Every night a pass goes over each archived day and measures what the frames show without being told: when first light actually shows up against the astronomical sunrise (how thick the marine layer is at the horizon), a smoke index from the sky's red/blue ratio, how green the big tree is, how far you can really see (from the contrast of the far buildings), the campus's hourly motion, and a ledger of every night lamp, with the nights one goes dark.
The camera has moved to different buildings and windows before. Scene fingerprints catch each move, and no metric gets compared across one.
More: the live archive · FogCam history