Copernicus Global Land Hot Spot Monitoring Service – Accuracy Assessment and Area Estimation Approach
Publication from Digital
Heinz Gallaun, Gabriel Jaffrain, Adrien Moiret, Andreas Brink, Zoltan Szantoi, Stefan Kleeschulte, Mathias Schardt, Conrad Bielski
ESA-Worldcover 2017 worldcover2017.esa.int/, 2017
The main objective of the Copernicus Global Land – Hot Spot Monitoring Service is to provide detailed land information on specific areas of interest, including protected areas or hot spots for biodiversity and land degradation. For such areas of interest, land cover and land cover change products which are mainly derived from medium (Landsat, Sentinel2) and high resolution satellite data are made available to global users. The service directly supports field projects and policies developed by the European Union (EU) in the framework of EU’s international policy interests. It is coordinated by the Joint Research Center of the European Commission and answers ad-hoc requests and focus mainly within the domain of the sustainable management of natural resources.
Comprehensive, independent validation and accuracy assessment of all thematic map products is performed before providing the land cover and land cover change products to the global users. The following rigorous methodology is conducted: Spatial, temporal and logical consistency is assessed by determination of the positional accuracy, the assessment of the validity of data with respect to time, and the logical consistency of the data e.g. topology, attribution and logical relationships.
A Qualitative-systematic accuracy assessment is performed wall-to-wall by a systematic visual examination of the land cover and land cover change maps within a geographic information system and their accuracies are documented in terms of type of errors. For quantitative accuracy assessment, a stratified random sampling approach is implemented which is based on inclusion probabilities. A web-based interpretation tool based on PostgreSQL is implemented which provides high resolution time series imagery e.g. from Sentinel 2, derived temporal trajectories of reflection, and ancillary information in addition to the very high resolution imagery. In order to quantify the uncertainty of the derived accuracy measures, confidence intervals are derived by analytic formulas as well as by applying bootstrapping. Area Estimation is performed according to the requirements for international reporting. In general, the errors of omission and errors of commission are not equal and such bias shows up in the course of the quantitative accuracy assessment. As the implemented approach applies probability sampling and the error matrix is based on inclusion probabilities, area estimates are directly derived from the error matrix. The area estimates are complemented by confidence intervals. The approach and methodology will be discussed in detail on the basis of a systematic accuracy assessment and area estimation results for sites in Africa which are the focus in the first year of implementation of the Copernicus Global Land Hot Spot Monitoring Service.