Towards Autonomous Operations and Systems in Marine Archaeology
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- Institutt for marin teknikk 
A large part of our common cultural heritage, ranging from submerged prehistoric landscapes to modern steel wrecks, lies on the seabed. For centuries they have remained protected by depth and remoteness, but are now under pressure as our activities in the ocean space are increasing. Sound management of this underwater cultural heritage (UCH), especially in deeper waters, requires enabling methods and technologies for detection, investigation and monitoring. After what oceanographers have called “a century of undersampling”, the marine sciences are now benefiting from tremendous technological advances in sensors and sensor platforms. This thesis looks at how a selection of novel sensors and platforms can be used to improve and develop new methods for marine archaeological surveying. The potential for autonomous operations and systems for marine archaeology will in particular be adressed. Through a series of papers, the properties and capabilities of synthetic aperture sonar (SAS), underwater hyperspectral imager (UHI) and remotely operated vehicle (ROV) based stereo photogrammetry have been explored and applied to various UCH sites. Together they constitute a suite of sensors that can efficiently survey a large area with SAS, classify objects of interest based on spectral fingerprints with UHI, and finally perform detailed recording of archaeological sites with stereo cameras. Efficient exploration of the deep or remote marine environments depends on the use of underwater robotics, particularly untethered autonomous underwater vehicles (AUVs) that can be sent out on missions covering large areas and return with data from multiple sensors. However, for detailed investigations applying close range optical sensors, ROVs are preferable platforms. The resources and ROV pilot skills required for such operations still represent an obstacle for archaeological end users. The thesis discusses possible benefits, challenges and strategies for conducting surveys autonomously. New technology has led to new opportunities for a holistic environmental monitoring approach adjusted to purpose and object of interest. The proposed integrated environmental mapping and monitoring (IEMM) concept, presented in the thesis, describes the different steps in such an approach: from purpose of mission, to selection of parameters, sensors, sensor platforms, data collection, data storage, analysis and data interpretation for reliable decision making. The IEMM concept serves as a basis for a proposed framework for a fully autonomous marine archaeological survey, utilizing the sensors and platforms described in the papers. All sensors and platforms described in the thesis have been tested on actual archaeological materials and sites, both in laboratory and in the field. Experiences from interdisciplinary research cruises have been essential for developing frameworks for integrated operations, data processing and using collected data actively in mission planning and replanning. Theoretical issues concerning implications of new technologies and methods are considerable, and a thorough discussion of these issues is necessary for moving the field towards autonomous operations and systems in marine archaeology. The thesis is edited as a collection of papers.