The harmonization of operational data products and the creation of higher level information products such as global maps and time series (from different sensor sources) are required to satisfy the operational service requirements of the societal benefit areas as outlined in the GEOSS implementation plan. The CEOS working group on calibration and validation (WGCV) concentrates on defining standards and procedures aimed at allowing for the inter-comparison and ultimate utilization of data from all Earth observing platforms, both current and future. WGCV strives to establish common approaches to validation, calibration and data exchange formats to ensure effective cooperative use of all CEOS member space assets in addressing important global scale problems. This paper reviews the WGCV data assurance strategy, detailed system element requirements to guarantee data quality, and current WGCV activities for the generation and validation of products.