Echo sounding is a powerful and widely used technique for remote sensing of the marine environment. In order to enhance the power of the echo sounder, a postprocessing system has been designed and realized in standard software that is essentially machine independent. This has been done by adhering to the following international standards' UNIX operating system, C programming language, X Window Systems, Structured-Query Language (SQL) for communication with a relational database, and Transport Control Protocol/Internet Protocol (TCP/IP). Preprocessed data are transferred from the echo sounder to the postprocessing system by means of a local-area network (LAN), namely Ethernet. Development of the postprocessing system, for analysis of such diverse scatterers as plankton, pelagic, and bottom fish, and the bottom itself, is documented in the following way. The history of echo integration is summarized. User requirements for the new system are listed. Reasons are given for the choice of the particular computing environment, including both hardware, software, and external communications. The system design, consisting of data flow and graphical user interfaces, is described. Implementation of the system is' defined through integration techniques and a discussion of performance issues. Operating procedures and the first field trials of the system are described. Several features characteristic of and perhaps unique to the postprocessing system are, for example: ( 1 ) user definition of arbitrarily shaped integration regions, including non-constant-depth intervals, by means of interactive graphics; (2) preprocessor error correction, e.g., adjustment of the noise threshold or redefinition of the detected bottom; (3) use of several color map techniques in order to extract such information as signal strength and shape; and (4) the scheme of interconnections of graphical user interfaces, database, and data files. This work does not introduce a set of computer instructions. It does describe a design philosophy and method of realization that may have broader applications in acoustics than that ostensibly concerned only with the quantitative estimation of fish abundance.
The design of a new echo integrator system is outlined. The B.E.I. is based on preprocessed data from the new SIMRAD EKSOO scientific acoustic measurement system. Raw data are displayed and interpreted on a graphics workstation by means of a specially designed man-machine interface. Principles guiding the design are that the software be machine-independent and be based on internationally approved standards, e.g., UNIX, C, X-Windows, SQL database, GKS. The realization of this and the first sea trials are described. The potential for future developments is discussed. · RESUME Nous presentons dans les grandes lignes un noveau systeme å echo integre. Le B.E.I. se base sur les donnees pretraitees provenant du nouveau systeme de mesurage acoustique scientifique SIMRAD EKSOO. Les donnees brutes sont affichees et interpretees sur un poste de travail graphique au moyen d'un interface homme-machine specialement concu pour cet usage. Les principes ayant guide cette conception sont que le logiciel doit §tre independant de la machine et se baser sur des normes internationales, telles que UNIX, C, X-WINDOWS, base de donnees SQL, GKS. Nous en decrivons la realisation et les premiers essais en mer. On discutera des developpements futurs potentiels.l
Knudsen, H. P. 2009. Long-term evaluation of scientific-echosounder performance. – ICES Journal of Marine Science, 66: 1335–1340. When scientific acoustic instruments are utilized for quantitative measurements of underwater biological resources, it is extremely important to know their overall performance, and it is imperative to measure their stability over time. Echosounders mounted on research vessels are therefore routinely calibrated several times annually, often immediately before, during, and after important resource-assessment surveys. In recent years, multifrequency systems for acoustic surveys requiring species identification and categorization based on the frequency response of targets have been introduced, further emphasizing the importance of monitoring instrument performance. In the 1970s, hydrophones and steel spheres were used as alternative references for calibrations. Substantial variations of system performance were observed, however, and gradually it was accepted that the use of hydrophones was inappropriate, because their performance varied more than that of the instruments being calibrated. Not until optimized reference targets were introduced in ca. 1980, was it possible to monitor the stability of acoustic-survey equipment with an acceptable degree of confidence. For the first time, the true, long-term stability of transducers, including ageing effects, could be accurately measured. This paper gives examples of calibration time-series for several Norwegian research vessels operating in various regions from Arctic to tropical waters.
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