Predicting the impact of seabed uncertainty and variability on propagation uncertainty

Uncertainty in seabed properties can lead to substantial uncertainties in acoustic propagation, of order tens of dBs. During this project, substantial progress was made in 1) quantifying seabed uncertainties, by developing an advanced seabed measurement technique and powerful commensurate methods to estimate the uncertainties and 2) predicting the effect of those effects on propagation by development of a theory that illuminates the effects of seabed variability and uncertainty on propagation uncertainty. INTRODUCTION Uncertainties in acoustic performance prediction lead to the inability of the Fleet to make judicious decisions about tactics and employment of resources. Seabed variability is one environmental condition that leads to prediction uncertainty. As an example of the importance of the seabed in performance prediction, consider the results of [1] where TL predictions (from existing water column and seabed databases) showed biases of order tens of dB with respect to measurements. Most of these errors were traced to limitations in the present generation of seabed databases; water column databases were relatively robust. This is not to say that the seabed databases are poor everywhere; it is simply to underscore the point that 1) knowing the seabed properties is critical to naval operations involving passive (or active) sonar: tens of dBs are at stake and 2) the ability of the community (6.1 -6.4) to capture seabed properties and associated spatial variability is still quite limited. The Quantifying, Predicting, and Exploiting (QPE) Uncertainty DRI has as its fundamental tenet that in any strategic situation, environmental parameters will never be known in sufficient detail to enable a perfectly accurate acoustic prediction. Thus, the goal is to provide the machinery to be able to quantify the uncertainty associated with that prediction. The focus in this research was the impact of the seabed on propagation uncertainty. LONG TERM GOAL Develop capability for quantifying, predicting and exploiting (QPE) the impact of seabed uncertainty on sonar system performance.