  Across globe and space agencies nations recognize the importance of
homogenized land cover information, prone to regular updates, both in the
context of thematic and spatial resolutions. Recent sensor advances and the
free distribution policy promote the utilization of spaceborne products in an
unprecedented pace into an increasingly wider range of applications. Ensuring
credibility to the users is a major enabler in this process. To this end this
study contributes with a systematic accuracy performance measurement and
continental/global land cover layers' inter-comparison moving towards
confidence built up. Confidence levels during validation and a weighted overall
accuracy assessment were applied. Google Earth imagery was employed to assess
the accuracy of three land cover products, i.e., Globeland30, HRLs and CLC
2012, for the years 2010 and 2012. Reported rates indicate a minimum weighted
overall accuracy of 84%. Specific classes' performance deviations from the
general trend were noted and discussed on the basis of an unbiased sampling
approach. By integrating confidence levels during the ground truth annotation,
stratified sampling on the several Corine Level 3 subclasses and the weighted
overall accuracy assessment, the different aspects of the considered land cover
products can be highlighted more objectively.
