# ENDURUNS: An Integrated and Flexible Approach for Seabed Survey Through Autonomous Mobile Vehicles
## 1 Introduction  
The oceans cover more than two-thirds of our planet, representing the vastest part of natural resources available to us [1]. Yet, only a fraction of the total ocean interior has been explored so far [2; 3]. The exploitation of the available ocean resources has been predominantly associated with fishing, tourism, and offshore oil and gas production and, although limited, activity ongoing in mining or other sectors of significant industrial and societal interest [3; 4]. There is growing demand for technological improvement in ocean exploration and monitoring to increase our understanding of the ocean interior for a valuable number of scientific, industrial, and political reasons [5]. Deep water exploration and new data collection in this domain are of special interest to provide new insights into a variety of geological and ecological processes [3]. For instance, there has been relevant industrial effort spent into deep water hydrocarbons exploration [6], offshore carbon capture and storage [7; 8], exploitation of deep-sea mineral resources, or seafloor fibre-optic cables positioning for telecommunications purposes, as well as for seafloor observatories [9; 10]. At the same time, political drivers push toward the implementation of new coordinated marine monitoring programmes for establishing, preserving and restoring relevant Marine Protected Areas as stated in the EU Marine Strategy Framework Directive (2008/56/EC). To satisfy all interests in marine observation, better mapping resolution is needed to increase data accuracy for geohazard analysis (e.g., landslides, fluid escape features, mobile substrates), environmental impact assessments and monitoring (e.g., leaking hydrocarbons/CO\({}_{2}\) and repeated monitoring of benthic habitats and ecosystems to protect marine biodiversity). In such context it is indicative that the General Bathymetric Chart of Oceans (GEBCO) [11] operating under the auspices of the International Hydrographic Organization (IHO) [12] and the Intergovernmental Oceanographic Commission (IOC) of UNESCO [13] has set the objective to promote international collaboration for facilitating the complete mapping of the ocean floor by 2030, under the \"Seabed 2030\" initiative [11]. The primary goal of the \"Seabed 2030\" international initiative is the acquisition of ocean floor data into a high quality 100m-resolution digital model with vast geographic coverage, as compared to older 5 km-resolution data collected in past mapping expeditions [11]. Charting the oceans and evaluating their resources is of great importance also to global economy and societal security since it provides direct information to generate more reliable climate-change models a sustainable food production chain, understand quality and status of sea habitats or explore new offshore energy and mining resources [14]. Many monitoring systems were investigated, developed, and tested in recent decades [9; 15; 16; 17]. A wide state of the art was reported on platforms and instruments used for integrated underwater autonomous mapping and monitoring, at different spatial and temporal scales [15]. Fixed platforms,for example, cabled fixed observatories, oceanographic moorings and landers have been configured as a network of spatially distributed nodes covering an extended area and capable of acquiring data for long time periods (e.g., 10 years) at very high frequency (e.g., 1 Hz) [18, 19]. Nevertheless, the nodes geometry is difficult to change and the infrastructure maintenance results expensive. On the other hand mobile platforms e.g., Autonomous Underwater Vehicles (AUVs) and sea gliders [14, 20, 21] have a higher spatial resolution and coverage, but smaller temporal resolution and coverage. The time and space dimension affect both surveying applications, design and operational requirements of oceanographic instruments and platforms [15]. For example, sea gliders are not suitable for carrying out seabed mapping or to perform inspection of offshore infrastructure, due to their typical vertical shoot-saw trajectories.