A visualization-based post-processing system for analysis of acoustic data

Socha, David

doi:10.1006/jmsc.1996.0045

Cited by 14 publications

(8 citation statements)

References 8 publications

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“…Methods related to these two have been tried earlier (Socha et al, 1996;Korneliussen, 1999;Higginbottom et al, 2000) but there is still a need to optimize the extraction of information for practical use on large-scale surveys. More effort should be allocated now to improving echosounder systems and transducer platforms to make the multi-frequency observations better suited for combination into synthetic combinedfrequency echograms on the post-processing side.…”

Section: Multi-frequency Data Processing Methodsmentioning

confidence: 98%

“…Most of the available systems were originally intended for either s(f) analysis, or sequential analysis of several frequencies, although a few examples designed for the combined analysis of two frequencies have recently appeared (Socha et al, 1996;Higginbottom et al, 2000). In some systems, layer lines and parameters for scrutiny, which are selected during s(f) analysis, can be transferred readily between echograms along the survey track .…”

Section: Introductionmentioning

confidence: 98%

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An operational system for processing and visualizing multi-frequency acoustic data

Korneliussen

2002

ICES Journal of Marine Science

129

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2002. An operational system for processing and visualizing multi-frequency acoustic data. -ICES Journal of Marine Science, 159: 293-313.Calibrated and digitized data from two or more discrete echosounder frequencies can be combined for the purpose of separating and extracting the acoustic scattering from zooplankton and fish in mixed recordings. This method is also useful for quantifying the relative contribution of each frequency to the total acoustic-backscattering when scrutinizing records in large-scale, acoustic surveys. Echosounder hardware requirements are defined which would permit the ideal extraction of such information. These include calibration, transducer specification, pulse resolution and digital representation of the signals. During this initial study a special version of the Simrad EK500 multi-frequency, split-beam echosounder and the Bergen Echo Integrator (BEI) post-processing system were used. The echosounder transmitted pulses simultaneously at four frequencies, 18, 38, 120 and 200 kHz and transferred the received signals to the post-processing system in calibrated, raw, digitized format. Methods are described for echogram manipulation and for the construction of new, synthetic, combinedfrequency [c(f)] echograms. Examples of extracted scattering information from mixed layers of fish and small scattering-organisms, such as copepods and euphausiids, are shown, and the potential of the method is discussed.

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Section: Multi-frequency Data Processing Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

An operational system for processing and visualizing multi-frequency acoustic data

Korneliussen

2002

ICES Journal of Marine Science

129

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“…Euphausia superba. Survey start and end times distance run on transect (1996) which was implemented via a (length, km), and overall area covered by each survey (km2) in 1994 series of customised Application Visuware (Watkins et al 1995), and was alization System modules (Socha et al 1996). Further signal post-processing was also required to counter the effects software encOuntered in version 3.01 of the EK500 soft- relationships are often expressed in terms of target length (Foote 1987).…”

Section: Methodsmentioning

confidence: 99%

Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity

Brierley¹,

Watkins²

1996

Mar. Ecol. Prog. Ser.

