On-Site Calibration-Based Estimation Method of Forward Seabed Elevation Using Forward Scan Sonar

Abstract

This paper addresses a novel calibration based estimation method to measure the forward seabed elevation (FSE) where an area illuminated by forward scan sonar (FSS) for unmanned underwater vehicles (UUVs).The conventional method measures the FSE using one or two down-facing single-beam sonars; this method can, however, cause errors. In order to accurately measure the FSE, a sensor capable of measuring the two-dimensional space of the seabed is needed, such as FSS. The method proposed in this work consists in estimating the FSE by analyzing the acoustic beam distribution characteristics of FSS. A novel FSS beam distribution model is proposed, which simplifies beam distribution characteristics. Then, on-site calibration is conducted to estimate the parameters of this model. Based on the estimated model, templates can be generated and compared with FSS data acquired at the experiment in order to estimate geometrical information at the FSE. The FSE of the best matched template is the estimated FSE of the FSS data acquired in the experiment. In order to verify the performance of the proposed method, experiments using an UUV were carried out in an indoor water tank. We also verified that the proposed method performed well even when there were objects on the seabed.Index Terms-On-site calibration, Modeling of forward scan sonar, Localization of UUV, Forward seabed elevation.

Evaluation of Node-Metastasis in Sparse Underwater Acoustic Sensor Networks for Localization Under Acoustically Stratified Malicious Node Conditions

“…• Proposed method called Compressed-Sensing Malicious-node Compensation (abbreviated as CS-MC) • Triangulation method (abbreviated as C-TOL) [25] • Forward Scan Sonar-Forward Seabed Elevation estimation technique (abbreviated as FSS-FSE) [7] • Fusion of unscented Kalman filter and Linear Kalman filter for joint estimation of target (abbreviated as UL-KF fusion) [5] Triangulation method [25] uses the concept of triangulation uncertainty to determine the localization error of estimated position. FSS-FSE technique [7] uses an acoustic approach in the form of Sonar Scan readings in the two dimensional underwater domain to estimate the distribution of seabed elevation. UL-KF algorithm [5] jointly estimates underwater positioning as well as sea drift with the fusion of Kalman filter in positioning as well as sea drift with the fusion of Kalman filter in case of multiple ranging.…”

“…There are certain challenges and issues in UASN Localization. In [7], underwater measurements are being taken by forward calibration based estimation method. While 2D measurements reduce error, a new beam distribution model is formulated to simplify beam distribution characteristics.…”