On-the-fly Locata/inertial navigation system integration for precise maritime application

Abstract

The application of Global Navigation Satellite System (GNSS) technology has meant that marine navigators have greater access to a more consistent and accurate positioning capability than ever before. However, GNSS may not be able to meet all emerging navigation performance requirements for maritime applications with respect to service robustness, accuracy, integrity and availability. In particular, applications in port areas (for example automated docking) and in constricted waterways, have very stringent performance requirements. Even when an integrated inertial navigation system (INS)/GNSS device is used there may still be performance gaps. GNSS signals are easily blocked or interfered with, and sometimes the satellite geometry may not be good enough for high accuracy and high reliability applications. Furthermore, the INS accuracy degrades rapidly during GNSS outages. This paper investigates the use of a portable ground-based positioning system, known as ‘Locata’, which was integrated with an INS, to provide accurate navigation in a marine environment without reliance on GNSS signals. An ‘on-the-fly’ Locata resolution algorithm that takes advantage of geometry change via an extended Kalman filter is proposed in this paper. Single-differenced Locata carrier phase measurements are utilized to achieve accurate and reliable solutions. A ‘loosely coupled’ decentralized Locata/INS integration architecture based on the Kalman filter is used for data processing. In order to evaluate the system performance, a field trial was conducted on Sydney Harbour. A Locata network consisting of eight Locata transmitters was set up near the Sydney Harbour Bridge. The experiment demonstrated that the Locata on-the-fly (OTF) algorithm is effective and can improve the system accuracy in comparison with the conventional ‘known point initialization’ (KPI) method. After the OTF and KPI comparison, the OTF Locata/INS integration is then assessed further and its performance improvement on both stand-alone OTF Locata and INS is shown. The Locata/INS integration can achieve centimetre-level accuracy for position solutions, and centimetre-per-second accuracy for velocity determination.

Optimal Data Fusion Algorithm for Navigation Using Triple Integration of PPP-GNSS, INS, and Terrestrial Ranging System

“…Similar as GNSS positioning, the TD measurement noise will be increased by a factor of 2 , which can be mitigated by filtering [26]. The Locata ambiguities are assumed to be floating-point values.…”

“…The Locata ambiguities are assumed to be floating-point values. Since the motion of the Locata rover provides the spatial diversity in the measurements, Locata "on-the-fly" ambiguity resolution algorithm is used to estimate the ambiguities on an epoch-by-epoch basis [26]. Thus the unknown variables in the Locata function are user positional parameters and the real-valued carrier phase ambiguities, which can be estimated for the Locata rover on an epoch-by-epoch basis using a Kalman filter estimator.…”

Dynamic Lever Arm Error Compensation of POS Used for Airborne Earth Observation

“…Besides, the lever arm between the IMU and odometer is also taken into account for the land-vehicle navigation system in [15]. The lever arm between the Locata antenna and IMU is compensated for the Locata/SINS-integrated system in [16]. In the application of transfer alignment, the lever arm effects among master IMU and slave IMUs are analyzed and compensated in [17][18][19].…”

Locata Network Design and Reliability Analysis for Harbour Positioning

“…Since 2002, Locata technology has been investigated for its feasibility as an alternative ground-based positioning technology. The fundamentals of the Locata technology and some results of consecutive tests, for different applications have been reported in the literature (e.g., Barnes et al, 2003Barnes et al, , 2004Choudhury et al, 2009;Li and Rizos 2010;Montillet et al, 2009;Rizos et al, 2010;Jiang et al, 2013). In these papers the feasibility of Locata technology for various environments have been investigated, including using Locata technology for indoor precise positioning, for bridge deformation monitoring, to achieve sub-centimetre level error of a Locata rover's position through static and kinematic tests, or to realise precise positioning in urban canyons.…”