Mapping and Hydrographic Surveys (MHS) is an Australian company offering professional hydrographic and geophysical survey services to the coastal engineering, port development and maintenance, and offshore oil and gas industries.
MHS has gained extensive experience in all marine environments, from the open ocean to harbours, dams and creeks. MHS specialises in remote locations and has the technological knowledge and equipment to accurately identify the seabed for greenfield port investigations, engineering design, dredging surveys and under keel clearance surveys.
MHS can offer several marine seismic and sub bottom profiling systems such as high-resolution BOOMER and PINGER systems, CHIRP systems and bottom-towed marine refraction systems, all of which are well-known and well-accepted marine geophysical systems.
MHS has become aware of the growing trend for port development and marine infrastructure engineering to require broader and deeper geophysical investigations, and that current 'sub bottom profiling' geophysical techniques are falling short of these requirements.
Mapping and Hydrographic Surveys, together with a consultant from the US, has developed a high-resolution 2D marine reflection seismic system to meet the needs of port development and marine infrastructure engineers.
Based on the well-proven offshore oil industry 2D seismic system, MHS's high-resolution 2D marine reflection seismic system has been designed specifically to acquire high-definition 2D reflection seismic and compressional P-wave velocity data over a target penetration depth of 50m. MHS has been operating the system on current projects with considerable success.
MHS's MKII 2D marine seismic tomography system uses a specialised seismic sound source and a highly sensitive 24-channel hydrophone array streamer with matched frequency response ranging from 10Hz to 2.5kHz. This system can now acquire both depth of penetration to 50m through harder seabed materials with velocities exceeding 2,700m/s, define the nearer (softer) sub seabed strata reflectors, and provide compressional P-wave velocities throughout the vertical profile.
MHS now offers new 2D marine seismic tomography capability to ports, harbours and the maritime engineering community.
MHS's MKIII 2D marine reflection seismic system is an easily portable system configured with a 12-channel hydrophone array streamer. Using a lower energy seismic source, it is designed to achieve higher resolution of the upper seabed strata to 20m penetration specifically for maritime engineering and dredging investigations. This system should not require an EPBC referral (for the non disturbance of marine creatures) to allow its operation in Australian waters.
Analysis and processing of the seismic data is carried out using automated computer-based systems, resulting in a much faster turnaround than using traditional manual methods of processing and analysis of seismic and sub seabed data.
MHS operates Kongsberg EM 3000 multi-beam echo sounding systems installed in the company's dedicated survey vessels and Odom ES3-M multi-beam echo sounding systems as portable systems to install in vessels of opportunity.
MHS also operates Atlas DESO 300 and Raytheon DE 719 single-beam echo sounders using the selectable 200kHz frequency.
All MHS echo sounders have a resolution of 0.01m and accuracy of +0.05m and are interfaced to a motion reference unit (for heave) and GPS compass unit (for heading). Digital data is recorded by an interfaced computer at the rate of ten soundings per second, which is also displayed on analogue trace.
MHS operates real-time differential dual-frequency GPS (NavComV, StarFire) using International Terrestrial Reference Frame (ITRF) differential corrections transmitted from the reference stations received via the onboard Inmarsat satellite data link. Accuracy of horizontal positioning is +0.1m.
MHS operates the PC-based dedicated survey package QINSy, which is interfaced with a positioning system and sensors, and provides pre-survey design, online navigation control, data logging of full raw data set and real-time quality control onscreen information.
MHS's C-Max CM2 digital side scan sonar is a dual-frequency, high-resolution side scan sonar system, with image correction and automatic range adaptive gain control, suitable for use in small vessels.
The system uses linear transducer arrays mounted on an underwater towfish, to transmit two acoustic beams at right angles to the towfish, one to port and one to starboard. The beams are narrow width (along track coverage), normally 1°, and wide in the vertical coverage, normally 32° at 100kHz.
The low 325kHz frequency is attenuated less by the passage through seawater and therefore gives maximum range to 150m either side.
The high 780kHz frequency is more useful at shorter ranges (less than 50m either side) by providing higher resolution and therefore better images of small seabed objects. Side scan imagery is recorded directly to the QINSy navigation package, and is processed and presented in real-time as a mosaic in the multi-layered QINSy navigation display.