Sea Wave and Surface Current Monitoring by Marine X Band Radar

by OldSailor on January 2, 2008

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We all know that almost 98% of global trade is done through world sea routes. Sea state conditions are required to ensure safe navigation of ships. Also offshore operations can be done safely by monitoring prevailing sea state.

What is WaMoS II ?

To meet the above requirement, the Wave and Surface Current Monitoring System WaMoS II has been developed for real time measurement of directional ocean wave spectra. WaMoS II continuously provide wave data of the seas even under harsh weather conditions including low visibility and at night.

The WaMoS II software is loaded onto a standard PC, which is connected to a commercially available marine X-Band radar. The system extracts wave information from the radar images (up to 3 miles from the antenna) and by analyzing the spatial and temporal changes of the radar backscatter from the sea surface (sea clutter), determines directional wave and surface current information.

WaMoS II can operate automatically from unattended moored platforms, moving vessels and coastal sites. WaMoS II is the world’s most sophisticated operational wave radar monitoring system and is recognised by the international scientific community.

WaMoS II System diagram

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Image source:sea-image

Why to go for WaMoS II ?

  • is approved by the classification societies, DNV and GL
  • commercially available and is installed at a large number of fixed platforms in deep water, in coastal areas or from moving vessels
  • measure the surface waves in the same accuracy as in-situ sensors like a conventional wave rider buoy would do
  • can be used to measure waves in sea ice
  • is robust and easy to maintain
  • can be delivered as a portable system, so it can be easily moved from ship to ship, or put in a vehicle and driven along a coastal road collecting information
  • wave information from the radar images within a range of up to 3 miles from the antenna can be collected. The range depends on technical condition of the radar and installation configuration
  • the system can be connected to a network and save all the collected information and recorded results on a server. This stored data can be accessed directly at any time, via removable media, or on-line via modem/telephone or Internet
  • the system uses standard power supplies: 30W of power at either 110 or 220 volts. The PC with the LCD monitor needs approximate 200W; the radar e.g. Kelvin Hughes 300W (in standby 250W)
  • the system easily detects wave lengths from 20 metres to 600 metres, and wave periods from 5 seconds to 40 seconds.

WaMoS II limitations:

  • the minimum wave height which can be detected is about 0.50 – 0.75 m, with no limitation on the maximum
  • needs a minimum wind speed of about 3 m/second to provide sufficient wave and current information
  • the radar antenna should have a minimum free viewing angle of 180 degrees. A viewing angle of 270 degrees is ideal, but not necessary
  • the radar must operate in short pulse (near range), otherwise the sea clutter reflections are too weak
  • the antenna height is also an important aspect. Optimum performance is achieved with antenna height of as low as 7.5 metres from the surface, and up to 100 metres above the surface. Many coastal stations are installed with an antenna height between 25 m and 100 m
  • the system is under continuous development. The number of applications is being continuously expanded as new features are developed for individual wave detection, and high resolution surface current and bathymetry

If WaMoS II is installed in ships, the system requires the following NMEA inputs from the ship:

  • ship speed and direction (mandatory)
  • gyro compass position (mandatory) not GPS input
  • water depth (helpful, but not mandatory)
  • wind speed and direction (helpful, but not mandatory)
  • the inputs must comply with NMEA 0183 standard

Locations of WaMoS II stations installed and operating until December, 2007

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Source:oceanwaves

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