ABSTRACT
The original purpose for which radar was developed was the detection of targets such as airplanes and ships. In remote sensing applications, over-theland radars are used to study spatial variations in the surface of the land and also the rather slow temporal variations on the land surface. Before the advent of remote sensing techniques, data on sea state and wind speeds at sea were obtained from ships and buoys and were accordingly only available for a sparse array of points. Wave heights were often simply estimated by an observer standing on the deck of a ship. As soon as radar was invented, scientists found that, at low elevation angles, surrounding objects and terrain caused large echoes and often obliterated genuine targets; this is the wellknown phenomenon
clutter.
