Doppler Velocity Log theory and preliminary considerations for design and construction

Doppler Velocity Logs (DVLs) are devices that have considerable and widespread use in maritime applications. They can be used to provide velocity information, with respect to the sea floor, about the vehicle on which they are mounted. The principle which they use to provide this information is, as their name suggests, the Doppler shifting of acoustic signals. This paper seeks to describe the potential accuracy of a DVL as a function of both design and environmental parameters. It takes a two-stage approach in doing so. The first stage is to find the accuracy of a single acoustic beam based on some particular method (in this case: Non-Linear Least Squares parameter estimation). The second step is to find the resulting accuracy of a multi-beam DVL based on the results acquired in the first step. This paper serves as a precursor to designing and building a “DIY” DVL. It´s intent is to provide information about some of the design decisions required to achieve a certain accuracy. The paper´s methods are more or less independent of the specific methods used in industry, as that information is largely proprietary. The paper is divided in to three parts. The first part is an introduction to the use, capabilities, and functionality of DVLs. The second part concerns the accuracy and simulation of a single acoustic beam of a DVL. The third part discusses the accuracy of a full multibeam configuration as a function of the second.