo Island, and the Battle of Myeongnyang. At the Dangampo site, surveys were conducted using three different sonar devices--side scan sonar, multibeam echo sounder, and scanning sonar--and the results were compared; scanning sonar was the most effective. The methodology was further refined during excavations at the Nakwoldo and Myeongnyang sites. Results show that the scanning sonar can produce images that are more accurate than on-site drawings produced during underwater excavations, even in turbid underwater environments. Moreover, applied in conjunction with high-frequency geophysical exploration techniques, scanning sonar can significantly increase the reliability of investigations of buried underwater remains and relics. marie geophysical survey; sonar; multibeam echo sounder +
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ship sank in 1797 in Bantry Bay, Ireland [10; 11; 12; 13]. The purpose of the investigation was to accurately relocate the wreck, determine the extent of the site, map the seabed and underground surface rocks around the wreck, and provide a base map for a more detailed diver investigation. [PERSON] et al. [14] and [PERSON] et al. [15] also applied geophysical methods to underwater archaeology. In addition, [PERSON] et al. [16] and [PERSON] et al. [17] used sonar equipment to measure the 3D geometric shapes of sunken ships and underwater iron artifacts. [PERSON] et al. [18] conducted a resolution analysis using a variety of sonar systems, including a side scan sonar (SiSS) and underwater acoustic exploration equipment on the same target. [PERSON] et al. [19] described the application of sonar, laser, optics, and other sensor-based technologies that capture ground, intertidal, subsea, and sub-segment deposits in 3D and high resolution, while [PERSON] et al., [PERSON] et al. [20] generated 2D data as 3D data using a commercial 2D Chirp SBP system with a newly designed recording system(Daejeon, Korea) at the site where an ancient wooden shipw was buried, and the ancient shipw was successfully imaged through 3D rendering. [PERSON] et al. [21] conducted comparative studies on traditional underwater survey methods in the Aegean Sea by comparing the results to those derived through the application of the latest techniques in geophysical exploration. These studies highlight the importance of promoting technological advancements in geophysical survey methods and investigating their applicability to excavation surveys of buried cultural relics. This study aimed to upgrade the current survey imaging methodology by applying MGS techniques to underwater excavation (UE) and enhancing the utility of MGS devices in the field of underwater archaeology. To achieve these objectives, we compared the performances of three different MGS systems using data collected in the waters off Dangampo, Taean County (hereinafter the \"Dangampo site\") in 2017. Furthermore, we determined the method best suited for scanning sonar (SS) image mapping based on geophysical surveys at two UE sites, one in the waters off Nakwol Island, Yeonggwang County (hereinafter \"Nakwoldo site\"), and the other at site of the Battle of Myeongnyang near Jindo (hereinafter \"Myeongnyang site\"). These surveys were conducted in 2018 and 2019, respectively.