> > Could you use the regularity of the window spacing on the
> > train carriages to measure speed by detecting variations in
> > reflected light?
>=20
> I was just thinking the very same, using a low-power IR laser
> perhaps so as to not startle passengers

You probably don't even need a laser, just a source of suitable light,
and measure the speed of the train by correlation of the image. This
technique is used for measuring the speed of red hot steel in steel
mills I believe, along with other applications.
--=20
Scanned by iCritical.

--=20
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