Source Range Estimation in the Ocean using Time Difference of Multipath Arrivals

89 Pages·2016·3.46 MB·English

by  Narve Garshol Skurtveit

Source Range Estimation in the Ocean
using Time Difference of Multipath
Arrivals
Narve Garshol Skurtveit
Master of Science in Electronics
Submission date: June 2016
Supervisor: Hefeng Dong, IET
Co-supervisor: Dag Tollefsen, Forsvarets forskningsinstitutt (FFI)
Norwegian University of Science and Technology
Department of Electronics and Telecommunications

Science, my lad, is made up of mistakes, but
they are mistakes which it is useful to make,
because they lead little by little to the truth.
- Jules Verne

Acknowledgements
I wish to thank Dag Tollefen at FFI for always replying to my questions, review
of my work and providing relevant literature. Further, I wish to thank Espen
Rustad for linguistic guidance. I want to thank Julie, my fiancè, for always
supporting me. I would also like to thank Hefeng Dong for valuable discussion
andreviewofmywork. Finally, IwouldliketothankJohnGebbieforanswering
my questions regarding details of his algorithm.
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Abstract
Passive acoustic ranging in the underwater channel is a challenging task. It has
been studied and used in military applications such as passive sonar, but also by
marine biologists for mammal detection and ranging. Effective passive ranging
is challenging due to the complexity of the underwater channel, and the often
changing environmental parameters. Most methods also require a long array to
estimate bearing and distance at long ranges.
In this project a ranging method based on a ray model is studied. The source
range is estimated by comparing differences in signal time arrivals received on
two spatially separated hydrophones. The method is applied to data from two
bottom moored hydrophones from two different data sets in shallow water: one
with the hydrophones moored at 16m depth, the other at 200m. The method
provides stable range estimates of surface ships and small boats up to ranges of
700m, in good correspondence with reference data.
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Samandrag
Passiv akustisk avastandestimering i havet er utfordrande. Det blir forska på og
bruktimilitæresystemsompassivsonar,menogsåavmarinbiologartilavstand-
sestimering av dyr. Passiv avstandsetimering er utfordrande grunna komplek-
sitetenihavetmedstadigendringideiakustiskeparameteranesompåverkarut-
breiingaavlyd. Idetteprosjekteteravstandsestimeringbasertpåeinrettgåande
strålemodellstudert. Avstandenblirestimertvedåsamanliknemåltetidsankom-
star frå direkte lyd og overflate/botnreflekter-lyd med modellerte tidsankomstar
påtohydrofonar. Avstandsestimatasomerpresenterterfråtodatasettmedbot-
nmontertehydrofonar. Ideteinedatasetteterhydrofonanepå16metersdjupog
pådetandredatasettetpå200metersdjup. Metodengirstabileavstandsestimat
ut til 700 m og korresponderar godt med referansedata.
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