GCPIX: Ground Control Point (GCP) Intercomparison eXercise, started in 2025, aiming to unify CEOS Agency GCP sharing.

The initiative, led by CEOS, aims to develop a harmonized global GCP database for high-resolution (HR, 4-30m GSD) and very high-resolution (VHR, < 4m GSD) optical Earth observation data. The project addresses critical challenges in spatial data interoperability, emphasizing geolocation accuracy and geometric distortion correction for seamless integration of multi-source datasets.

Key technical steps include standardizing terminology (e.g., GCP, orthorectification), defining quality criteria for individual GCPs (resolution, location uncertainty, wavelength) and ensembles (spatial density), and establishing “fitness for purpose” thresholds for specific data categories (e.g., VHR, SAR). The initiative builds on prior work like AGRI (Australia’s geographic reference imagery) and EDAP (ESA’s geometric calibration activities) to harmonize existing CEOS agency datasets into a unified database hosted e.g. by the TMSG and IVOS sub-groups of WGCV. A cloud-based platform will facilitate data sharing, while protocols for documenting and sharing GCP libraries will ensure consistency. The project prioritizes identifying gaps in coverage and quality, densifying VHR data, and integrating DEMs or reference chips where feasible