Sub-pixel accuracy evaluation of FY-3D MERSI-2 geolocation based on OLI reference imagery

The geolocation quality of satellite observation datasets is causally related to the credibility of operational products. The twice-daily global Earth observations provided by FY-3D/MERSI-2 (FengYun-3D/MEdium Resolution Spectral Imager II) have been used to generate various remote sensing application products, but their geolocation performance has not yet been documented, while the comprehensive analysis of geometric accuracy provides important guidance for improving geolocation accuracy and data application in the future. In this paper, a combination of phase-only correlation and anomaly isolation techniques was used to design a robust algorithm of sub-pixel geolocation displacement detection for MERSI-2 data with 1 km spatial resolution. Utilizing MERSI-2 data from three typical regions and monthly Landsat 8 OLI (Operational Land Imager) data synthesized by Google Earth Engine (GEE), an exhaustive presentation of how the developed method quantifies the geometric displacements of the Level 1 dataset to along-track and cross-track directions is described, ultimately revealing the deterioration of MERSI-2 on-orbit geolocation performance. During the 17 months of official operational products, the geolocation error increases by a factor of 1.13 in along-track direction and 1.56 in cross-track direction. But approximately 70% of the geometric displacements remain within +/- 300 m in both along-track and cross-track directions, while about 92% are within +/- 500 m. This method reliably ascertains that the geolocation accuracy of MERSI-2 matches within 1/2 Instantaneous Field of View (IFOV).