I sampled a dozen or so webcams from around the world for a couple of years. I assembled 16-pixel square images in to mosaics showing variations in sky color throughout the day. site
This work was inspired by my Sky Color Monitor.
I sampled once an hour and then rolled results up into an accumulating image every night.
35 * * * * public_html/sky/sample 50 15 * * * public_html/sky/nightly
I learned how to deal with all maner of outages in order to make my sampling robust.
#!/bin/bash cd ~ward/public_html/sky for d in data/ * do ( cd $d if test -s tile.ppm then ./tile | pnmcat -tb tile.ppm - >$$.ppm else ./tile >$$.ppm fi if test -s $$.ppm then if pnmscale -yscale .1 $$.ppm | \ cjpeg >tile.jpg then mv $$.ppm tile.ppm else echo $d: $$.ppm discarded fi else echo $d: no $$.ppm produced fi ) done
I would repeat the last sample if a camera were not available. Some cameras would go missing for days and then comeback. Others went missing period.
In Tromso boarding the ferry at midnight for a cruise/workshop that ended in Bergen.
Only two or three cameras would stay in position for the years it took to make interesting pictures. I especially liked the camera in Tromso, Norway, situated in a university window looking across the harbor.
I'd been to Tromso and knew how light it was at midnight.
The admin that ran this thing kept his computer up and his camera in position years on end.
These are two-year, 24-hour a day images assembled from various places around the globe. Latitude affects the vertical position of the daylight region, longitude the magnitude of the variation throughout the year. Samples are taken hourly working top down from 0:00 GMT.