Path planning for gliders using Regional Ocean Models: Application of Pinzón path planner with the ESEOAT model and the RU27 trans-Atlantic flight data

Unmanned Underwater Vehicles (UUVs) are commonly used in Oceanography due to their relative low cost and wide range of capabilities. Gliders, being UUVs, are particularly suitable for long-range missions because of their large autonomy. They change their buoyancy to dive and climb describing a vertical saw tooth route, which produces an effective but low horizontal speed. This makes them strongly sensitive to ocean currents, and therefore, they might have to adapt the heading to the current field. In this article we outline a new path planning software named Pinzon to assist UUVs piloting, that integrates a novel path planning algorithm called CTS-A* (Constant-Time Surfacing A*). It manages ocean currents provided by Regional Ocean Models (ROMs) that capture their high temporal variability, which affects the vehicle trajectory significantly. This kind of path planning tools are particularly useful for gliders, especially for long-range missions. In this work, we consider a particular region traveled by the RU27 "Scarlet Knight" glider in the trans-Atlantic mission. We focus on the last weeks of the mission, when the glider crossed the Spanish EEZ, from 14°W to 12°W meridian. It is possible to compare the path planner output to that of a direct path to the goal, or even the RU27 path. We have used a ROM provided by the ESEOO project for the Spanish Atlantic shore, known as ESEOAT. It provides ocean currents hourly, which capture the high variability of the currents in the zone. For this reason, daily means or other ocean models are generally unsuitable.