This software addresses the issue of underwater localization of unmanned vehicles and the inherent drift in their onboard sensors. The software gives a 2 to 3 factor of improvement over the state-of-the-art underwater localization algorithms.
The software determines the localization (position, heading) of an AUV (autonomous underwater vehicle) in environments where there is no GPS signal. It accomplishes this using only the commanded position, onboard gyros/accelerometers, and the bathymetry of the bottom provided by an onboard sonar system. The software does not rely on an onboard bathymetry dataset, but instead incrementally determines the position of the AUV while mapping the bottom.
In order to enable long-distance underwater navigation by AUVs, a localization method called ULTRA uses registration of the bathymetry data products produced by the onboard forward-looking sonar system for hazard avoidance during a transit to derive the motion and pose of the AUV in order to correct the DR (dead reckoning) estimates. The registration algorithm uses iterative point matching (IPM) combined with surface interpolation of the Iterative Closest Point (ICP) algorithm. This method was used previously at JPL for onboard unmanned ground vehicle localization, and has been optimized for efficient computational and memory use.
This work was done by Terrance L. Huntsberger of Caltech for NASA’s Jet Propulsion Laboratory.
This software is available for commercial licensing. Please contact Dan Broderick at
This Brief includes a Technical Support Package (TSP).
ULTRA: Underwater Localization for Transit and Reconnaissance Autonomy
(reference NPO-48559) is currently available for download from the TSP library.
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Overview
The document discusses ULTRA (Underwater Localization for Transit and Reconnaissance Autonomy), a localization method developed by NASA's Jet Propulsion Laboratory (JPL) aimed at enhancing the navigation capabilities of Autonomous Underwater Vehicles (AUVs) over long distances. Traditional GPS systems are ineffective underwater, leading to significant localization challenges due to factors such as sensor drift, currents, and low-resolution bathymetric maps.
To address these challenges, ULTRA utilizes an onboard forward-looking sonar system to generate bathymetric data, which is then registered to correct dead reckoning (DR) estimates of the AUV's motion and pose. The registration algorithm combines Zhang’s Iterative Point Matching (IPM) with surface interpolation techniques from the Iterative Closest Point (ICP) algorithm, optimizing for computational efficiency and memory use.
The algorithm operates in two main phases. First, it transforms data points from one sonar dataset based on estimated AUV motion derived from commanded movements and an Inertial Measurement Unit (IMU). Second, it constructs a k-dimensional (k-D) tree for the second dataset to facilitate efficient closest-point computations. The process alternates between finding closest points and estimating transformations between corresponding points, ensuring accurate localization even in the presence of uncertainties in sonar data.
The document also highlights various techniques developed to tackle underwater localization issues, including Long Baseline (LBL) and Ultrashort Baseline (USBL) acoustic transponders for triangulation, as well as terrain-based approaches like particle filters and visual odometry. Most of these methods rely on matching to existing bathymetric databases, which may not always be available onboard the AUV.
Overall, ULTRA represents a significant advancement in underwater navigation technology, enabling AUVs to operate more effectively in GPS-denied environments. The document serves as a technical support package, providing insights into the methodology and potential applications of this innovative localization system, which could have broader implications for various technological, scientific, and commercial fields.
