Overlap
Friday, 8th April 2005 by
One of the places on the map where the overlapping satellite images make for a weird perspective is in downtown Dallas. I've been staring at this for a while and I can't get my head around the perspective change.
Thanks Radical Bender.
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I agree this looks pretty weird. This must be the “seam” between two images -the extreme right edge of the left photo meets the left edge of the right photo. In any event that’s some clever stitching program to overlap the buildings like this.
No, thats not a perspective problem with the satellite, downtown Dallas is JUST THAT WAY. Crooked. period.
😉
Mmmm… social bookmarking…
If you scroll a little to the left of this photo, you can see the Kennedy Memorial. The book depository is the building just north of Elm Street where the road splits and the actual Kennedy monument is east of that between Main and Commerce (it looks like a tiny square building).
Hmm. It must be a time/stitching situation – because if you look at the shadows of the buildings to the right, the shadows fall to one direction.. but if you look to the left of the building, they’re going in a different direction.
I don’t know anything about satellite imagery – but I wonder if they pick a point and photograph the area but still centered on that point.. thus giving a top and side view to the buildings. This might explain this weird building. If it was the exact point that was chosen……. BUT like I said, I know nothing about satellite imagery.
Much better stitching than New York city, that’s for sure!
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Phoenix has some really bad alignment problems.
Maybe this category name should be spell-checked?
Oops, thanks Daniel Drucker!
Google Sightseeing
I discovered an interesting blog today called Google Sightseeing, a site which displays satellite images from around the world as found on the recently updated Google Maps service. The postings are broken down into a number of groups, I think…
Hey yawl, At this scale, this is not a satellite image, but a digital aerial image, taken from a plane. The buidling leans in such a way because of a phenomenon called “relief displacement” that causes tall objects to lean AWAY from the principal point of the photograph, or, the point at which the sensor/camera is DIRECTLY above the terrain. This type of distortion is a function of the flying height of the sensor, the height of the building itself, and the radial displacement — the distance of the top of the object away from the principal point.
relief dis. = (radial dis.)(height of object)/(flying height)
The reason we can say that this isnt a satellite image is because satellites are MUCH higher above the terrain, which would effectively bring the value of the above equation to close to zero (a small # divided by a large #). The reason why building are leaning in the opposite direction nearby is because they are part of an area that was imaged separately…They must have done some good mosiacking….
Fun, would like to see it in colour too.
Washington DC has some perspective weirdness centered on Constitution Ave NW, though not as prominent as the Dallas image (which would probably make Escher proud).
Perspective
^ overlapping satellite images, downtown Dallas
Google Sightseeing – Overlap
Related:
Via Just
Also some of these photos are years old. I’ve worked on the expansion of McCormick Place in Chicago for the past 2 years and according to the aerial photo I haven’t even begun to clear the site much less erect the steel structure.
Oh, man Eric!
Don’t let your manager find that image!!
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that one is very deceptive cause the shadows are correct. contrary to pastanous’ answer, satellite photos would create the same effect if the photo was taken when the satellite was at different angles (i.e. the satellite was in very different places in the sky/orbit)
-Greg
As Greg had stated, contrary to Pastanous’ post, a satellite image does not have to be taken from directly above the centerpoint of the image. It’s just a giant camera in space, it doesn’t always have to point straight down. There are several different ways to create a mosaic (the technical term for what most people are calling “stitching”) from multiple images. But, yeah, all of Google’s pics are from EarthSat, and are pretty well put together.
I found one in Boston- not nearly as good as the Dallas screw-up, but pretty nice.
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There are also a few minor, barely noticable ones in Seattle.
Whoops- my bad.
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This is definitly a stitching problem because the shadows are wrong, and the river changes color just to the South.
Hey, I work in that picture! =P