Comparison between the Employment of a Multibeam Echosounder on an Unmanned Surface Vehicle and Traditional Photogrammetry as Techniques for Documentation and Monitoring of Shallow-Water Cultural Heritage Sites: A Case Study in the Bay of Algeciras

Abstract

Over the last few years, due to various climatic, anthropogenic, and environmental factors, a large amount of submerged heritage has been unearthed and exposed to deterioration processes in the Bay of Algeciras. These impacts can be more severe in shallow waters, where the cultural heritage is more vulnerable to natural and human-induced impacts. This makes it urgent to document cultural heritage at risk of disappearing using different techniques whose efficiencies in the archaeological record need to be determined and compared. For this purpose, we have documented a shipwreck in the Bay of Algeciras using two techniques: photogrammetry and a multibeam echosounder. The photogrammetric method consists of obtaining a 3D model from numerous photographs taken of an object or a site. The processing software creates three-dimensional points from two-dimensional points found in the photographs that are equivalent to each other. Multibeam echosounders are capable of providing side scan imagery information in addition to generating contour maps and 3D perspectives of the surveyed area and can be installed in an unmanned surface vehicle. As a result, we have obtained two 3D visualisations of the shipwreck, i.e., digital copies, that are being used both for the analysis of its naval architecture and for its dissemination. Through the comparison of the two techniques, we have concluded that while a multibeam echosounder provides a detailed digital terrain model of the seabed, photogrammetry performed by divers gives the highest resolution data on objects and structures. In conclusion, our results demonstrate the benefits of this combined approach for accurately documenting and monitoring shipwrecks in shallow waters, providing valuable information for conservation and management efforts.

Surveying and monitoring submerged archaeological sites in inland waters through a multiproxy strategy: The case of Dolmen de Guadalperal and other sites from Valdecañas reservoir (Spain)

“…The use of multibeam and SSS techniques for archaeological documentation is well‐documented in marine environments (Gould & Green, 1991; Solana Rubio et al, 2023; Teixeira et al, 2018; Violante, 2020), some of them in Spanish waters (Castillo Belinchón et al, 2012; Higueras‐Milena Castellano & Cerezo Andreo, 2021; Negreruela Martínez et al, 2019), but perhaps not as many experiences in freshwater settings (Janowski et al, 2021; Yang et al, 2020).…”

Testing and Analysis of Selected Navigation Parameters of the GNSS/INS System for USV Path Localization during Inland Hydrographic Surveys

“…Their use is constantly expanding in many areas, and the development of autonomous systems technology enables more and more advanced functions and applications. USVs can be used for a variety of purposes such as archaeological research involving the discovery and examination of sunken ships or plane wrecks [ 13 , 14 ]; biological research enabling the observation of the behaviour of marine animals in their natural environment [ 15 ]; oceanographic research to record data on salinity, sea currents, temperature, topography of the sea and ocean floor [ 16 , 17 ]; monitoring the marine environment by measuring water quality, pollution and vegetation levels, as well as the state of marine ecosystems [ 18 , 19 ]; ocean resource exploration such as gas, mines and oil, as well as offshore pipeline/platform construction and maintenance [ 20 , 21 ]; search and rescue of missing people on waterbodies [ 22 , 23 ]; military applications for defence and security purposes such as monitoring coastal areas; protection of offshore installations; or reconnaissance in hard-to-reach places [ 24 , 25 ].…”

Method of Time Estimation for the Bathymetric Surveys Conducted with a Multi-Beam Echosounder System

“…MBES is widely used in the operations of laying of trans-oceanic telephone cables, exploration and drilling for the oil extraction industry, locating underwater mineral deposits, and learning about Earths geological processes [19][20][21][22]. These swath systems are also successfully used in the study of underwater cultural heritage [23,24].…”