The performance of bathymetric measurements by traditional methods (using manned vessels) in ultra-shallow waters, i.e., lakes, rivers, and sea beaches with a depth of less than 1 m, is often difficult or, in many cases, impossible due to problems related to safe vessel maneuvering. For this reason, the use of shallow draft hydrographic Unmanned Surface Vessels (USV) appears to provide a promising alternative method for performing such bathymetric measurements. This article describes the modernisation of a USV to switch from manual to automatic mode, and presents a preliminary study aimed at assessing the suitability of a popular autopilot commonly used in Unmanned Aerial Vehicles (UAV), and a low-cost multi-Global Navigation Satellite System (GNSS) receiver cooperating with it, for performing bathymetric measurements in automated mode, which involves independent movement along a specified route (hydrographic sounding profiles). The cross track error (XTE) variable, i.e., the distance determined between a USV’s position and the sounding profile, measured transversely to the course, was adopted as the measure of automatic control precision. Moreover, the XTE value was statistically assessed in the publication.

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Apart from extensive infrastructure protection, modern yacht ports should primarily provide vessels with navigational safety associated with their maneuvering on the approach fairway, as well as mooring in the port aquatory. For this reason, yachts entering the harbor should have up-to-date, accurate, and reliable charts of the port and its surroundings. This article presents hydrographic surveys conducted in the National Sailing Centre (NSC) yacht port at the Gdańsk University of Physical Education and Sport (GUPES), whose aim was to define and develop unique bathymetric and navigational charts of the harbor and the approach fairway. These can be used for example to manage berths in the marina or inform about the depths in the yacht port and on the approach fairway. The chart of the NSC-GUPES and its approach fairway is Poland’s first cartographic image of a harbor, performed entirely on the basis of surveys conducted by an Unmanned Surface Vehicle (USV). The study results demonstrated that the use of a small-sized USV in bathymetric measurements of yacht ports and marinas was significantly more effective than the traditional (manned) hydrographic surveys. Such vessels allow measurements to be carried out in hard-to-reach locations, even between mooring vessels, and in the immediate vicinity of quays. Thanks to the implemented automatic mode of steering on sounding profiles, USVs are equally efficient and capable of carrying out hydrographic surveys on a larger waterbody, i.e., the approach fairway.

In acoustics, the analysis of pressure distribution in a field of surface sources is most frequently performed using the assumption that the source constitutes a part of an infinite planar rigid baffle (Rayleigh’s approximation). However, in many practical cases of ultrasonic echography, assumption of a soft pressure-release baffle (the Rayleigh-Sommerfeld approximation) or of free-field conditions (the Kirchhoff approximation) seemed to be better matched to real conditions. A theoretical survey of the planar baffles problem is given in this paper, and its practical aspects in acoustic source radiation are discussed. Some experiments, showing the influence of different boundary conditions onto radiation patterns, verify the theoretical predictions.

Acoustic diffraction of plane impulsive waves is considered for free-field, baffled, and pressure release boundary conditions, in the case of an arbitrary spatial distribution of combined, amplitude-time delay modulation in an aperture. The method is based on the impulse response analysis of parallel aperture lines, the line impulse responses being then integrated to give an aperture impulse response. A closed-form, analytical expression is derived for lines having an arbitrary amplitude modulation. In the case ofnonmodulated apertures of an arbitrary shape, the aperture impulse response is also of an analytical form, directly involving the aperture contour line. The analysis is performed with emphasis on maintaining clear physical sense of successive evaluation steps.