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UCSB Ocean Surface Currents Mapping Project - How It Works


We use High-frequency (HF) radio waves, sometimes called CODAR (Coastal Ocean Dynamic Application Radar), which scatter off the surface of the ocean, and using sophisticated algorithms relating to Doppler shift one can calculate basic speed and direction of the surface currents.
  1. At each radio station location, we have two antennas:
    • The transmit whip antenna is omni-directional. Since the surface of the ocean is electrically conductive, the transmitted radio waves (3-50 MHz in 4-18 minute intervals) can travel beyond line-of-sight.
    • The receive antenna has three antennas oriented perpendicularly in the x, y and z-axes. If a wave is one half the wavelength of our radio wavelength we get a return signal from it and can calculate its perpendicular (directly away or towards the antenna) speed.

    We can thus determine the movement of 3-30m ocean waves because we can determine the following three pieces of information:
    1. Distance -- By the time delay of the return signal from when it was transmitted.
    2. Speed -- From Doppler shift of the returned signal -- this shift includes the theoretical speed of the wave plus the ocean currents.
    3. Bearing -- From a complex 'direction-finding' (DF) algorithm.

  2. With two radios located at different locations which can look at the same area of ocean, and their different viewing angles allow us to combine each radio's radial velocities and translate that into a 2D map of the upper (1-2m) surface currents.
  3. We then take this near real-time data and post maps on our website!

Users of our data include:
We use CODAROS SeaSonde HF radios, and they have a good summary of this technology at codaros.com.