Radar measures currents in seas and rivers

Researchers are developing new flow measurement technology in coastal waters and rivers

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Satellites might soon be used for flow measurements in coastal waters and rivers. For scientists from the Institute of Oceanography (IfM) of the University of Hamburg have developed a new, powerful radar method - the so-called "Along-Track InSAR" - which delivers images of flow fields, for example in the Wadden Sea.


After successful tests, first routine measurements could be carried out by the German satellite TerraSAR-X, which will probably start in April 2007. The Along-Track InSAR uses differences between two radar images taken within milliseconds for direct velocity measurements. The measurements work independently of daylight, clouds and fog. The measuring principle is based on the so-called Doppler effect, as in a police radar.

Roland Romeiser of the IfM and Hartmut Runge of the German Aerospace Center (DLR) were able to prove by simulation calculations that the radar of TerraSAR-X will allow flow measurements with resolutions of about 400 to 1200 meters. If the new technology proves to be successful, satellite missions can be realized with further improved instruments.

Many applications

The researchers from the IfM, including Romeiser, Professor Detlef Stammer and Steffen Gr├╝nler, are currently planning a worldwide monitoring of river outflows (amount of water per unit of time). Temporal changes in river outflows are of great interest, for example, to oceanographers, climatologists and hydrologists, partly because the data available so far are very incomplete. display

Other along-track InSAR applications include site optimization for novel flow power plants and monitoring changes in underwater soil topography in shallow waters that are emerging in the surface flow field.

First airborne experiments were undertaken by US scientists in the late 1980s. At the IfM, where extensive experience with the interpretation of other radar data existed, from 1993 the along-track InSAR mapping of flow fields and ocean waves was theoretically investigated and a computer model developed to simulate the imaging process.

(idw - University Hamburg, 03.04.2007 - DLO)