Radar altimetry revolutionises the study of the ocean     Scientists with an interest in radar altimetry have gathered from around the world in Italy at the ‘15 Years of Progress in Radar Altimetry’ symposium. Sponsored by ESA and the French Space Agency (CNES), the symposium is being held in Venice Lido from 13 to 18 March 2006.   Altimetry-derived mean dynamic topography of the sea surface. This is the mean height of the sea surface relative to the geoid, or the theoretical surface of equal gravity around Earth.   An unusual view of St. Mark's Square flooded by high water, that reached 1.11 meters above the medium sea in Venice Thursday, November 14, 1996.   Like its predecessor ERS-1 (launched in July 1991 by Ariane 4 and successfully put into orbit at an altitude of some 780 km), the ERS-2 satellite launched on 21.04.95 by Ariane 4, monitors the Earth day and night under all weather conditions thanks to its powerful sharp-eyed, cloud-piercing radars. ERS-2 also carries an instrument to help monitor the ozone layer around the Earth. Release date: 17 March 2006