Ocean and Coastal Altimetry


Satellite radar altimetry is capable of taking an accurate measurement of the height for the sea surface along the ground track of the satellite. From that measurement oceanographers can study open-ocean and coastal currents, and monitor sea level variations, including extreme events like storm surges. Altimetry also allows an estimate of the significant wave height and surface wind. To retrieve these measurements from the raw radar echoes requires some processing: first the echoes (called normally ‘waveforms’) must be fitted (‘retracked’) with a waveform model, then (for sea surface height only) a number of instrumental, atmospheric and surface corrections must be applied. This processing is more challenging in the coastal zone, say within 30 km from land, and until a few years ago data collected close to the coast were just not used. But in the last few years coastal-specific retracking and corrections have been developed and coastal altimetry data are starting to become available.

For the ocean and coastal altimetry application we are developing a processor that ingests raw altimetric data, reprocesses them with the latest techniques, and provides the data to the users at high-rate (20 samples per second along the track, corresponding to ~300 m).

The user will be able to select his/her area of study in a number of ways (geographical coordinates, .kmz file, select from a list of pre-set regions). Then the user will select the time window, and the system will find and show (on a map and as a structured list) all available satellite overpasses over that time and geographical region. At this point the user can select all the data from one or more satellites, or only some specific passes and then run the processor.

The processed data are finally made available for download in a netCDF format. As a bare minimum every netCDF file contains longitude, latitude and time coordinates of the data, plus at least one of sea surface height anomaly, significant wave height or wind.