Page History

...

Recommendation Details: When producing geolocated image data derived from satellite-based or airborne remote sensing instruments, we recommend defining the projection ellipsoid to be the same as the datum used by the remote sensing system to define geodetic latitude and longitude.  Specific details depend on the selected file format and metadata conventions.  Examples provided in this recommendation use GeoTIFF terminology, but the recommendation also applies to other formats and metadata conventions.  For example, when using GeoTIFF to represent content in a Projected Coordinate Reference System (PCRS), the projection ellipsoid should be the same as the Geodetic Reference Frame (datum) used by the remote sensing system.  For many currently operating satellite instruments, the reported geolocation is referenced to the World Geodetic System (WGS) 1984 datum.  Airborne instruments that are geolocated using GPS instruments are also referenced to WGS84.  When geolocated data from one of these instruments are used to create derived geophysical products, data producers may choose a PCRS that includes a map projection based on a reference ellipsoid.  To ensure maximum interoperability when transforming such data products, we recommend choosing the PCRS map projection ellipsoid to match the underlying Geodetic Reference Frame (datum).  This will minimize potential for geolocation error with overlays of related geolocated information such as coastlines or comparison data products. 

In the following discussion, we use the ISO19111 terminology explained in Section 2.1.2 and Appendix A of Iliffe and Lott (2008):

...