Colocation procedures and analysis developed at IFREMER LOS-CERSAT allow long term monitoring of altimeter significant wave height(SWH). Trends and biases, up to several tens of centimeters, between the Geophysical Data Records issued from the various altimetermissions, were identified and corrections were proposed(Queffeulou 2004). Since that time data from new buoy networks were acquired, increasing the size of the data set, particularly for JASON and ENVISAT. Updated validation results differ, slightly, from the previous one sand improve the cross-altimeter SWH measurement consistency. But significant differences are observed, at high SWH, within the various buoy networks, which could raise the question of the choice for a reference SWH measurement.

The user requirements of IFREMER LOS within the GlobWave project are:

• Easy access to wave data from in-situ, satellite and models. Homogeneous altimeter database (Hs, Tp, backscatter, wind speed). SAR data homogenisation. Friendly access, establish common vocabulary
• Info on validation and accuracy
• tools for colocating data
• access to wind, bathymetry and surface current data
• GlobWAVE to select super-sites (HR-DDS)