M.C. Escher, a 20th century Dutch artist with an eye for geometric oddities, created famous optical illusions. You may have seen his images of stairs that look normal at first glance, but look again and you find that they twist in seemingly impossible ways. The Escher effect in Google refers to the way that some Google Earth images seem to warp in strange ways -- rather like an Escher painting.
Escher Effect
The Escher effect is most evident in cities with lots of skyscrapers. Scrolling through the overhead city shots in Google Earth the building arrangements may suddenly look a little odd. Some shadows may suddenly disappear. While some skyscrapers lean in one direction, one or two appear to lean the other way, or lean at a far greater angle than the other. This gives the impression of bending the laws of physics -- in much the same way that M. C. Escher's illustrations warped geometry and space.
Google Earth
Google Maps is the search engine's extensive street mapping tool. In 2005 Google announced the addition of overhead 3D shots of cities, towns and much of the country -- known as Google Earth. However, while some of these images involved satellite technology, others relied on more traditional aerial photography using planes or helicopters, according to Google Earth software engineer, Mark Aubin. Similarly, not all photos are taken at the same time. This results in slightly different images, depending on the source.
Perspective
The different angles and sources of images for Google Earth sometimes offer different perspectives. For example, a skyscraper seen from a satellite's angle looks different to one seen from a plane. That's why tall buildings tend to most obviously suffer from the Escher Effect. All of these images are effectively "stitched" together to create a composite map of cities and landscape. So when two images from different sources are placed alongside each other, the result is often the Escher effect.
Solving the Effect
As of 2010, many of the Escher effect images in Google Earth appear to have disappeared, according to technologist and marketer Chris Silver Smith -- at least in the case of popular Google Earth locations such as city centers or popular landmarks. However, the effects still persist in some other 3D mapping tools including, Bing Maps at the time of publication.
