Optimal Reference Nodes Deployment for Positioning Seafloor Anchor Nodes

TL;DR

This paper proposes an optimal deployment strategy for reference nodes in 3D underwater positioning, considering sound speed variability, and validates it through simulations and sea trials.

Contribution

It introduces a novel semi-closed form solution for optimal reference node deployment in 3D underwater TOA localization considering sound speed variability.

Findings

Optimal deployment reduces localization error.

Simulation and sea trial results confirm theoretical predictions.

Method improves accuracy of underwater anchor node positioning.

Abstract

Seafloor anchor nodes, which form a geodetic network, are designed to provide surface and underwater users with positioning, navigation and timing (PNT) services. Due to the non-uniform distribution of underwater sound speed, accurate positioning of underwater anchor nodes is a challenge work. Traditional anchor node positioning typically uses cross or circular shapes, however, how to optimize the deployment of reference nodes for positioning underwater anchor nodes considering the variability of sound speed has not yet been studied. This paper focuses on the optimal reference nodes deployment strategies for time--of--arrival (TOA) localization in the three-dimensional (3D) underwater space. We adopt the criterion that minimizing the trace of the inverse Fisher information matrix (FIM) to determine optimal reference nodes deployment with Gaussian measurement noise, which is positive related to the signal propagation path. A comprehensive analysis of optimal reference-target geometries is provided in the general circumstance with no restriction on the number of reference nodes, elevation angle and reference-target range. A new semi-closed form solution is found to detemine the optimal geometries. To demonstrate the findings in this paper, we conducted both simulations and sea trials on underwater anchor node positioning. Both the simulation and experiment results are consistent with theoretical analysis.