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Dual frequency (38 and 120 kHz) acoustic surveys of shelf-break regions in the vicinity of the Willis Islands, South Georgia, and Coronation Island, South Orkneys, both in the Atlantic sector of the Southern Ocean, were carried out from RRS 'James Clark Ross' dunng January 1994. The difference in echo signal strength between the 2 frequencies [FMVBS (mean volume backscattering strength) = MVBS 120 kHz-MVBS 38 kHzj was used to partition acoustic targets into 3 biological categories: Antarctic krill Euphausia superba, nekton (larger than krill) and zooplankton (smaller than krill). Krill density estimates were derived for both survey areas, and the relative contribution of each class of target to overall regional pelagic biomass determined. Krill distribution in both regions was extremely patchy, resulting in a highly skewed frequency distribution of density; for example one echointegration interval contained 104 times the mean krill density. An approximate 6-fold difference in mean krill abundance was detected between the 2 areas but, in comparison with previously published density estimates, krill densities in both regions were extremely low (1.7 and 10.7 gm-' for Willis and Coronation Islands respectively). Gross regional differences in pelagic fauna1 composition were apparent from inspection of echo charts, and were quantified by detailed analysis of acoustic signals. The water column in the vicinity of the Willis lslands was characterised by a series of diffuse but continuous scattering layers visible only at 120 kHz, and 73% by mass of acoustic targets in this region were classified as zooplankton. In marked contrast, the Coronation Island region was dominated by dense, discrete acoustic target patches which were classified as larger, nektonic, sound scatterers (fish or squid), and only 1 2 % of targets there were classified as zooplankton Elsewhere, data from predator diet analyses carried out at Bird Island, South Georgia, dunng the same season that our acoustic measurements were made, confirm the profoundly low levels of knll availab~lity there and support the acoustic observation that the Willis Islands region contained large numbers of small zooplankton such as the amphipod Themisto gaudichaudii. Similarly, available data on analyses of stomach contents of Chinstrap penguins nesting in a neighbouring region within an oceanographic setting similar to that of Coronation Island reveal the presence of more fish in the diet than usual. Conclusions drawn from acoustic observations as to the relative regional composition of pelagic biomass are therefore clearly supported by independent evidence gathered from predators, and the value of integrating predator/ prey and acoustic studies to characterise the content of localised marine ecosystems is demonstrated. KEY WORDS: Antarctic krill Euphausia superba. Dual frequency acoustic survey. Predators. Penguin diet Themisto gaudichaudii. Target discrimination-Southern Ocean O Inter-Research 1996 Resale of full article not permitted

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“…Binary data were converted to a format compatible with the data-visualisation software AVS (Upson et al 1989). In this environment erroneous data points, due for example to bottom integration, false bottom echoes or surface noise, \Irere removed (Socha et al 1996), and tlme varied gain (TVG) amplifi.ed background noise was subtracted. using an algorithm described by Watkins & Brierley (1996).…”

Section: Introductionmentioning

confidence: 99%

Interannual variability in krill abundance at South Georgia

Brierley¹,

Watkins²,

Murray³

1997

Mar. Ecol. Prog. Ser.

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Interannual variability within the pelagic marine environment around South Georgia is a well-recognised phenomenon. A key aspect of this variability is interannual fluctuation in the abundance of Antarctic krill Euphausia superba. Here we describe a new acoustic survey programme to monitor krill abundance in the South Georgia region. We present biomass estimates for 2 survey boxes, located over the shelf-break to the northeast and northwest of the island, derived from the first of these surveys conducted in January 1996. We contrast these with the most recent previous estimates for the region obtained in January 1994. Weighted mean krill density (and weighted variances) estimates for the 1996 surveys were 40.57 g m-' (13.37) and 26.48 g m (54.30) for the eastern and western boxes respectively. These are high compared with those obtained in January 1994, when estimates for similar areas were 1.87 g m-? (0.14) and 7.43 g m-2 (1.33) respectively. The greater than 20-fold difference between surveys reveals a very large interannual variability in krill abundance at South Georgia. In 1994 the low abundance resulted in greatly reduced breeding success in most habitual knll predator species there. In the 1996 season, however, breeding success of these species was normal. Instantaneous estimates of knll abundance uslng acoustic techniques are therefore consistent with measurements from predators, whose b r e e d~n g performances provide a longer-term indication of prey abundance in the surrounding pelagic ecosystem in a particular season

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A visualization-based post-processing system for analysis of acoustic data

Cited by 14 publications

References 8 publications

An operational system for processing and visualizing multi-frequency acoustic data

An operational system for processing and visualizing multi-frequency acoustic data

Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity

Interannual variability in krill abundance at South Georgia

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