Ocean currents measurement using an ADCP mounted on an Autonomous Underwater Vehicle

Abstract

2 pages, figuresAutonomous Underwater Vehicles (AUVs) are gradually being adopted by ocean observing systems as versatile platforms for high resolution autonomous underwater sampling. A large variety of sensors can be mounted on these vehicles, allowing for multi-parametric characterization of water masses, seafloor acoustic/optical exploration or any other investigation requiring instrument autonomy, high spatiotemporal data resolution (~1m, 1Hz) in relatively long transects (~30 km) and good underwater positioning accuracy. One of the sensors that is common to most AUVs is the DVL (Doppler Velocity Log), which, mounted facing downward, uses the Doppler Effect to calculate the AUV’s velocity with respect to the ground (i.e. bottom tracking), provided it is within the DVL’s range. This is a key sensor to obtain accurate positioning as the Global Positioning System (GPS) becomes useless underwater. Most DVLs have also the capability to perform as an ADCP (Acoustic Doppler Current Profiler), turning the AUV into a potential ocean currents measurement instrument. However, a lack of standardization, thorough comparison with more assimilated technologies and the added data processing difficulty intrinsic to a 3D moving instrument provoke that, nowadays, one can hardly find oceanographic studies where the currents measurement task relies on autonomous platforms. The speaker will present the results of a field experiment comparing the AUV currents measures with those of a moored AWAC as well as the data processing techniques used to obtain the currents. The main purpose of the talk is to interact with oceanographers in order to comment on the obtained results and also to establish the requirements for an AUV water currents processing tool (Python scripts) that is to be developed soonPeer Reviewe