World Sunlight Map: How it works – die.net
The World Sunlight Map provides a computer-generated approximation of what the earth currently looks like. While less impressive than actually being into orbit, this is much more accessible to most of us.
I start with cloudless images of the earth during the day (from a pair of NASA satellites) and night (from a DoD program to map city lights). Every 3 hours, I download a composite cloud image based on data from weather satellites all over the world. And every half hour, these images are composited and mapped onto a sphere by xplanet according to the relative position of the sun. The flat maps are post-processed by ImageMagick to cut off the 15 degrees nearest the north and south poles where cloud data is unavailable.