AbstractHigh frequency (HF) radars operate at radio frequencies between 3 and 30 MHz, where electromagnetic waves have the ability to propagate along the ocean surface and therefore to obtain information beyond the horizon. All the information measured by a HF radar corresponds to physical parameters of the upper couple of meters of the ocean surface. Today, HF radar systems are typically used along the coast, as they offer the unique opportunity to monitor the coastal area within a distance of 40 – 200 km. A HF radar system transmits electromagnetic waves and measures the backscatter intensity and speed of ocean waves. This information is primarily used to estimate surface currents and ocean wave properties. However, in the last decade, HF radars have also been shown to be extremely useful for several other applications such as surface wind measurements and tsunami monitoring, as well as vessel traffic support.