Key to the classification of unexploded ordnance (UXO) using a subbottom imaging system such as the Buried Object Scanning Sonar (BOSS), is the ability to accurately account for the impacts of the environment on the target response [1,2]. While knowing whether the target is buried in mud or sand is useful, having accurate estimates of the geoacoustic properties of the seabed at the target location has the potential to greatly enhance the efficiency and accuracy of target classification algorithms [3]. Under previous SERDP‐funded projects, a physics‐based inversion algorithm has been developed and applied to sonar data collected by a high‐frequency multibeam echo sounder [4]. The ultimate goal of those efforts has been to develop a technique to make wide‐area surveys of UXO sites and provide maps of sediment properties such as density and sound speed that can be used in planning for the deployment of UXO imaging sonars. While developed using high‐frequency multibeam sonar data, the algorithm itself is sonar agnostic and can potentially be applied to the imaging sonars themselves. The objective of this project is to modify the current implementation of the inversion algorithm such that it can invert sonar data collected by the BOSS, identify any issues with the new implementation that would require a significant scientific/engineering effort to overcome, and determine how best to test and evaluate the BOSS inversion performance.

Using information about the beam patterns, calibration, and operation of the BOSS, the project team plans to modify the existing inversion code‐base, developed under previous SERDP‐funded efforts, such that it can invert the BOSS data for geo‐acoustic parameters. Preliminary evaluations of the inversion performance will be made using existing BOSS datasets collected in Sequim Bay so that the inversion output can be compared to ground truth data also collected under previous SERDP‐funded efforts. This should allow the project team to identify any issues in the transition of the inversion code, determine whether those issues can be resolved with additional engineering or modeling efforts, and determine what additional BOSS data and ground truth data would be required to fully evaluate the BOSS inversion.

Implementing the BOSS‐inversion algorithm will enhance the capabilities of the BOSS without requiring any modification of the sonar or the collection of any additional data beyond what the BOSS is collecting during normal sonar operations. The inversion will provide geoacoustic data directly relevant to the frequencies at which the BOSS operates, collocated with the detected targets, and at greater depths than is possible using high‐frequency multibeam sonars.

1. “SERDP and ESTCP Workshop on Technology Needs for the Characterization, Management, and Remediation of Military Munitions in Underwater Environments,” Final Report, Oct. 2007.
2. “SERDP Workshop on Acoustic Detection and Classification of Munitions in the Underwater Environment,” Final Report, April 2008
3. Kargl, S, “Acoustic Response of Underwater Munitions near a Sediment Interface: Measurement Model Comparisons and Classification Schemes,” Final Report, SERDP Project MR‐2231, April 2015.
4. Hefner, B.T., “Inversion of High Frequency Acoustic Data for Sediment Properties Needed for the Detection and Classification of UXOs,” SERDP Final Report for MR‐2229, May 2015.