Vessel-mounted Current Profiler
A New Approach to 3D Current Profiles from Moving Vessels
The Nortek vessel mounted profiler is designed for professional vessels that are equipped with modern navigation equipment. It is not designed for river applications or for small coastal vessels used for short surveys.
In order to provide the true ocean currents, all vessel-mounted current profilers must subtract the ship velocity from the measured data. The traditional method relies on "bottom track", a technique where the Doppler profiler measures the velocity of the bottom relative to the ship. The Nortek VM-Profiler primarily relies on connecting to the gyro and the DGPS to obtain the vessel velocity. Advantages of the Nortek solution are:
- The water depth is irrelevant and the system works equally well in shallow and deep water (bottom track does not work if the bottom is deeper than the maximum acoustic range)
- The quality of the bottom acoustic conditions is irrelevant (bottom track fails when the bottom is acoustically indistinct)
- High resolution data close to the surface can be collect in deep water (bottom track requires the use of low frequency acoustics because the pulse must always reach the bottom)
The Nortek SurveyP software calculates and graphically presents the ocean currents on a PC. It displays the corrected data in real time, calibrates the installation, automatically stores raw data to file, and can export the data over a serial port to a variety of formats. The SurveyP software can also integrate, display and record data from third party serial systems such as Gill wind sensors and the Navitracker at the same time as it collects current profiles. The software also has an ASCII export function to prepare the data post processing for post processing with your own software.
The VM-Profiler consists of:
- A rugged transducer assembly made from marine bronze and designed for permanent installation.
- A computer with an intelligent multi-port serial interface card ( Windows NT)
- Powerful Survey software to handle in and out going communication from up to 8 serial devices
Applications
The VM-Profiler is used in applications where current profiles are needed from ships in motion. Examples of typical vessels that have chosen the Nortek Profiler are:
- Professional Survey Vessels
- Marine operations (diving, inspection, dredging)
- Deep water seismic survey vessels
- Hydrological vessels in rivers with high sediment concentration.
- Ships of opportunity - ferries
- Fishing vessels
Key Specifications
Detailed specifications are provided in the PDF brochure.
System:
- Acoustic frequencies: 500 kHz, 1.5 MHz
Velocity:
- Velocity range: ±10 m/s
- Accuracy: 1% of measured value ±0.5 cm/s
- Maximum profiling range: 100/20 m for 500kHz/1.5 MHz
- Cell size: 0.4 to 12 m
- Minimum blanking distance: 1/0.4 m
Interfaces:
- GPS receiver: Any receiver with serial output. The accuracy of the GPS velocity should be 0.05 m/s or better (DGPS)
- Gyro: Any gyro with serial output and accuracy better than 1°. It is also possible to use combined gyro and GPS system such as the Seatex Seapath
- Computer: The survey computer needs at least 3 serial ports and it is advisable to use an intelligent multi-port card. Preferred operating system is Windows NT
Mechanical:
- Transducer Material: bronze
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