Would it be possible to calculate these parameters with a panoramic creation
package like panotools?

http://wiki.panotools.org/Lens_correction_model

It calculates a value for field of view, but I didn't notice an actual focal
length parameter.  Maybe this is easy to associate?

One benefit is that you are calculating using image overlap, which may be
easier than trying to reference to a recent photo.

-Jamie

On Thu, Apr 10, 2008 at 9:53 AM, Vincent Bain <[EMAIL PROTECTED]> wrote:

> May it be a stupid suggestion, but did you try to contact anyone at the
> USGS ? perhaps they maintain data from these old times... (here in
> France IGN is always helpful, and can provide answers to such historical
> requests)
>
> Vincent.
>
> Le jeudi 10 avril 2008 à 18:33 +0200, Markus Neteler a écrit :
> > On Thu, Apr 10, 2008 at 5:29 PM, Shaun & Melissa Busler
> > <[EMAIL PROTECTED]> wrote:
> > > Unfortunately, the focal length of the camera is not on the photo
> border.
> > > The photo must be too old.  Do you have any recommendations on what
> focal
> > > length I should try?  It was taken in 1939 for the USDA Agricultural
> > > Adjustment Administration.
> >
> > You could try 150mm or 305mm. In fact, i.ortho.photo is quite robust,
> > just try and hope that it converges.
> >
> > (and/or: Maybe someone on the PROJ4 list knows.)
> >
> > Markus
> > _______________________________________________
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> > grass-user@lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-user
> >
>
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