The original images are more than 110mb each (8640×4320 24-bit pixels).
To permit interactive access in Earth Viewer, the images were compressed to reduce the number of colours during the day to 1024, and during the night to 64.
This reduces the image database to a large, but manageable, 74.6mb.
The ultimate resolution of the database is about 4.6 kilometres per pixel.
The cloud cover, colour weather, and water vapour density images are generated on the fly, every three hours, from the whole-Earth weather satellite composites.
The original images, made available by the University of Wisconsin-Madison Space Science and Engineering Center, have additional fine detail which had to be sacrificed to allow quick response to Earth Viewer requests.