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The satellite looks down
Apr. 5th, 2005 06:56 pmGoogle 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 It raises the possibility that a business could get upset by, say, out-of-date images that show their building still under construction or entirely absent.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.