This highly advanced system allows precisely repeatable seabed feature mapping in a robust and reliable package. The system utilises high resolution direct digital sampling of the received signals, and full digital processing. This new technology offers unprecedented resolution and dynamic range (24 bit), simultaneous dual frequency operation (114/410 kHz), digital lters, pulse width auto adjust to optimise for any sample rate setting and a new high speed digital data link enabling very long lengths of low drag co-axial tow cable to be used. The system conguration, low power and small size make the DSSS ideally suited for installation onto a Remotely Operated Vehicle (ROV), or an Autonomous Underwater Vehicle (AUV) as well as combined proler/magnetometer tow sh.
Deck Unit – GeoAcoustics Universal Transceiver
The GeoAcoustics Universal Transceiver contains power supplies and all connections and interfaces to power the tow sh down the tow cable; to facilitate bidirectional communication for control and status reporting: and to transfer data from the tow sh. The ultra high dynamic range means that no user controls are necessary to acquire raw digital data of the highest possible quality. Side scan images can be processed in real time from this raw data using the DSSS-Viewer software package provided with the system. The Deck Unit includes GPS interfaces and automatically synchronises the tow sh to GPS time using the 1PPS signal. This ensures accurate absolute time stamping for all data. The system also has real time triggering capability to allow the use of responders for accurate tow sh positioning relative to the vessel. The digital sonar data is also streamed out on Ethernet for use in real time by a digital acquisition system such as GeoPro-DSSS.
The sub-sea electronics of the Digital Side Scan Sonar system can be mounted in a tow sh, on a combined tow sh or on an AUV or ROV. The use of standard sub-sea connectors and standard protocol interfaces allows easy installation in all situations. The sub sea electronics unit includes all sonar transmitter and receiver electronics as well as digital signal processing, attitude sensor, magnetometer interface, and tow cable data transmission. This ensures lossless sonar data transfer and highly repeatable sonar performance regardless of cable length.
The robust high speed (8 Mbits/sec) data transfer system, high raw data resolution (24 bits) and high output data rate (50 kHz) eliminates any bandwidth/ resolution trade-offs inherent in other digital sonar systems.
The standard system employs a stainless steel tow sh and can operate to a depth of 1000 metres. The basic system includes the following:
• Deck Unit – GeoAcoustics Universal Transceiver complete with DSSS-Viewer software.
• Digital Side Scan Tow sh, which houses the Subsea Electronics and Two Dual Frequency Transducers (Port and Starboard). Options include enhanced software and interfaces to additional hardware, tow cables and deck cables.
• 1000 metre depth rating (standard).
• Simultaneous dual frequency operation.
• 24 bit dynamic range/resolution.
• Robust digital data transmission over long cables.
• Attitude sensor.
• High efciency/low power for AUV/ROV.
• Low drag coaxial tow cable.
• Very high system bandwidth and resolution.