A missile-targeting technology is adapted to process aerial photos into 3-D city maps sharper than Google Earth's.
Pixel perfect: Using aerial photos,
image-processing software created this 3-D model of San Francisco,
accurate to 15 centimeters.
Credit: C3 Technologies
Credit: C3 Technologies
Technology originally developed to help missiles home in on targets has been adapted to create 3-D color models of cityscapes that capture the shapes of buildings to a resolution of 15 centimeters or less. Image-processing software distills the models from aerial photos captured by custom packages of multiple cameras.
The developer is C3 Technologies, a spinoff from Swedish aerospace company Saab. C3 is building a store of eye-popping 3-D models of major cities to license to others for mapping and other applications. The first customer to go public with an application is Nokia, which used the models for 20 U.S. and European cities for an upgraded version of its Ovi online and mobile mapping service released last week. "It's the start of the flying season in North America, and we're going to be very active this year," says Paul Smith, C3's chief strategy officer.
Although Google Earth shows photorealistic buildings in 3-D for many cities, many are assembled by hand, often by volunteers, using a combination of photos and other data in Google's SketchUp 3-D drawing program.
C3's models are generated with little human intervention. First, a plane equipped with a custom-designed package of professional-grade digital single-lens reflex cameras takes aerial photos. Four cameras look out along the main compass points, at oblique angles to the ground, to image buildings from the side as well as above. Additional cameras (the exact number is secret) capture overlapping images from their own carefully determined angles, producing a final set that contains all the information needed for a full 3-D rendering of a city's buildings. Machine-vision software developed by C3 compares pairs of overlapping images to gauge depth, just as our brains use stereo vision, to produce a richly detailed 3-D model.
"Unlike Google or Bing, all of our maps are 360° explorable," says Smith, "and everything, every building, every tree, every landmark, from the city center to the suburbs, is captured in 3-D—not just a few select buildings."
C3's approach has benefits relative to more established methods of modeling cityscapes in 3-D, says Avideh Zakhor, a UC Berkeley professor whose research group developed technology licensed by Google for its Google Earth and Street View projects. Conventionally, a city's 3-D geometry is captured first with an aerial laser scanner—a technique called LIDAR—and then software adds detail.