The On Line Validation Exercise (OLIVE) Tool: a CEOS/LPV initiative for validation of global land products

The OLIVE (On Line Interactive Validation Exercise) system enables transparent and traceable validation and inter-comparison of EO land products (LAI, FAPAR, FCOVER). The ultimate objective of OLIVE is to provide consistent and reliable information on the accuracy and associated uncertainty of EO products. The validation exercise follows the guidelines proposed by CEOS/LPV and allows for regular updates when new versions or products are available. OLIVE is accessible to the whole EO community which can run validation exercises, including existing or new products. The validation process involves several criterions listed hereafter: (i) continuity of products, i.e. evaluation of the spatial and temporal distribution of missing values,(ii) accuracy assessment achieved by comparing the product value derived from satellite observations to ground measurements of the corresponding biophysical variable (i.e. direct validation) (iii) precision assessment, mainly regarding the temporal and spatial consistency, including the long term temporal stability mandatory for several applications, and (iv) intercomparison between currently existing products. OLIVE is a web platform and provides three main functionalities: 1. Easy and transparent access to validation exercise results, including product definition, description of the validation process and associated data. 2. Evaluate new EO products/versions developed by any producer. Formats required for the candidate input product are described in details. The validation can be run in two modes: (i) the 'private' mode for which the validation results are only visible to this user. This mode is dedicated to perform tests when the product may not be mature enough for public scrutiny; (ii) the 'public' mode, for more mature products, where the results are published on the system and accessible to the community. In the latter case, the data used for the validation are stored on the system and available to the community for inter-comparison exercises. 3. Propose new sites with ground measurements to be included in the direct validation. In this case, the candidate sites are required in a specified format with associated metadata and documentation. A review committee will evaluate the proposed sites to verify that the required criteria are fulfilled and determine whether or not the proposed sites will be included with the other sites used for direct validation. The OLIVE system is hosted by the CEOS Cal/Val portal. It is implemented for validation of LAI and FAPAR for a selection of currently available products (MODIS, CYCLOPES, GEOLAND) but will be extendable to other land products such as albedo.