On possible technique would be to use a linear array of photocells.=20
Basically, you copy the seismogram onto lithographic film, then run the
film past a light bar on one side with the photocells on the back.=20
You could also - with loss of resolution - do the same thing with both
the light source and photocell array "looking" at the front. =20

You can in fact digitize those old paper records - but I have no idea
if anyone is actually doing so.  One problem that jumps out at me is
the overlap of traces on the helicorders - I'm not sure (at least
having had only my second cup of coffee) how to disambiguate
overlapping traces during large events.=20

Tom G.



On Mon, 31 Jul 2000, you wrote:

>=20
> Would anyone have any idea how this "ingenious photo-electric device" f=
or
> converting paper traces into voltage signals might work?  I'm guessing
> there must be some sort of activity in the field of Seismology to digit=
ize
> old paper seismograms, so maybe there are actual commercial devices to =
do
> the work now.
>=20
> Regards,
> Ted Blank
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