Small and easy-to-use, the acoustic doppler Aquadopp current profiler has become a favorite for use in estuaries and shallow coastal water. With the introduction of the new “mid-life” electronics in 2008, it has become shorter by 10 cm, the profiling range has increased, the power consumption has come down even further and is the staple for water current measurement.
When the acoustic doppler Aquadopp Profiler was introduced in 2000 it represented a completely new generation of current profilers, and even today it remains a cutting edge current profiler. At 2.4 kg, you can carry 2 under each arm, you can deploy it with ease, and you can mount it in places you never dreamed of. The Aquadopp Profiler provides high quality accurate and unbiased data, and it has the classical advantages of acoustic Doppler systems including insensitivity to biofouling and no moving or protruding parts.
The Aquadopp Profiler is an inexpensive tool for shallow water measurements on time scales larger than 1 second. It gives you speed and direction in up to 128 different layers of the water column. The system electronics integrates Doppler velocity with temperature, pressure, tilt, and compass information – all standard with each instrument. The system also has built-in solid state recorder and batteries. State-of-the-art power management and miniaturized electronics combine in a compact single-canister design that is suitable for real-time operation or self-contained deployments.
The Aquadopp Current Profiler comes with a complete suite of Windows® 2000/XP/Vista software for deployment planning, real time data collection and data retrieval. For special applications, the system can be operated from any third party controller using the RS232 or RS422 interface or your own PC program using Nortek ActiveX controls.
In the summer of 2008, the Aquadopp profiler was equipped with the midlife electronics. This board is 10 cm shorter so the standard length of the instrument (batteries included) shrunk to a little more than 40 cm. Other improvements:
Range increased by 20-30% due to increased output power
Maximum solidstate recorder increased to 9/32/176/352 MB
Canister length can be increased to accomodate double alkaline batteries so deployment lengths can be doubled. Two lithium batteries is only an option.
The Aquadopp Profiler is designed with flexibility in mind. Typical applications include shallow water oceanography (< 100 m water depth), harbor monitoring, and scientific studies in rivers, lakes, and channels. It can be deployed in small, low cost bottom frames, on a mooring rig, on a moored surface buoy or on any other fixed structure. The Aquadopp Profiler works equally well in typical ocean surface water and in the high sediment suspensions found near the coast or in rivers. A variety of head designs ensure optimal measurement conditions regardless of deployment surroundings. The Aquadopp Profiler can be used in stand-alone mode with internal data recording or online, communicating via phone or radio modem.
The Aquadopp profiler can also collect wave data measurements (PUV) interleaved with the mean current profiles and can thus be operated as a combined wave and current system if there is adequate recorder space and battery capacity.
Nortek shipped the first Aquadopp Profilers in the summer of 2000 and today it is used by scientists and engineers at well-known oceanographic institutions in all corners of the world, for shallow water measurements and oceanographic research. Please contact Nortek or your local representative for a detailed customer reference list.
Download brochure: Aquadopp Profiler
Current profiles and wave height & direction data with a single instrument!
With the Nortek AWAC, you get a current profiler and a wave directional system in one unit. You can measure the current speed and direction in 1-meter thick layers from the bottom to the surface. Waves of all varieties are measureable; this includes long waves, storm waves, short wind waves, or transient waves generated by local ship traffic.
The AWAC is designed as a coastal monitoring system. It is small, rugged, and suitable for multi-year operation in tough environments. The mechanical design is all plastic and titanium to avoid corrosion. The AWAC is available in three transmit frequencies (1 MHz / 600 kHz /400 kHz) which allow for different deployment depths.
The sensor is usually mounted in a frame on the bottom, where it is protected from complications at the surface such as harsh weather, vandalism, and ship traffic. While safely located at the bottom it is operated in online or in stand-alone mode.
In stand-alone mode, the raw data are stored to the internal data logger and power comes from an external battery pack. A variety of options are available with maximum deployment lengths of 10 months with hourly wave data when using lithium batteries.
Online systems have a variety of possible communication configurations. The most common are long, offshore cables (max. 5 km) or acoustic modems. Online systems can be delivered with backup batteries, protected cables, shore side interface units, and online software.
