Protocols for calibrating multibeam sonar

Abstract

Development of protocols for calibrating multibeam sonar by means of the standard-target method is documented. Particular systems used in the development work included three that provide the water-column signals, namely the SIMRAD SM2000/90-and 200-kHz sonars and RESON SeaBat 8101 sonar, with operating frequency of 240 kHz. Two facilities were instrumented specifically for the work: a sea well at the Woods Hole Oceanographic Institution and a large, indoor freshwater tank at the University of New Hampshire. Methods for measuring the transfer characteristics of each sonar, with transducers attached, are described and illustrated with measurement results. The principal results, however, are the protocols themselves. These are elaborated for positioning the target, choosing the receiver gain function, quantifying the system stability, mapping the directionality in the plane of the receiving array and in the plane normal to the central axis, measuring the directionality of individual beams, and measuring the nearfield response. General preparations for calibrating multibeam sonars and a method for measuring the receiver response electronically are outlined. Advantages of multibeam sonar calibration and outstanding problems, such as that of validation of the performance of multibeam sonars as configured for use, are mentioned.

Waves of agitation inside anchovy schools observed with multibeam sonar: a way to transmit information in response to predation

“…Multibeam, omnidirectional sonar allowed dynamic observations and was used to display reactions of schools to predation (Misund, 1993;Nøttestad and Axelsen, 1999;Brehmer, 2004). Recently, new acoustic instrumentation has allowed better description of school internal structures in 2D and 3D Mayer et al, 2002;Foote et al, 2005; see Reid, 2000, for a synthesis), and their evolution through time (Misund and Coetzee, 2000;Axelsen et al, 2001;Misund et al, 2005). Applying such tools to tropical clupeids, it has been shown that in many cases, a school's external morphology is liable to vary greatly while the internal structure remains unchanged (Gerlotto et al, 2004).…”

Convergence and divergence between two multibeam sonars (SIMRAD SM20 and RESON SeaBat 6012) used to extract the spatial, morphologic and energy parameters of fish schools

“…For both sonars, the third dimension was obtained from the succession of pings along the vessel course. Both sonars were manufacturer-calibrated, and checked before the survey using known targets, but they were not calibrated in situ due to the difficulty of carrying out the procedure recommended by Foote et al (2005) and Melvin et al (2003) in the field. The acoustic survey was conducted during daylight on September 23, 2008 along transects of the northern part of the lake, using a protocol described in Guillard et al (2006a) designed to optimize the probability of encountering fish schools during the experiment.…”

Calibrating Multibeam Sonar by the Standard-Target Method: Extending Limited Measurements

“…1 [6,14]. A 60-mm-diameter sphere of aluminum was used as the standard target, its target strength having been determined by intercalibration against another standard target whose material properties were better known.…”

“…Applications have included, for example, observation of fish behavior due to passage of acoustic surveying vessels or pelagic trawls, measurement of swimming speed, study of predator-prey interactions, measurement of bubble populations and particulate concentrations near hydrothermal vents, with references given in [6].…”

“…The standard-target method, which is widely used for the calibration of scientific echo sounders [7,8], has been adapted [6,9], with seminal publications at Oceans Conference forums [10][11][12][13][14].…”