NDLI: In-situ far-field calibration of multibeam sonar arrays for precise backscatter imagery

Content Provider	IEEE Xplore Digital Library
Author	Fusillo, L. de Moustier, C. Satriano, J.H. Zietz, S.
Copyright Year	1996
Description	Author affiliation: Computer Sci. Corp., Moorestown, NJ, USA (Fusillo, L.)
Abstract	Calibration of large hull-mounted sonar transducer arrays is usually done by measuring the performance of individual components in a test tank. Multiple transducer element beam patterns are superimposed and combined with window attenuation and other partial measurements to give an approximation of the total beam pattern. This process often ignores or fails to accurately model factors such as mounting hardware, array misalignment, reflections from the hull structure and other real world absorbers, reflectors and attenuators which can have significant effect on the actual beam pattern. This paper describes an application of a novel technique for in-situ measurement of the far-field beam pattern of an entire installed hydrophone array using an ROV to carry a calibrated reference transducer. The sonar array is part of a Simrad EM-121 multibeam sonar system installed aboard the Navy's new survey ship the USNS SUMNER TAGS-61. Test tank measurements of individual hydrophone transducer packages were available and a composite array beam pattern was computed from this data. Direct at-sea measurement of the far-field beam pattern was then made by placing a reference transducer on an ROV and navigating it through an are in the far field of the shipboard array. These two sets of beam patterns are compared. Backscattered signals in a multibeam sonar system can be the basis for characterization of seafloor morphology in terms of mud, clay, silt, sand, gravel, rocks, etc. The degree of differentiation between bottom types, or the number of bottom types which can be differentiated, depends on how accurately the signal strength is calibrated. Factors which affect this measurement include the sonar transmitter electrical output, projector efficiency, projector array beam pattern, spreading loss and attenuation in the water column, losses at the bottom reflection, hydrophone array beam pattern, hydrophone sensitivity and receiver gains. The degree of improvement in seafloor characterization resulting from the in-situ hydrophone array calibration are examined.
Starting Page	47
Ending Page	49
File Size	313532
Page Count	3
File Format	PDF
ISBN	0780335198
DOI	10.1109/OCEANS.1996.566716
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1996-09-23
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Calibration Sonar measurements Transducers Sonar equipment Testing Attenuation measurement Optical reflection Remotely operated vehicles Sonar navigation Sea floor
Content Type	Text
Resource Type	Article

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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