The AWAC’s extraordinary wave performance has largely to do with the optional Acoustic Surface Tracking (AST). The AST is basically echo-ranging to the surface with the vertically oriented transducer. The beauty of this method of measuring waves is that it circumvents the depth limits imposed by bottom mounted pressure and velocity measurements. Long waves (swell) and storm waves are rarely difficult to measure, however waves generated by local winds are challenging without AST. Moreover, the AST also gives you the ability to derive wave parameters based on times series analyses. This means that the AWAC can directly measure wave parameters such as Hmax, H1/10, Tmean, etc. which other bottom mounted systems simply cannot.
The surface is a strong acoustic reflector and this is true also when the water surface is covered with ice. As a result, the AWAC can be used to detect the interface between water and ice. When compared with a reference measurements (either the pressure sensor or mean measurements during periods of open water), the AWAC can be used to estimate the surface ice thickness. This method was used already the winter 2008/2009 in the Arcticwith very good results
Tidal elevation with improved pressure sensor
From the spring of 2011, an improved pressure sensor with an absolute accuracy of 0.1% of full scale is available for the AWAC. For a deployment depth of 20 m (and a 50m full scale sensor), this means the absolute accuracy of the sensor is 5 cm, which is within the requirements for many operational harbor systems
The AWAC software is used to configure the instrument for deployment, retrieve the data and convert all raw data files to ASCII. In order to calculate the wave parameters, you have the choice between the non-graphical QuickWave software and the graphical Stormsoftware. For online systems which require data managements and generating content for internet use (e.g. processed results and graphical plots), the SeaState software serves as the link for all your AWAC wave and current data. For a more detailed description please check out SeaState.
Download Brochure: AWAC_web
A large and consistently growing installed base of equipment within the worldwide seismic fleet distinguishes our company as a dominant supplier in the vessel mounted current profiling business.
Being responsive to new product/application requirements as well as continuously focusing on optimising support and service processes have been key challenges and success factors in this exciting, demanding and rapidly moving business.
How does it work?
What a current meter mounted underneath the vessel hull will measure is basically the vessel speed through water, i.e. a high precision speed log. However, what the navigation crew typically is interested in is the net ocean current speed and direction relative to ground. This is obtained by connecting the vessel gyro and DGPS and subtract the vessel speed over ground from the speed through water value.
What are the benefits of installing a current meter on a seismic survey vessel? There are four major concerns making a current meter a vital part of the navigators positioning setup.
- Feather angles. Currents crossing the vessel track will cause streamer – and geophone – deflection . Knowing and predicting this angle improves the positioning precision and the ability to determine the actual point of data acquisition.
- In-fills. Turning a seismic rig around takes hours, and the operational cost for a seismic vessel is considerable. Thus the ability to plan ahead, reducing the number of “extra” runs is crucial.
- Knowledge about local currents improves the ability to avoid costly entanglements during streamer deployment, handling and recovery.
- Close passes. Today so called 4D runs are becoming increasingly more in demand. This basically means doing new surveys on existing reservoirs in order to determine changes and remaining volumes. These reservoirs usually have existing installations, and predicting streamer path is vital in order to avoid collisions. Streamers can be repositioned vertically in the water column into a layer with more favorable currents.
- HardwareThe basic hardware product offered to the seismic business today is the bronze housing VM AWAC current profiler, developed from the well proven AWAC hardware platform.The system is delivered with a marine certified computer, a power/communication interface unit and cables at customized lengths.
The user interface software being shipped with the system is the SurveyVM, which has been virtually unchanged for a decade, ever since the introduction of the VM current profilerconcept. The basic SurveyVM software has a broad reputation for being an intuitive and easy-to-use product providing useful information even to personnel without basic training or previous introduction.
The ExploreP software package, designed for post processing, analysis and quality control also comes standard with the system.
Current data is becoming increasingly important both in terms of navigational issues and as key oceanographic information made available to the market in a broader perspective.
Keeping pace with this rapidly changing business is encouraging and a continuous challenge in terms of both transducer hardware technology and concept development.
At Nortek we appreciate the fact that working in this professional, competitive and demanding environment has its rewards – it helps us improve – ensuring innovative and reliable solutions also for the future.
Download brochure: VM_profiler
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