Baseline Positioning System Research Articles

Error Analysis on Ultra-Short Baseline Positioning System

Aiming at the problem of low accuracy of ultrashort baseline positioning system in practical applications, this paper introduces hydroacoustic channel response error and transducer distortion error, and analyses the influence of each factor on positioning accuracy in the positioning process according to the time delay estimation method. Finally, the major and minor factors are distinguished according to the influence mechanism and the degree of influence of the error factors. The results show that the ship attitude error and hydroacoustic channel error are the main factors affecting the positioning accuracy.

Guided Trajectory Filtering for Challenging Long-Range AUV Navigation

Aiming at the challenging underwater navigation of autonomous underwater vehicle (AUV), this paper develops a novel filtering method with guided trajectory. The relatively low frequency of ultra-short baseline positioning system (USBL) measurement and the noise caused by complex scenes have a significant impact on the accuracy of AUV motion estimation. Although the existing adaptive extended Kalman filter (EKF) and adaptive unscented Kalman filter (UKF) which can roughly eliminate these outliers, the filtering results of these algorithms are not smooth and have the serious degree of the jitter, and then greatly affect the local consistency and quality of topographic map seamless stitching. We exploit the relatively smooth strap-down inertial navigation system (SINS) as the guided trajectory for motion estimation, and propose a trajectory smoothness preserving filter algorithm. This system has the advantage of maintaining local gradient consistency, which not only improves the navigation accuracy, but also ensures the smoothness of the estimation system. Simulation results show that our approach has high robustness and good smoothness. The effectiveness and practicability of the method are demonstrated by real experiments in multiple deep-sea areas with an average depth of more than 1000 meters in the southwest Indian Ocean.

Multi-body modelling and analysis of the motion platform for underwater acoustic dynamic communication

With the development of marine science, the dynamic underwater acoustic network composed of many underwater and surface nodes has become an active research field of information science. The network in this study mainly involves the underwater gliders integrating underwater acoustic transducers and the wave glider carrying an ultra-short baseline positioning system. The attitude change of the underwater glider during zigzag profiling changes the beam pointing of the underwater acoustic transducer, which may lead to communication failure in the network. To deal with this problem, a motion platform for integrating an underwater acoustic transducer is proposed to be installed on the underwater glider. This work first integrates an underwater glider and a wave glider into a multi-body model by taking underwater acoustic signals as the media to illustrate the kinematics of the proposed motion platform. According to screw theory, the motion platform needs at least two rotational degrees of freedom to follow the ultra-short baseline positioning system. According to the bend of the sound ray, the motion angles of the motion platform are modified, and the motion platform controller is designed. The simulation results show that the controller can keep the underwater acoustic transducer tracking and pointing to the ultra-short baseline positioning system during communication when the underwater glider and wave glider move freely.

Accurate two-step filtering for AUV navigation in large deep-sea environment

Underwater navigation is a challenging topic in the field of underwater exploration. Accurate and effective underwater navigation is necessary in applications such as 3D seafloor topography scanning, cable laying, deep-sea resource survey and wreck salvage. However, underwater navigation becomes difficult due to the variability and complexity of underwater environment. In the deep-sea environment, the ultra-short baseline positioning system (USBL) is very unstable, and the flying abnormal points and signal loss often occur. To solve these problems, this paper proposes a two-step filtering scheme combined with doppler velocity log (DVL). The first step is to construct a rough Monte Carlo particle filter (MPF) model for the autonomous underwater vehicle (AUV) position, and then select candidate particles with the strategy of minimizing the local backward dead reckoning (DR) errors. In the second step, the results of the first step are further smoothed and optimized using the weighted extended Kalman filter (WEKF). Finally, the robustness and practicability of the proposed method are verified by the multiple data obtained from several sea trials in the South-West Indian Ocean. The results also show that the integrated navigation framework is superior to single navigation method and other traditional filtering methods. The best balance between accuracy and computational cost is achieved.

The detection method of wrecked plane's black box based on SCOUT+ ultra short baseline positioning system

The black box of wrecked aircraft, as the witness of air disaster, need to be salvaged quickly. In the ocean environment of twenty meters deepth, we search to locate the aircraft black box based on SCOUT+ ultra-short baseline positioning system (USBL). The black box simulator is located in 20 m water depth ocean environment. The positioning accuracy reaches 6.35 m, and the angle positioning accuracy reaches 2.78°. After eliminating the fixed error of installation, the angle positioning accuracy reaches 0.40°. In general, the SCOUT+ detecting accuracy of the black box reaches the expected requirement and meet real needs.

Inverted ultra-short baseline signal design for multi-AUV navigation

Recent years scholars have seen remarkable advancements in Autonomous Underwater Vehicle (AUV) technologies despite limited underwater energy. Multi-AUV positioning technology is an especially popular collaborative research subject; at present, long baseline and ultra-short baseline systems are available for multi-AUV positioning. Long baseline positioning has many disadvantages including overly complex settings and limited effective area for beacon collection.Ultra-short baseline positioning system is rather heavy and allows for fewer users.This paper proposes a new model based on the inverted ultra-short baseline (iUSBL) for AUV positioning. The model accommodates many users, maintains secret positions under deep sea conditions, and functions over lengthy distances, among other advantages. Highly detectable signals are designed for enhanced positioning accuracy in the proposed system. Simulation and anechoic tank experiment results indicate that the direct sequence spread spectrum (DSSS) signal is the optimal transmission signal during the positioning process.

