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ACOUSTIC POSITIONING SYSTEMGroup members:Mohammad Fazrul Shafiq Bin AliasMuhamad Syazwan Syah Bin AdnanMohamad Hafizuddin Bin RakabayMuhamad Aminuddin Bin M.YusoffMuhamad Hilman Bin HisamudinFatin Najwa Binti Md JaisNur Fatin Amiera Binti RazaliNoor Shafiqah Binti SamsuriSiti Ramizah Binti Ismail

INTRODUCTIONRadio signals used by surface positioning systems are absorbed by water, as a result acoustic signals are the preferred technology for in water signalling.Acoustic method usually used for positioning at offshore and deep water sea. This positioning method calculate distance by recording transmitted and received back pulse. The main factor in this method is the accuracy of sound velocity in the water column. The acoustic positioning system not measure distance but it measure the time.Example of Acoustic positioning system in field work:Tow fish trackingBundle TowsCivil EngineeringVessel and Drill Platform

WHAT IS ACOUSTICS USED FOR?Transfer of position from surface to seabed (most oil industry work relates to drilling and installations on the seabed)Positioning within the water column (Survey Sensors)Relative positioning between locations (relative installations, metrology)Transmission of data (to support positioning and independent sensor data)INSTRUMENTTYPE OF TRANSPONDERSTHREE MAIN METHOD IN ACOUSTIC SHORT BASELINE (SBL)Determines beacon position by measuring the relative arrival times at three or more vessel mounted hydrophones

LONG BASELINE (LBL)Determines beacon position by measuring the slant ranges from three or more widely spaced transponder

UltraShort baseline (USBL)

Determines beacon position by measuring the relative phases of the acoustic signal received by closely spaced elements in a single hydrophone

Ultra short baseline theory of operation:

Acoustic accuracies

BENEFIT OF ACOUSTIC METHODOperating Model

Advantage Disadvantage Short BaselineHighest Potential Accuracy Accuracy preserved over wider operating area

Requires Multiple Subsea Transponders Must have two-way ranging Update intervals long compared to pinger modes Acoustic ray bending

Long BaselineGood Potential Accuracy Requires only a single Subsea Pinger/Transponder

Accuracy dependent on shipboard VRU Ultrashort BaselineRequires only a single Subsea Pinger/Transponder

Highest Noise susceptibilityAccuracy dependent on shipboard VRUCONCLUSIONAcoustic method is simple and high accuracy that require it to conduct the survey at the deep shore.Acoustic method only measure time and it will put in the formula to get the real coordinates.For high accurancy positioning on the seabed a different type of LBL is used.In this methodology more intelligent transponders are used which are individually addressable and commandable.

REFERENCESWikipedia(2013,May 11). Short baseline acoustic positioning. Retrieved February 9,2014, from http://en.m.Wikipedia.org/wiki/short_baseline_acoustic_positioning_systemE.Moller(2012,April 11).Acoustic(Subsea)Positioning System, retrieved February 9,2014 from Hydrofest 2012