I was exploring some unrelated things (as usual), and I found an interesting
shadow clock that was easy to model

https://www.dezeen.com/2015/10/23/breaded-escalope-touch-shadow-clock-vienna-design-week-2015/

And then I was noticing how the sun came into my apartment, and thinking back on
a solar energy model I made a few years ago, and Ingo's sunpos.inc file, and I
recalled that an ordinary watch can be used as a makeshift compass.

Orient the hour hand to point at the sun (accurately done with a blade of grass
to cast a shadow across the hour hand) and then divide the angle between the
hour hand and the 12:00 mark.  That's roughly South.

I wanted to see how it worked, and get an idea of how far off it would be.

So naturally I modeled it in POV-Ray   :)

Seems to work ok, and be off by +/- 30 degrees - dead on at noon.

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