OLB: An Open Lora Buoy for Coastal Water Measurements

TL;DR

OLB addresses the need for affordable, open-source coastal ocean measurements by providing a LoRa-based drifter buoy framework consisting of buoy, base station, and data platform. The design emphasizes modular hardware and software, enabling remote updates and sensor expansion, while maintaining low power operation for multi-month deployments. Validation shows LoRa range up to around 2 km in typical coastal conditions and a battery life exceeding several months, with a live Drammensfjord deployment achieving up to 5.3 km ranges and partial recovery of trajectories. The work demonstrates the practicality and cost-effectiveness of open-source ocean instrumentation for model validation, coastal monitoring, and data-driven oceanography.

Abstract

Oceanographic instrumentation technology is currently under rapid transition towards increasingly open-source technology. Open-source buoys compete with commercial and closed-source buoys both in price, functionality and availability. Long-range radio (LoRa) is a communication technology which is inexpensive both in terms of data transfer cost and power without the need for pre-existing infrastructure. In this paper, we present OLB, an open-source drifter buoy using LoRa for coastal water measurements. OLB is designed to be reliable, low-cost, modifiable and power efficient. We present validation experiments demonstrating that OLB can achieve a radio telemetry range of more than 2 kilometres, and has an expected battery lifetime of up to seven months. Finally, we discuss the role and contribution of OLB in the space of open-source instrumentation and ocean modelling.

Figures (9)

• Figure 1: Relationship diagram showing how the different parts of the OLB framework interact. Drifters are deployed in a coastal area within range of one or more base stations. They gather in situ measurements, which are sent via LoRa to a base station, which then bundles the data and sends them to the backend data platform over GSM. Conversely, the data pipeline allows the user to remotely give instructions to both the base stations and the drifters by sending instructions from the backend data platform to the base stations, and from there to the buoys.
• Figure 2: Subfigure (A) shows a schematic for the wiring between each component on the OLB buoy. The reed switch enables the user to turn off the buoy by placing a magnet on a designated spot on the buoy casing. The pull-down resistance between the EN-pin on the GPS and ground is to ensure that the GPS is switched off while not measuring. A small coin cell battery is connected to the GPS to allow it to store fix information even when powered off. Subfigure (B) shows the corresponding printed circuit board (PCB), where the connections depicted in Subfigure (A) are implemented.
• Figure 3: An assembled OLB buoy in a container with a PCB (subfigure A), and the inside of the buoy (subfigure B). Subfigure (C) shows the buoy alongside a female Anas platyrhynchos (mallard duck) near Sognsvann, Oslo.
• Figure 4: The wire schematic for the base station [Subfigure (A)] and the corresponding PCB layout [Subfigure (B)]. The Wio-E5 Mini board acts as the radio transceiver and main control unit. The system operates on 5V logic, and can be reset remotely from the notecarrier.
• Figure 5: Radio protocol between base station and buoy. The protocol is separated into three stages. The base station is, when not busy, regularly sending out a short message notifying buoys in the area that it is available for data reception. Once a buoy is ready to transmit, it will turn on the radio to listen mode and check if it gets a signal from a base station. If so, the buoy and the base station will perform a handshake to ensure that the connection is stable and to avoid multiple buoys transmitting simultaneously. Once verified, the base station enters listening mode while the buoy transmits as much data as possible within the time allotted to it by the base station. Finally, the buoy sends a message confirming it is done to the base station before switching to listening mode. If received, the base station might send updated directives to the buoy.