Waterfall notch-filtering for restoration of acoustic backscatter records from Admiralty Bay, Antarctica
A series of multibeam sonar surveys were conducted from 2009 to 2013 around Admiralty Bay, Shetland Islands, Antarctica. These surveys provided a detailed bathymetric model that helped understand and characterize the bottom geology of this remote area. Unfortunately, the acoustic backscatter records registered during these bathymetric surveys were heavily contaminated with noise and motion artifacts. These artifacts persisted in the backscatter records despite the fact that the proper acquisition geometry and the necessary offsets and delays were applied during the survey and in post-processing. These noisy backscatter records were very difficult to interpret and to correlate with gravity-core samples acquired in the same area. In order to address this issue, a directional notch-filter was applied to the backscatter waterfall in the along-track direction. The proposed filter provided better estimates for the backscatter strength of each sample by considerably reducing residual motion artifacts. The restoration of individual samples was possible since the waterfall frame of reference preserves the acquisition geometry. Then, a remote seafloor characterization procedure based on an acoustic model inversion was applied to the restored backscatter samples, generating remote estimates of acoustic impedance. These remote estimates were compared to Multi Sensor Core Logger measurements of acoustic impedance obtained from gravity core samples. The remote estimates and the Core Logger measurements of acoustic impedance were comparable when the shallow seafloor was homogeneous. The proposed waterfall notch-filtering approach can be applied to any sonar record, provided that we know the system ping-rate and sampling frequency.
KeywordsNotch-filter Multibeam Waterfall Backscatter restoration Seafloor characterization Antarctica
This research was supported by Petrobras/Cenpes under the research project “Processamento de Sinais Sonográficos para a Identificação Direta de Hidrocarbonetos”, SAP: 4600505474, 2014/00634-2. This work was partially funded by the Brazilian National Research Council (CNPq) under Grant 311131/2014-0.
- Conceição FV, Ayres-Neto A (2013) Seabed properties analysis from multibeam backscatter data. In: Proceedings of the 2013 IEEE/OES Acoustics in Underwater Geosciences Symposium (RIO Acoustics), p 1, Rio de Janeiro- RJGoogle Scholar
- Fonseca L, Calder B (2005) Geocoder: an efficient backscatter map constructor. In: Proceedings of the US hydrographic. San Diego, CA; 2005Google Scholar
- Hammerstad E (2000) Backscattering and seabed image reflectivity, EM Technical Note, https://www.km.kongsberg.com/ks/web/nokbg0397.nsf/AllWeb/C2AE0703809C1FA5C1257B580044DD83/$file/EM_technical_note_web_BackscatteringSeabedImageReflectivity.pdf
- Kongsberg Maritime (2012) Kongsberg EM 302 Multibeam echo sounder: Product Description, Document number: 302675, Rev. C, 02.03.2012, http://www.shipserv.com/ShipServ/pages/attachments/54162/EM%20302%20Product%20Description.pdf
- Kongsberg Maritime (2013) MRU 5th generation Motion reference for any need. https://www.km.kongsberg.com/ks/web/nokbg0397.nsf/AllWeb/E86E824F7306F15CC1256FDC003C9BEF/$file/MRU_family.pdf?OpenElement
- Magrani FJG (2014) Caracterização Sedimentar Glaciomarinha da deglaciação da Baía do Almirantado desde o Último Máximo glacial, Arquipélago das Shetland do Sul, Antártica. Mestrado em Geologia e Geofísica Marinha, Universidade Federal Fluminense (UFF), NiteróiGoogle Scholar
- Park BK, Yoon HI, Woo HJ, Lee KS, Barg EJ, Southern J (1995) Late holocene paleoceanography from core sediments in Admiralty Bay and Maxwell Bay, King George Island, Antarctica. J Korean Soc Oceanogr 30(4):302–319Google Scholar
- Pohner F, Fonseca L, Bakke J, Nilsen K, Kjaer T (2007) Integrating imagery from hull mounted sidescan sonars with multibeam bathymetry. In: Hydro 2007, Norfolk, VA. Proceedings Hydro 2007Google Scholar
- QGIS Development Team (2009) QGIS Geographic Information System. Open Source Geospatial Foundation. URL http://qgis.osgeo.org. Accessed 18 December 2016
- Rosa LAS (2007) Seafloor characterization of the historic area remediation site using angular range analysis. Master of Science in Ocean Engineering (ocean mapping), University of New HampshireGoogle Scholar
- Souza-Filho CR, Drury AS, Denniss AM, Carlton RWT, Rothery DA (1996) Restoration of corrupted optical Fuyo-1 (JERS-1) data using frequency domain techniques. Photogramm Eng Remote Sens 62(9):1037–1047Google Scholar