images from terrestrial satellites in earth orbit
The original images of the Earth by day and night are 8640×4320 24-bit pixels: more than 110 megabytes each.
To permit interactive access in Earth Viewer, the images were compressed to reduce the number of colours in the day side image to 1024 and the night side to 64.
This reduces the image database to a large, but manageable, 74.6 megabytes.
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 made available by the University of Wisconsin-Madison Space Science and Engineering Center.
The original images and products based upon them have additional fine detail which had to be sacrificed to allow quick response to Earth Viewer requests.