The goal of the keogram is to give a quick overview of sky conditions so you can see if there were clouds, aurora, or other interesting activity. No information is discarded, as the user keeps all of the data, the keogram is just a way of identifying which pictures might have something interesting.

The year long keogram presents even less data, as it's just the centerline of the keogram for each day. So, essentially just the center pixel of each image. Still gives a good overview of what the sky conditions were like throughout the year.