{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,25]],"date-time":"2026-02-25T18:18:50Z","timestamp":1772043530471,"version":"3.50.1"},"reference-count":30,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2018,6,6]],"date-time":"2018-06-06T00:00:00Z","timestamp":1528243200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Aristeia-II Program (European Union Social Fund \u2013 ESF, and Greece through NSRF 2007-13, Operational Program &quot;Education and Lifelong Learning&quot;)","award":["3495\/2014-15"],"award-info":[{"award-number":["3495\/2014-15"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>A series of underwater acoustic localization experiments were conducted in the Eastern Mediterranean Sea to test the performance of a Bayesian method for localization of pulsed acoustic sources exploiting time differences between direct and surface-reflected arrivals at two hydrophones of known depth. The experiments involved a controlled source (pinger) at various depths\/ranges as well as vocalizing sperm whales encountered off southern Crete. The localization method provides primarily range and depth information. In addition, if the location of the hydrophones in the horizontal is known, horizontal localization can be performed as well, subject to left\u2013right ambiguity; this was applied for whale localization. The localization results confirmed the anticipated behavior of range, depth, and bearing estimation errors, which, according to theory, depend mainly on the source azimuth. In particular, range and depth estimation errors are larger for source locations close to broadside to the array and smaller towards endfire, and they increase with range. Conversely, bearing estimation errors are larger close to endfire and smaller towards broadside. Localizations in this paper were performed to ranges of about 3.5 km. The limiting factors for localization to longer ranges were the loss of ability to resolve direct and surface-reflected arrivals as well as the self-noise of the hydrophones.<\/jats:p>","DOI":"10.3390\/rs10060883","type":"journal-article","created":{"date-parts":[[2018,6,6]],"date-time":"2018-06-06T07:38:15Z","timestamp":1528270695000},"page":"883","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Underwater Acoustic Pulsed Source Localization with a Pair of Hydrophones"],"prefix":"10.3390","volume":"10","author":[{"given":"Emmanuel","family":"Skarsoulis","sequence":"first","affiliation":[{"name":"Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Crete, GR 70013 Heraklion, Greece"}]},{"given":"George","family":"Piperakis","sequence":"additional","affiliation":[{"name":"Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Crete, GR 70013 Heraklion, Greece"}]},{"given":"Michael","family":"Kalogerakis","sequence":"additional","affiliation":[{"name":"Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Crete, GR 70013 Heraklion, Greece"},{"name":"Technological Education Institute-Crete, Crete, GR 71410 Heraklion, Greece"}]},{"given":"Emmanuel","family":"Orfanakis","sequence":"additional","affiliation":[{"name":"Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Crete, GR 70013 Heraklion, Greece"}]},{"given":"Panagiotis","family":"Papadakis","sequence":"additional","affiliation":[{"name":"Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Crete, GR 70013 Heraklion, Greece"}]},{"given":"Stan.","family":"Dosso","sequence":"additional","affiliation":[{"name":"School of Earth and Ocean Sciences, University of Victoria, Victoria, CA V8W 2Y2, USA"}]},{"given":"Alexandros","family":"Frantzis","sequence":"additional","affiliation":[{"name":"Pelagos Cetacean Research Institute, Terpsichoris 21, 16671 Vouliagmeni, Greece"}]}],"member":"1968","published-online":{"date-parts":[[2018,6,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"714","DOI":"10.1177\/0278364908100561","article-title":"Cooperative localization for autonomous underwater vehicles","volume":"28","author":"Bahr","year":"2009","journal-title":"Int. J. Robot. Res."},{"key":"ref_2","first-page":"549","article-title":"The development of practical techniques for surveying sperm whale populations acoustically","volume":"42","author":"Leaper","year":"1992","journal-title":"Rep. Int. Whal. Comm."},{"key":"ref_3","unstructured":"Kelland, N.C. (2018, March 12). Deep-Water Black Box Retrieval. Available online: http:\/\/www.hydro-international.com\/issues\/articles\/id1130-Deepwater_Black_Box_Retrieval.html."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Brekhovskikh, L., and Lysanov, Y. (1982). Fundamentals of Ocean Acoustics, Springer.","DOI":"10.1007\/978-3-662-02342-6"},{"key":"ref_5","first-page":"691","article-title":"Sound source location by arrival times on a non-rigid three-dimensional hydrophone array","volume":"19","author":"Watkins","year":"1972","journal-title":"Deep-Sea Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"247","DOI":"10.47536\/jcrm.v5i3.804","article-title":"Sperm whale distribution and seasonal density in the Faroe Shetland Channel","volume":"5","author":"Hastie","year":"2003","journal-title":"J. Cetacean Res. Manag."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1121\/1.3598454","article-title":"An algorithm for the localization of multiple interfering sperm whales using multi-sensor time difference of arrival","volume":"130","author":"Baggenstoss","year":"2011","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"446","DOI":"10.1111\/j.1748-7692.2005.tb01243.x","article-title":"Patterns of sound production in diving sperm whales in the Northwestern Mediterranean","volume":"21","author":"Teloni","year":"2005","journal-title":"Mar. Mamm. