Access to data is based on a principle of full, open and free access as established by the Copernicus data and information policy Regulation (EU) No 1159/2013 of 12 July 2013. This regulation establishes registration and licensing conditions for GMES/Copernicus users.

Free, full and open access to this data set is made on the conditions that:

1. When distributing or communicating Copernicus dedicated data and Copernicus service information to the public, users shall inform the public of the source of that data and information.

2. Users shall make sure not to convey the impression to the public that the user's activities are officially endorsed by the Union.

3. Where that data or information has been adapted or modified, the user shall clearly state this.

4. The data remain the sole property of the European Union. Any information and data produced in the framework of the action shall be the sole property of the European Union. Any communication and publication by the beneficiary shall acknowledge that the data were produced “with funding by the European Union”.

The Grassland Change Layer 2015-2018 at 20m spatial resolution is derived from the primary Pan-European Grassland Status Layers of the reference years 2015 (HRL GRA at 20m resolution) and 2018 (HRL GRA at 10m spatial resolution) and covers the area of EEA38 and the United Kingdom. The GRA Change Layer is the first of its kind indicating changes in grassland vegetation cover in five thematic classes. The production workflow consists of a map-to-map comparison of both years and takes adequate time features of both years as well as ploughing information from PLOUGH 2015 and 2018 back to the year 2010 into account.

Due to substantial transformations concerning resolution (20m to 10m), significantly enhanced data availability and therefore a refined technical approach, differences between the reference years of 2015 and 2018 are not always illustrating real changes in grassland vegetation cover but are sometimes technically induced. Areas differing in the years 2015 and 2018 that could not be verified as real change by the workflow are therefore labelled as unverified gain or loss areas.

Geometric accuracy (positioning scale): Less than one pixel (10m) according to ortho-rectified satellite image base (Sentinel-2 Level-2A) delivered by ESA.

Thematic target accuracy: The thematic accuracy has been assessed on the primary pan-European Change product and refers to classes 1-gain, 2-loss, 10-unchanged grassland in both years an 0-all non-grassland areas. Unverified areas are not part of the validation process. The unweighted overall accuracy is 88,97%. The weighted overall accuracy is 99,30% and considers the relative importance of all classes.

More information about this product can be found in their product specifications here: https://land.copernicus.eu/user-corner/technical-library/hrl-grassland-2018-user-manual.