Date ( Creation )

2018-05-01

Identifier

http://data.bgs.ac.uk/id/dataHolding/13607327

Maintenance and update frequency

notApplicable notApplicable

GEMET - INSPIRE themes

• Geology

BGS Thesaurus of Geosciences

• Seismic data , Rivers , Bathymetry , Sedimentary geology

Keywords

• NERC_DDC

Access constraints

otherRestrictions Other restrictions

Use constraints

otherRestrictions Other restrictions

Other constraints

The copyright of materials derived from the British Geological Survey's work is vested in the Natural Environment Research Council [NERC]. No part of this work may be reproduced or transmitted in any form or by any means, or stored in a retrieval system of any nature, without the prior permission of the copyright holder, via the BGS Intellectual Property Rights Manager. Use by customers of information provided by the BGS, is at the customer's own risk. In view of the disparate sources of information at BGS's disposal, including such material donated to BGS, that BGS accepts in good faith as being accurate, the Natural Environment Research Council (NERC) gives no warranty, expressed or implied, as to the quality or accuracy of the information supplied, or to the information's suitability for any use. NERC/BGS accepts no liability whatever in respect of loss, damage, injury or other occurence however caused.

Other constraints

Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced NERC materials "Contains NERC materials ©NERC [year]"

Metadata language

English English

Topic category

• Geoscientific information

Geographic identifier

BANGLADESH [id=498000]

 

Date ( Creation )

1979

Geographic identifier

BD

 

Date ( Revision )

2009

Geographic identifier

BGD

 

Date ( Revision )

2009

N

S

E

W

Distribution format

• TXT files ()

• SEGY files ()

OnLine resource

http://www.bgs.ac.uk/services/ngdc/accessions/index.html#item110050  

OnLine resource

http://www.bgs.ac.uk/services/ngdc/citedData/catalogue/21394db3-89db-4dd3-bec7-f25913edc919.html  

Hierarchy level

dataset Dataset

Other

dataset

Statement

Boomer Sub-Bottom Profiler Seismic reflection profiles were acquired using the University of Southampton’s Boomer sub-bottom profiler. Consisting of an Applied Acoustics AA200 plate mounted on a small, lightweight catamaran, the system is powered by an Applied Acoustics CSP300 Capacitor Discharge box capable of duty cycles up to 2 PPS at a maximum power output of 300 J. The Boomer provides a highly repeatable, broad bandwidth, impulsive seismic source with frequencies ranging between 0.4 kHz and 4.0 kHz, peaking at c. 1.5 kHz. During surveying, the catamaran was towed c. 15 m astern of the MV Kokilmoni, immediately behind the launch boat (see Fig. 1a). Use of the launch made for easier deployment/retrieval (lower sided than MV Kokilmoni), and acted to shield the catamaran from propeller wash during surveying. Data was recorded using an 11-element mini-streamer (c. 3 m long active section) towed off a 0.5 m long boom on the port stern quarter. Lateral offset between source and receiver was c. 5 m, while the inline offset was varied during the early part of the survey to optimize imaging (settling on c. 20 m behind the vessel from 16/06/2013). Raw analogue data was digitized using a CODA Octopus DA2000, and stored to disk as unprocessed SEG-Y files with navigation from the catamaran mounted GPS antenna. Chirp Sub-Bottom Profiler To complement the lower-frequency, higher-penetration Boomer profiles, seismic reflection data were also acquired using the University of Southampton’s higher-frequency, lower-penetration Chirp sub-bottom profiler. Consisting of a modified GeoAcoustics digital GeoPulse and 7-element mini-streamer (1.0 m long active section), this system produces a swept-frequency (1.5 – 13.0 kHz), tunable, highly repeatable (99.9%) source waveform 32.74 ms in length. Data was recorded using a CODA Octopus acquisition system (version 5.4) as unprocessed SEG-Y files. During acquisition, the Chirp catamaran was towed in a similar manner to the Boomer catamaran (see, Fig. 1b); c. 5 m astern of the launch boat, c. 20 m astern of the MV Kokilmoni. The streamer was towed directly behind the catamaran, using an extension cable to provide source-receiver offsets of order 5 m. With the difficulty of deploying the heavy Chirp catamaran without a winch/A-frame, it was felt the risk of mounting the GPS antenna directly on the catamaran was too great. Therefore, positioning for Chirp data is relative to the GPS antenna mounted on the launch boat and therefore requires layback correction (c. 10 m). Multi-Beam Bathymetry Multi-beam bathymetry was acquired using a Reson SeaBat 8125 High-Resolution Focused Multi-Beam Echosounder. Operating at 455 kHz, the 8125 transducer emits 240 individual beams that are 0.5° x 1.0° in size at the nadir and 1.0° x 1.0° in size at the outer beams. The 8125 utilizes high-frequency beam forming to produce excellent near field imagery, and is therefore especially well suited to shallow water depths; maximum of 120 m and optimum imaging at 60 m and less. The sonar head was mounted on a specifically designed and constructed over-the-side pole, mounted on the forward starboard quarter of the vessel. The 6 m-long pole positioned the head just beneath the maximum keel depth of the vessel (c. 2.0 m below the water line). Positional information was provided by-way of two GPS antennae mounted on the bridge roof (supplied with DGPS correction strings via Omnistar subscription) and a PosMV Inertial Motion Reference Unit (IMU) located in the dining room. The location of each component was measured in prior to the start of the survey, using the PosMV as the 0,0,0 reference location.

gmd:MD_Metadata

File identifier

6d03a207-09e5-2c27-e054-002128a47908   XML

Metadata language

English English

Hierarchy level

dataset Dataset

Date stamp

2021-07-30

Metadata standard version

2.3

Dataset URI

http://data.bgs.ac.uk/id/dataHolding/13607327