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3352","DOI":"10.1121\/1.4874601","article-title":"Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles","volume":"135","author":"Tran","year":"2014","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"805","DOI":"10.1121\/1.408391","article-title":"A time-domain backpropagating ray technique for source localization","volume":"95","author":"Voltz","year":"1994","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1582","DOI":"10.1121\/1.1289409","article-title":"Source ranging with minimal environmental information using a virtual receiver and waveguide invariant theory","volume":"108","author":"Thode","year":"2000","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1121\/1.3257211","article-title":"Broadband source localization using horizontal-beam acoustic intensity striations","volume":"127","author":"Turgut","year":"2010","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"336","DOI":"10.1121\/1.2139074","article-title":"The array invariant","volume":"119","author":"Lee","year":"2006","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1121\/1.4973812","article-title":"Array invariant-based source localization in shallow water using a sparse vertical array","volume":"183","author":"Song","year":"2017","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_15","unstructured":"Skarsoulis, E.K., Frantzis, A., and Kalogerakis, M. (2004, January 5\u20138). Passive localization of pulsed sound sources with a 2-hydrophone array. Proceedings of the 7th European Conference on Underwater Acoustics, Delft, The Netherlands."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"245","DOI":"10.1121\/1.1758972","article-title":"Tracking sperm whale (Physeter macrocephalus) dive profiles using a towed passive acoustic array","volume":"116","author":"Thode","year":"2004","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2934","DOI":"10.1121\/1.2041267","article-title":"Ray-theoretic localization of an impulsive source in a stratified ocean using two hydrophones","volume":"118","author":"Skarsoulis","year":"2005","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1202","DOI":"10.1016\/j.apacoust.2006.05.009","article-title":"Two-hydrophone localization of a click source in the presence of refraction","volume":"67","author":"Skarsoulis","year":"2006","journal-title":"Appl. Acoust."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3575","DOI":"10.1121\/1.2049068","article-title":"Three-dimensional passive acoustic tracking of sperm whales (Physeter macrocephalus) in ray-refracting environments","volume":"118","author":"Thode","year":"2005","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2221","DOI":"10.1121\/1.4930937","article-title":"Linearized two-hydrophone localization of a pulsed acoustic source in the presence of refraction: Theory and simulations","volume":"138","author":"Skarsoulis","year":"2015","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_21","unstructured":"Tarantola, A. (1987). Inverse Problem Theory, Elsevier."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1002\/aqc.2435","article-title":"Sperm whale occurrence, site fidelity and population structure along the Hellenic Trench (Greece, Mediterranean Sea)","volume":"24","author":"Frantzis","year":"2014","journal-title":"Aquat. Conserv. Mar. Freshw. Ecosyst."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1129","DOI":"10.1121\/1.381646","article-title":"Speed of sound in seawater at high pressures","volume":"62","author":"Chen","year":"1977","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_24","unstructured":"Jensen, F.B., Kuperman, W.A., Porter, M.B., and Schmidt, H. (2000). Computational Ocean Acoustics, Springer."},{"key":"ref_25","unstructured":"Burdic, W.S. (1984). Underwater Acoustic System Analysis, Prentice-Hall."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"575","DOI":"10.1109\/TIT.1984.1056901","article-title":"On the Cramer-Rao bound for time delay and Doppler estimation","volume":"30","author":"Friedlander","year":"2003","journal-title":"IEEE Trans. Inf. Theory"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1088\/0959-7174\/13\/4\/301","article-title":"Travel-time statistics for signals scattered at a rough surface","volume":"13","author":"Godin","year":"2003","journal-title":"Waves Random Media"},{"key":"ref_28","unstructured":"Massel, S.R. (1989). Hydrodynamics of Coastal Zones, Elsevier."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1279","DOI":"10.1121\/1.413465","article-title":"Time and frequency-domain characteristics of sperm whale clicks","volume":"98","author":"Goold","year":"1995","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2254","DOI":"10.1121\/1.1360718","article-title":"Vocal behavior of male sperm whales: Why do they click?","volume":"109","author":"Jaquet","year":"2001","journal-title":"J. Acoust. Soc. Am."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/6\/883\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:07:31Z","timestamp":1760195251000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/6\/883"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,6,6]]},"references-count":30,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2018,6]]}},"alternative-id":["rs10060883"],"URL":"https:\/\/doi.org\/10.3390\/rs10060883","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,6,6]]}}}