Stratification and sampling Clause Samples

Stratification and sampling. Due to the heterogeneity of Europe especially because of climatic and bio-geographical reasons a stratified validation shall be applied. In some products, classes that comprise only a small percentage of the total area of interest, a high number of samples is required in order to correctly assess 10 ▇▇▇▇://▇▇▇▇.▇▇▇▇▇▇▇▇▇▇.▇▇/pan-european omission errors (e.g. HRLs imperviousness, or wet land or permanent water bodies). From this entails that separate validations shall be carried out for different biogeographic strata. As an indication the bio-geographical regions of Europe map produced by the EEA can be used. ▇▇▇▇://▇▇▇.▇▇▇.▇▇▇▇▇▇.▇▇/data-and-maps/figures/biogeographical-regions-europe-2001. In case of a duly and scientifically justified underpinning this map is eligible for simplification or aggregation. Sampling strategies have to be proposed for each of the validation exercises. The number of samples shall be a compromise between accuracy (statistical representativity) and workload, whilst taking into account that the workload shall be a secondary consideration as compared to the requirement of ensuring a sound level of statistical representativity.