Angular misalignment calibration method for ultra‐short baseline positioning system based on matrix decomposition

For an ultra-short baseline (USBL) positioning system, the angular misalignment between the acoustic array and attitude sensor will introduce overwhelming positioning errors. In order to eliminate this type of errors, a method to calibrate angular misalignment is proposed here. In the method, individual angular misalignment is estimated through the decomposition of the related rotating matrix and overall angular misalignment is calculated using an iterative estimator. Not only does the method determine the angular misalignment more accurately but also it can be applicable to any arbitrary trajectory even the pre-determined trajectory is distorted by the environmental forces (such as winds, currents). The estimation error of the method is analysed through a simulation with different types of trajectories. Its performance is also evaluated in a field experiment. The method is compared with an existing method using both simulated and field data. The simulation and field experiment results indicate that the method has better performance and does improve the positioning accuracy of a USBL system.

Optimal Design of Beacon Array for Long Baseline Positioning System Used in Manned Deep-Sea Submersibles

Ultrashort baseline positioning systems are used to localize manned deep-sea submersibles. A long baseline positioning system is a significant supplement to an ultrashort baseline positioning system and provides more precise positioning. The long baseline beacon array design applied is a primary factor affecting the accuracy of long baseline positioning. However, beacon array designs have mainly been studied in autonomous underwater vehicles (AUVs). Because the characteristics and dive tasks between AUVs and manned deep-sea submersibles are different, the simple beacon array formations used in AUVs cannot be directly used in manned deep-sea submersibles. To the best of our knowledge, this study is the first to present the optimal design of a beacon array for a long baseline positioning system used in manned deep-sea submersibles. In this paper, based on the characteristics of a manned deep-sea submersible, the seven basic principles used for the optimal design of a long baseline beacon array are presented. First, the dive tasks of a JIAOLONG manned deep-sea submersible are analyzed, including the relationship between the dive survey lines, and the depth and distance of each line. Second, we explore the minimum beacon number to cover the dive site and its vicinity. Third, we adjust the beacon position based on the seven optimal design principles. The beacon array is designed to satisfy manned deep-sea submersible dive requirements during the JIAOLONG Test Applications Voyage 2013. A sea trial demonstrates that the long baseline positioning results are reliable if at least three beacons are not blocked, and the accuracy of the long baseline positioning system is better than that of an ultrashort baseline.

A Combined Ray Tracing Method for Improving the Precision of the USBL Positioning System in Smart Ocean.

The ultra-short baseline positioning system (USBL) has the advantages of flexible application and easy installation, and it plays an extremely important role in the underwater positioning and communication. The error of the USBL in underwater positioning is mainly caused by a ranging error due to ray tracing, a phase difference error of the USBL, and acoustic noise in the underwater communication. Most of these errors are related to the changes in the sound speed during its propagation through the ocean. Therefore, when using the USBL for underwater detection, it is necessary to correct the sound speed profile in the detection area and optimize the ray tracing. Taking into account the actual conditions, this paper aims at correcting the model of underwater sound speed propagation and improving the tracking method of sound lines when the marine environment in the shallow sea area changes. This paper proposes a combined ray tracing method that can adaptively determine whether to use the constant sound speed ray tracing method or the equal gradient ray tracing method. The theoretical analysis and simulation results show that the proposed method can effectively reduce the error of slant distance in USBL compared with the traditional acoustic tracking method and the constant sound speed ray tracing method. The proposed sound ray correction algorithm solves the contradiction between the number of iterations and the reduction of positioning error and has engineering application value.

Optimal distance for moving long baseline positioning system with distance-dependent measurement noise

This article investigates the effect of distance-dependent noise on optimal transponder distance in a moving long baseline positioning system. First, according to the positioning model of the moving long baseline positioning system, the relationship between measurement noises and positioning error is established. Second, a cost function is proposed to evaluate the positioning performance. Then, based on the optimal formation, the optimal distance is deduced. Finally, the relationship between the optimal distance and the parameter for the distance-dependent error is proposed. By using this relationship, the effect of distance-dependent measurement noise on optimal distance is analyzed. Simulation examples illustrate the results.

A Precise Positioning Algorithm for Long Baseline Positioning System with Uncertain Sound Speed

Due to its high accuracy and great positioning range, long baseline positioning system has a wide range of application in precise positioning of underwater static objects. In long baseline underwater positioning system, errors due to uncertain sound speed are the major facts to its positioning accuracy. In this paper, a precise positioning model of the long baseline system is established by setting the acoustic signal to propagate at different speeds between the target and different hydrophones, and particle swarm optimization algorithm is used to solve the multi-parameter optimization problem. Presented simulation results show that the proposed algorithm can effectively improve the positioning accuracy of the long baseline positioning system compared to existing algorithms.

