Three Crucial Hydrographic Survey Instruments

Water level recorder equipment for collecting Hydrographic Survey information include options for both shore based and offshore / seabed applications along with telemetry systems for secure data exchange.

The main three essential hydrographic survey devices are listed below.

1. Echosounder

Bathymetry: the science of calculating depth. Regardless of whether you are surveying, dredging or managing underwater operations, exact bathymetric information is critical, be it overall water depth or the position of particular equipment within the water column.

Digital signal processing systems that use fuzzy logic are offered in the marketplace. These echo sounders will choose and lock onto the true echo, while automatic power and gain management means that false echoes are minimised and accurate readings can be made in water depths as little as 30cm. Being a stand alone altimeter, this device is suitable for integration into bathymetry equipment. Combining the technology with integral GPS receiver and on board information logging offers echosounders with the advantages of maximum flexibility and quick deployment time.

Echosounders, both single and multi-beam need to have speed of sound records to effectively generate water depth measurements. If standard, small boat echo sounding is needed with sole or dual frequency transducers and interface of external parameters with GPS reference then a single beam echosounder is ideal.

The MIDAS Surveyor has been formulated to deliver a minimal cost alternative for small scale hydrographic surveys. The device is offered with a 210kHz transducer as standard, and uses sophisticated digital signal processing procedures to ensure high accuracy and dependable bottom tracking. With a built in SBAS enabled DGPS receiver, the MIDAS Surveyor will record position and water depth data for over 30 hours, as well as carrying out on-line correction using external heave and tide data inputs. Alternatives include an added 33kHz transducer, or high accuracy 16 channel DGPS receiver.

2. Sound Velocity Profiler

Speed of sound Profilers are currently on offer on the market that will provide the following qualities

a. Genuine Accuracy of ±0.02m/s (Total Error Budget)

b. Precision (peak to peak noise) of ±0.002m/s

c. Operating range of 1375m/s to 1900m/s (covering all environments from fresh water to the Dead Sea and the Marianas Trench)

d. Data rates up to 60Hz (instrument dependent)

One such profiler is the miniSVP, a new budget version, produced to make the best Sound velocity measurements in the world accessible to everyone. Featuring the unique and acclaimed "time of flight" SV sensor, the miniSVP is offered in either 500m rated acetal or 6000m rated titanium versions. A single C cell and large Flash memory allow hundreds of profiles to be recorded, and the pre-set profiling patterns make it possible for it to be setup and put into service quickly and simply.

3. Water Level Recorder

Tidal gauges provide possibly one of the most fundamental of all marine readings - Precise tidal data. This is vital for Port & Harbour Operations, Dredging, Surveying, equipment deployments, and a variety of other uses.

Features include:-

a. logging of tidal data for historical purposes;

b. ability to provide real time information,

c. transmission of data over a variety of telemetry links,

d. network capabilities,

e. fixed displays or access through web or local intranet,

f. seabed fixing or in-line mooring.

The TideMaster is a little, cost effective Tidal gauge, particularly developed for applications where the end user requires an exact record of water height, but with the added possibility of meteorological data via an ultrasonic wind speed and direction sensor. Appropriate for deployment in fresh or salt water, the TideMaster can be deployed for as much as 1 year, dependant on the sampling rate, with device setup and data retrieval via an optional monitor panel or using the PC application supplied. Additionally, the device can be supplied with radio modules for real time data transmission.

By: Liz Stewart

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Established in 1969, Valeport designs and manufactures hydrographic survey instrumentation for the oceanographic, hydrographic and hydrometric communities, with a worldwide customer base that includes:environmental, defence, oil and gas, renewable energy, construction, dredging and civil engineering sectors. To view a range of hydrographic equipment suitable for hydrographic surveys, look at Valeport at www.valeport.co.uk