A group of scientists have produced the first global geologic map of Jupiter moon Ganymede. The scientists led by Geoffery Collins of Wheaton College combined the best images obtained during flybys conducted by NASA’s Voyager 1 and 2 spacecraft (1979) and Galileo orbiter (1995 to 2003) and is now published by the U. S. Geological Survey as a global map.
I downloaded the map from the USGS site. I clicked on the image at the site and wow what a nice job they did. The image above will make a lot more sense for you if you check out the links at the USGS page. I am heading over to get the database, that should be excellent.