On Wed, 04 Aug 1999 16:32:00 +0200, Remco de Korte wrote:
>I was
>> looking for free or inexpensive software that could be used with a digital
>> camera to automate the process, so they can see how it's done in the digital
>> age.
>
>And derive them of the fun?

Not at all.  They'd still do it the old way and have the opportunity to
get messy, they'd also get to see another way of doing the same thing, 
perhaps with some cool POV visualization and some more advanced watershed 
management stuff (flow lines, etc.) thrown in courtesy of GRASS.

>I thought it shouldn't be hard to make such a program if you know exactly what
>to use it for (straightforward). Then I thought, the problem is probably not the
>program (that's just calculating a parallax or what-do-you-call-it), but the
>photography. You have to know the exact location of the camera at two points.
>Also, you'll probably need quite a high resolution to get a result with a
>reasonable amount of details. If the photo-part is not a problem I can't imagine
>that the programming-part would be (not for you, would it?).

High resolution is likely to be necessary, yes.  I'm not sure about knowing 
the exact location of the camera.  Separation distance, distance from the 
terrain, and some info about lens geometry might be necessary, true, unless 
you were willing to cheat and feed it elevations for the summit and the 
lowlands and let it scale its results to fit.  I think even USGS cheats by 
putting reflective markers at known locations in the area to be photographed,
so that rectification can take place separate from stereocorrelation.

Unfortunately, I did some experiments and it's much more difficult than it 
looks to recover the parallax information.  And of course I wouldn't want 
such a project to take time away from valuable pursuits like the superpatch. :)

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