Delta_G:
I thought that was a scale stick about a 5th of the way in from the left. Running from about the 22.4 log down to the 27.6 log and through the 26.9 log. If you've got that and a decent alogrithm to draw the circles then it would be trivial for a real computer to measure them. But still not going to happen with Arduino.
Perhaps it is. Can't tell. I guess I can't see the trees because of the forest. Or something like that!
Paul