Waves and currents by X-band radar

Many offshore operations are critically dependent on the prevailing sea state. To enhance the safety of people, vessels, buildings and environment, routine sea state measurements are required. In coastal areas sea state measurements are needed to support weather and ship routing services. In addition in recent times, wave data gained growing importance in the protection of the coastal zone from eroding forces of wind, waves, and currents. To meet this increasing demand for sea state information, different wave sensors have been developed in the last decades. Special attention has also been given to the use of various remote sensing techniques to measure waves and surface currents. The ground based remote sensing technique described here is based on standard nautical X-band radar generally used for ship traffic control and navigation purposes. Wave measurements by X-Band radar systems are a reliable data source for supporting e.g. offshore as well as harbour operations or ship routing services.

It is known that under various conditions signatures of the sea surface are visible in the near range (< 3 nm) of nautical radar images. These signatures are known as sea clutter. The sea clutter is generated by hydrodynamic modulation, tilt modulation, and shadowing (Alpers et al., 1981). It is created by the backscatter of the transmitted electromagnetic waves from the short sea surface ripples (in the range of cm). see also: Use of ground based radar in hydrography