Heterogeneous Fleets of Active and Passive Floating Sensors for River Studies

Abstract

Lagrangian sensing for tracing hydrodynamic trajectories is an innovative approach for studying estuarial environments. Actuated Lagrangian sensors are capable of avoiding obstacles and navigating when active and retain a passive hydrodynamic profile that is suited for Lagrangian sensing when passive. A heterogeneous fleet of actuated and passive drifting sensors is presented. Data assimilation using a high-performance computing (HPC) cluster that runs the ensemble Kalman filter (EnKF) is an essential component of the estuarial state estimation system. The performance of the mixed capability fleet and the data assimilation backend is evaluated in the context of a landmark 96-unit river study in the Sacramento-San Joaquin Delta region of California. C 2015Wiley Periodicals, Inc.Passive drifters have proved very successful for oceanographic applications, where fixed infrastructure can be impractical to install. A logical extension of the oceanographic research in Lagrangian sensing is to develop sensors for nearshore environments such as rivers and bays. Lagrangian sensors can be used in this context to better monitor the flow of freshwater and the transport of constituents therein. Specific examples include assessing vulnerabilities to contaminant spills or infrastructure failure in Journal of Field Robotics DOI 10.1002/rob Tinka et al.: Heterogeneous Fleets of Active and Passive Floating Sensors • 3 Contributions of this ArticleThis article presents a system-level description of a heterogeneous FSN, including actuated drifters, passive drifters, and communication relays; the description of a field operation to demonstrate system functionality and to validate core assumptions about drifter operations in estuarial environments; an analysis of the utility of the actuation capability of the active component of the fleet; the design and implementation of a back-end data assimilation server cluster; and an analysis of the assimilation system performance and output using the data gathered in these experiments. This experiment represents a significant step in the deployment of autonomous floating robotics systems in unstructured natural environments. To our knowledge, this experiment is the first of its kind in the field of estuarial hydrodynamics Journal of Field Robotics

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