A reference sample database for the accuracy assessment of medium spatial resolution land cover products in Portugal

This paper introduces a reference sample database that is being developed by the Remote Sensing Unit of the Portuguese Geographic Institute for the accuracy assessment of medium scale land cover products in Portugal. The goal is to provide the worldwide remote sensing community with sufficient data for the accurate estimation of overall and per class proportions of correctly classified area in regional and global land cover products at this part of the globe. This is a massive database that encloses various descriptive attributes for each sample observation, namely primary and alternate reference land cover labels, nominally scored interpretation ratings and location confidence ratings. We present in detail the attached land cover nomenclature and the database design, i.e. the sampling design used to collect sample observations, as well as the process used to identify the most pertinent reference land cover label for each observation. In addition, we briefly describe some statistics about attribute information that was recorded for each observation and that can be used as auxiliary information for the accuracy assessment of land cover products.