Wednesday, April 10, 2013

Melting El Capitan

Take a look at the image below, which compares El Capitan (coordinates 37.729639,-119.63662) on Google, Yahoo, and Bing maps. You see something very interesting, which reveals something about the stitching algorithms used by all the big tech companies here. (Disclosure: I work at Google, but I have no idea how Maps are actually implemented, I don't work on Geo stuff).

Specifically, that they don't expect almost perfectly vertical surfaces. El Capitan is unusual in that it's pretty much straight up and down. When dealing with imagery that was acquired via a satellite, it's unclear how to convert that into an image which has a different perspective.

So what you're really seeing here is the angle from which the satellite took the picture. Google from the North-by-North-East, Yahoo from the East, Bing from the North. They can't figure out what to fill in that unknown divide-by-zero kind of space, so they bleed in from around it to avoid having a map with a bunch of black holes in it.