Bangladesh river bathymetry and seismic surveys (NERC grant NE/I023228/1)

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.

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services