Methods of unwrapping phase ambiguity and selecting direct sounds in an ultra short baseline positioning system

This paper presents a novel method to unwrap phase ambiguity and an expert system to select the direct sound from several reflecting pulses in an USBL positioning system. Generally, in the crossed-shaped USBL array, unwrapping ambiguity in the long edge is based on the absence of ambiguity in the short edge, where the array spacing is less than half-wavelength. However, if the positioning system works at a high frequency, which results in the short-edge phase ambiguity, the classical method to unwrap long-edge ambiguity will fail. This paper proposes a sector searching method for this scenario. It utilizes all combinations of two edges to solve all possible target orientations, and takes the mode as the final result. Additionally, hydrophones receive multi-path reflections besides the direct sound in practical application. The expert system is particularly used for selecting the direct sound correctly, which seriously effects the positioning precision. It contains series of criteria to evaluate the quality of each pulse and considers the pulse with the best quality as the direct sound. Simulation and field experiment results prove that the proposed methods are feasible and can achieve good accuracy. Keywords: USBL; phase ambiguity; expert system; and direct sound.

Optimal Distance between Mobile Buoy and Target for Moving Long Baseline Positioning System

This paper investigates the problem of how to design the distance between a mobile buoy and the target to derive maximum positioning accuracy with a Moving Long Baseline (MLBL). To that end, the positioning model and the error sources of MLBL are derived, respectively. It is assumed that the position measurement of the mobile buoy and the distance measurement between the mobile buoy and the target are corrupted by white Gaussian noises, and the variance of the distance measurement is distance-dependent. Using tools from estimation theory, the Positioning Accuracy Metric (PAM) is designed with the distance error and the position errors are considered. Based on the PAM, the optimal distance between the mobile buoy and target is deduced when the mobile buoys are in optimal geometry. Simulation examples illustrate the results.

Research on Signal Aliasing in Long Baseline Positioning System

In the long baseline positioning system, underwater vehicle use transponder reply signals for positioning and navigation, reply signals aliasing is the main reason of inaccurate detection and instability detection. This paper aimed at the problem and research on signal aliasing in long baseline positioning system, theoretical and simulation results show that: Both overlap degree and overlap energy have a certain distribution. The size of signal aliasing area associated with signal overlap degree. The number of signal aliasing is different in different aliasing area. Signal aliasing will affect signal detection, and reduce the long baseline positioning accuracy.

Cooperative Navigation for Multiple AUVs Based on Relative Range Measurements with a Single Leader

his paper deals with the cooperative navigation problem of multiple autonomous underwater vehicles (AUV). A novel method which does not depend on a beacon network like in long baseline positioning system is proposed. The principle of this approach is to realize the cooperative localization of AUVs by using relative range measurements between the leader and the follower vehicles by means of an extended Kalman filter. Simulation results that validate the effectiveness of this approach are presented.

Short baseline positioning with an improved time reversal technique in a multi-path channel

The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system. In this paper, the application of a time reversal mirror to the short baseline positioning system was investigated. The time reversal mirror technique allowed the acoustic signal to better focus in an unknown environment, which effectively reduced the expansion of multi-path acoustic signals as well as improved the signal focusing. The signal-to-noise ratio (SNR) of the time reversal operator greatly increased and could be obtained by ensonifying the water. The technique was less affected by the environment and therefore more applicable to a complex shallow water environment. Numerical simulations and pool experiments were used to demonstrate the efficiency of this technique.

Underwater Docking of AUV with the Dock and Virtual Simulation

To expand the working field of AUV, a kind of underwater docking technology of AUV with the dock is introduced which has an acoustic short baseline positioning system and visual guiding system. The short baseline system can guide the AUV to implement long range navigation. And the visual guiding positioning system can guide the AUV’s underwater close docking. To get intuitive demonstration on surface workstation, the virtual simulation module using creator and Vega Prime software was developed. Through pool experiments, it shows that the docking mode is feasible and the simulation is intuitive, effective.

Description of a Remote Still Photography System for Collection of Benthic Photo-Quadrats

AbstractQuantitative sampling of benthic communities is central to a wide range of ecological research, from understanding spatial distribution and ecology to impact studies. With the need to sample deep as well as shallow regions, limited sampling capabilities of diver-based methods and the expanding footprint of human activity, there is a need for an effective system capable of classifying benthic assemblages and able to monitor potential anthropogenic impacts. Here we describe a remote system capable of collecting benthic photo-quadrats to depths of 100 m. A procedure for the classification of these images into 64 abiotic and biotic categories is also described. During a 64-day sampling program that included sampling at seven locations along 1,200 km of coastline that resulted in the collection of over 9,000 images, only one day of sampling was lost due to equipment malfunction, with 99.5% of points able to be classified to the taxonomic resolution required, demonstrating the reliability and accuracy of this system. Furthermore, the incorporation of differential GPS and ultra-short baseline positioning system allowed collected images to be geo-referenced to within 0.5 m. Such precision allows the system to be used in conjunction with hydroacoustic habitat mapping techniques and potentially for repeated monitoring of areas with a small spatial extent. Development of this system provides a cost-effective means of quantifying benthic assemblages over broad scales.