Multipulse acoustic mapping system

Abstract

A concept of a novel seafloor surveying and mapping system is described. The system consists of a pencillike, narrow‐beam transmitter and a fanlike, broadbeam receiver. The transmitter beam is sequentially scanning a certain angular sector situated within the receiver beam coverage. For the selected angular directions of the transmitter beam, a pulse is transmitted in these directions. The last pulse is transmitted before the echo due to the first transmitted pulse is received. To avoid ambiguity, it is assumed that the profiled surface is such that the echo due to an earlier transmission always arrives before the echo due to the consecutive transmission. The bottom profile can be calculated by measuring delay times of the successive echoes. Bottom mapping is accomplished by successive profiles obtained along the ship track. The system can be used for high‐speed, high‐resolution mapping of bottoms with complex topography such as encountered in channels, rivers, and harbors. Suitably oriented, the system can also be used to profile shapes of underwater objects (such as icebergs). A sample system configuration is described and its performance discussed. Possible variations of the system to improve its performance are proposed. The concept described represents, a significant improvement over existing solutions to high‐resolution bottom mapping in terms of its relative simplicity, low cost, and performance.

Keywords:

• acoustic mapping
• acoustic surveying
• multibeam bathymetry
• swath system