part way, maybe 90 degrees. Ah-HAH! It's the old effect of blue sky light
being fairly highly polarized, especially in the morning and evening. This
interacts with the polarized filter overlaying the LCD screen, to give a
directional sensitivity that doesn't happen under artificial lighting!
This only works in the shade (contrary to the anti-sundial ideas), with
clear sky. Hold the cell phone or PDA horizontally in front of you, while
you rotate through 360 degrees. You should see two distinct peaks and two
valleys of shade on the screen. The lighter condition corrsponded - on my
phone - to North and South.
This sounds quite well but does anybody know if it is accurate within,
say, +/- 15 deg and if it can
be done with any LCD screen (big enough and in the same shade
conditions, of course)?
Best regards,
Anselmo
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