The FengYun-3(FY-3) is Chinese new polar-orbiting, sun-synchronous meteorological satellite series planned to cover the duration of 2008~2021. The first two models FY-3A&B were launched in May 2008 and November 2010, respectively. The FY-3 satellite carries 11 instruments, the geolocation methods of their remote sensing image could be classified two types based on the instruments' scan geometry, paddle broom and conically scans. The representative instruments are the Medium Resolution Spectral Imager(MERSI) and the Micro-Wave Radiation Imager (MWRI).

MERSI is a paddle broom electro-optical instrument that uses the forward motion of the satellite to provide the along-track direction of scan. The geolocation approach for MERSI creates the spatial relationship model between the sensed data and the Earth based coordinate system, according to MERSI sensing geometry and the sensor's attitude and position. First, the line-of-sight vector from each detector of a band is calculated in the instrument coordinate system. The line-of-sight and satellite position are then rotated to the Earth Centered Rotating coordinates. The intersection of the line-of-sight with the WGS-84 ellipsoid is the calculated. An iterative search process is used to follow the line-of-sight from the instrument to the intersection of the terrain surface represented by a DEM.

Other instruments including VIRR, IRAS, MWTS, MWHS, ERM, TOU, SBUS are applied this geolocation approach. Compared the geolocation results with the true remote sensing image using the land-water mask, it shows that this geolocation methord for MERSI(250m) and other instruments achieves pixel accuracy.

MWRI conically scans with a fixed incident angle on the earth surface. It is the first time for Chinese remote sensor to use this scan mode. The geolocation method for MWRI's remote sensing image is based on its special scan geometry. The integrated coordinate systems and the specific relationships with these coordinate systems are defined. A spatial relationship model between the remote sensing data and the earth-based coordinate system is established. The 33 GCPs (Ground Control Points) which are in the regions of MWRI's observation have been collected and used to analyze the precision of the geolocation. By statistical analysis, the error along-track is about 1.5km, and the error along-scan is about 3.0km. It is obvious that this method fulfills the requirement of precision for MWRI whose space resolution exceeds 5km.