On Sun, 09 Sep 2007 19:52:30 +0200, Martin wrote:

On Sun, 09 Sep 2007 10:20:40 -0600, Newps wrote:


No, you just have to understand the realities of the process.

That's a bad analogy, we're not looking for one airplane in a sea of
other planes. Remove all the planes in the picture except one. Now try
and find the one plane.

and use software to compare old images with new ones to identify changes.

You'd have to have before and after photos with matching positions and view
angles of the satellites/aircraft or the photos you're comparing will be taken
from two different angles. You'd have to have the "before" photo taken at about
the same time of day and the same time of year, since the shapes of all the
shadows will be different, otherwise.

Finding a "before" picture might be a bit challenging. After all, it's
desert...how often is someone going to shoot a high-resolution picture of it?
The older the "before" picture is, the more natural changes will have occurred
and the more false positives. You'll have to hope no bushes have died off since
the previous photos were taken, that no new ones have grown, that the wind
hasn't pushed any dunes around, that no four-wheel-drive enthusiasts have cut
new tire tracks, etc. etc. etc. Having to chase down ~50,000 false positives
might slow things down a bit.

I'm a space (spacy?) guy, not a computer sciences type, but it seems to me that
the processing capability needed will be stretching the current technology.
Let's assume you've got a ground resolution of 3 feet. That's ~1760 pixels per
linear mile, 176,000 pixels per single row, or about 30 gigapixels total. Give
it a lousy 256-bit color, and that's about a 7.6 terabit image. Excuse me, TWO
7.6 terabit images, since we'll be comparing them.

Sure, the US Government might have the capability...but they'd be comparing
photos taken with same camera, taken just days or weeks apart, from the same
orbit, at the same time of day, etc. In any case, they are not likely to let a
set of civilians waltz in and borrow their computers.

Ron Wanttaja