# Edge Computing Architecture for the Management of Underwater Cultural Heritage
## 4 Buoy System for Underwater Location: A Case Study  
This case study explored the practical implementation of the proposed edge-computing-based architecture for the conservation and management of UCH, specifically focusing on the buoy system designed for accurate underwater location tracking. The ability to precisely track the position of assets such as ROVs, divers, and environmental sensors (among others) is essential for monitoring and protecting submerged sites. However, traditional methods of underwater localisation often face limitations due to poor GPS signal reception underwater and the complexity of marine environments. To address this challenge, a specialised buoy system was developed that integrates acoustic communication technology, GPS, and LoRa-based protocols. This system enables the real-time, accurate localisation of underwater acoustic elements (UAEs) by using edge computing to process data directly at the buoy level, reducing latency and ensuring continuous operation even in areas with intermittent cloud connectivity. By decentralising data processing and utilising advanced communication methods, this solution provides a robust and reliable tool for tracking and managing UCH assets, ensuring better protection and conservation outcomes. The prototype system proposed for underwater localisation was designed in accordance with the specifications of the TECTONIC project [2]. This solution is structured around the main components of the architecture presented before (Figure 1). The elements that comprise the electronic architecture of the buoys are presented in Figure 4:  
A Succorfish Delphi V3 modem (Succorfish Ltd., North Shields, England) [54], along with an acoustic transducer, were essential for facilitating underwater communication, taking charge of generating and analysing the necessary acoustic signals for this purpose. This modem acted as a gateway between serial communication and acoustic communication. For serial communication with an external device, it had an RS232 interface, ensuring the transmitted data's integrity, effectively protecting them from noise and possible interference. The Nordic uC PCB, developed by the research group LABUST (Laboratory for Underwater Systems and Technologies - LABUST, Zagreb, Croatia) [55], integrated the Nordic nRF52840 microcontroller (Nordic Semiconductor ASA, Trondheim, Norway) and was responsible for the communication between the acoustic modem and the ESP32 + LoRa board (Soldered Electronics, Osijek, Croatia), as well as for the voltage regulation for the electronic components. The ESP32 + LoRa board, from e-radonica (now Soldered Electronics [56]), featured an ESP32-WROOM-32D microcontroller (Espressif Systems Co., Ltd., Shanghai, China) that supported WiFi and Bluetooth and had an embedded LoRa module for long-distance transmissions. Communication with the GPS module and with the Nordic microcontroller board was carried out via UART serial buses and with the LoRa module through SPI. An Adafruit Ultimate GPS module [57] was included, providing location, speed, and time data in real time through satellite tracking. It communicated with the ESP32 microcontroller via UART. For a robust and reliable power supply, Li-Ion 18650 battery systems were used in parallel, achieving a total capacity of 7500 mAh and 3.7 V. This ensures uninterrupted operation, even in challenging conditions. Additionally, a waterproof power switch from Blue Robotics added a layer of control without compromising the system's waterproofness. This set of electronic components, encapsulated in the buoys (Figure 5), was crucial in developing and validating the prototype. Field tests were conducted in Lake Jarun in Zagreb, Croatia, on 24 August 2023. During these tests, a system comprising three buoys and an underwater acoustic element (UAE) was deployed to evaluate the system's performance.