Meeting this goal will demand reliable, current data and information about how much water is stored in large lakes, rivers and reservoirs around the world which radar altimetry can provide. In the past, hydrological information could often be difficult to obtain by ground-based gauge instruments due to the inaccessibility of the region, the sparse distribution of gauge stations or the slow dissemination of data due to national policy.

Radar altimetry can avoid these obstacles because it is located on satellites 800 to 1300 kilometres above the Earth and is able to measure large lakes' surface water height to two centimetres accuracy and rivers to ten centimetres by sending 1800 separate radar pulses over bodies of water per second and recording how long their echoes take to bounce back. In addition, these data are available in near-real time.

Today there are several teams in the world involved in radar altimetry over inland water, using satellite data from ESA, NASA and the French Space Agency (CNES). Hydrologists from each of these research teams met at the '15 Years of Progress in Radar Altimetry' symposium, organised by ESA and the French Space Agency (CNES) in Venice Lido, Italy, from 13-18 March 2006, to discuss the abilities of past and current altimeters for monitoring the Earth's changing inland water resources.

Professor Philippa A. Berry of the UK's Earth and Planetary Remote Sensing Laboratory (EAPRS) at De Montfort University said: "This field has evolved rapidly over the past two decades. Initial work over a handful of large targets has now expanded to the current capability to monitor thousands of river and la
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Contact: Mariangela D'Acunto
mariangela.dacunto@esa.int
39-694-180-856
European Space Agency
22-Mar-2006