The satellite looks down
Apr. 5th, 2005 06:56 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
mmcirvinGoogle Maps now has photorealistic imagery gotten in Google's acquisition of Keyhole (the "Satellite" link off to the right). It's pretty cool. I wonder if these are all really satellite images or if some of them are from airplanes; they're about as detailed as other such databases I've seen—as before, the standout thing here is not the database but the Google Maps user interface.
One odd thing about it is the chosen projection. The street maps they had from the beginning seem to be in some form of simple latitude/longitude projection, scaled so that the aspect ratio is 1:1 somewhere in the middle of the US. It's sensible enough for applications that involve picking out coordinates, though things get kind of distorted in northern Canada.
The satellite images, though, are all squashed vertically by a factor of maybe two-thirds relative to the map images. I think they're going for a fake perspective effect to square with the shadowed map pins and bubbles. I suppose it also lets them fit more imagery on the screen. But it's kind of disconcerting in that features away from the center point don't line up when you switch between the map and satellite views. I think I'd have preferred a common scaling.
It's also interesting that you can still use the business-search feature and such on the satellite images. It raises the possibility that a business could get upset by, say, out-of-date images that show their building still under construction or entirely absent.
Update: Aha, I see what's up. The satellite images are superimposed on a map covering the entire world (though there isn't actually detailed imagery for the whole world), and that map has the 1:1 aspect ratio at the equator, so naturally ratios are squashed in North America. I think they need to think some more about how to handle the map projection. This is actually a case where a conformal projection like the much-maligned Mercator might make sense. Or, better, figure out some way to reproject the images for different center points, at least to cover various large ranges of latitude.
One odd thing about it is the chosen projection. The street maps they had from the beginning seem to be in some form of simple latitude/longitude projection, scaled so that the aspect ratio is 1:1 somewhere in the middle of the US. It's sensible enough for applications that involve picking out coordinates, though things get kind of distorted in northern Canada.
The satellite images, though, are all squashed vertically by a factor of maybe two-thirds relative to the map images. I think they're going for a fake perspective effect to square with the shadowed map pins and bubbles. I suppose it also lets them fit more imagery on the screen. But it's kind of disconcerting in that features away from the center point don't line up when you switch between the map and satellite views. I think I'd have preferred a common scaling.
It's also interesting that you can still use the business-search feature and such on the satellite images. It raises the possibility that a business could get upset by, say, out-of-date images that show their building still under construction or entirely absent.
Update: Aha, I see what's up. The satellite images are superimposed on a map covering the entire world (though there isn't actually detailed imagery for the whole world), and that map has the 1:1 aspect ratio at the equator, so naturally ratios are squashed in North America. I think they need to think some more about how to handle the map projection. This is actually a case where a conformal projection like the much-maligned Mercator might make sense. Or, better, figure out some way to reproject the images for different center points, at least to cover various large ranges of latitude.
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Date: 2005-04-05 04:30 pm (UTC)The highest resolution color photography is the best I've seen yet on the web. Zoom in on "Skaneateles, NY" for an example. These high resolution patches occur in oddly isolated places, though. If you back out to see New York, you find Skaneateles is one of a number of places where a small, isolated high-res rectangle is surrounded by lower-res stuff. (Zoom out even further and you'll see a Massachusetts-shaped region of high resolution.) The city of Syracuse seems to be mostly monochrome high-res, with little odd rectangles of low-res color here and there. North of Syracuse (search for Redfield, NY and go north from there) the "Tug Hill" region is a big rectangle of high-res color -- even though, as you can see by the map, it contains no major roads and almost no settlement. (The fact that they get 300 or more inches of snow most winters might have something to do with that -- even Syracusans think that's nuts.) I wonder if that's because some logging company paid for high res coverage, which Google inherited.
But around Parish, NY -- where I live -- and apparently in much of the state if not the country, the photography is color but significantly lower resolution than what you'd find from , e.g., Terraserver.
Another interesting thing is that the photography extends beyond the realm covered by the maps. In fact you can zoom out to see the whole world, though I don't know how much of that is actual photography; presumably the ocean floor topography isn't. Zooming in reveals most of the world doesn't get down to very good resolution at all, but the part that is covered at decent resolution isn't just the US and Canada. It includes Iceland, Mexico and Central America, the north shore of South America, and at least parts of the Caribbean -- including, I was amused to note, Cuba. If you want to have a do-it-yourself Bay of Pigs invasion, I suppose this is a good place to start your planning. <-- NOTE TO FEDERAL AUTHORITIES: JOKE
I do wish it was easier to come up with a URL for a map view you find by clicking and dragging -- "Link to this page" doesn't do that. And, dammit, is there any reason on earth not to provide a scale? And, for the photos, the resolution in meters per pixel?
Still, sweet interface and great color high resolution in many places make this a Really Cool Thing In the Making.
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Date: 2005-04-05 04:34 pm (UTC)The combination of images taken under different conditions with wildly different color palettes produces an interesting patchwork effect.
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Date: 2005-04-05 04:36 pm (UTC)no subject
Date: 2005-04-06 07:31 am (UTC)(For fun, I took some map images I have of my home town and made a Google Maps interface for it. Since I also had aerial photo data, I added an option to show that too. You can look at it here, but it's on my home machine and ADSL connection so it'll be slow, or not available at all if my computer is off.)