Validation Site

A validation site is a fixed, well-instrumented reference location used to assess and calibrate satellite product accuracy against in-situ ground truth. For ocean altimetry, permanent facilities such as Gavdos and the Crete sites in Greece and the Bass Strait and Harvest sites compare satellite sea-surface-height retrievals with co-located tide gauges, GNSS, and transponders, isolating instrument bias to centimeter level. Cal/val sites underpin the CEOS calibration framework and support missions including Jason-3, Sentinel-3, Sentinel-6, and SWOT. The site provides the absolute reference that ties a remote retrieval to a measured quantity, without which a satellite drift is invisible.