“The advantage of C3’s image-only scheme is that aerial LIDAR is significantly more expensive than photography, because you need powerful laser scanners,” says Zakhor. “In theory, you can cover more area for the same cost.” However, the LIDAR approach still dominates because it is more accurate, she says. “Using photos alone, you always need to manually correct errors that it makes,” says Zakhor. “The 64-million-dollar question is how much manual correction C3 needs to do.”
Smith says that C3’s technique is about “98 percent” automated, in terms of the time it takes to produce a model from a set of photos. “Our computer vision software is good enough that there is only some minor cleanup,” he says. “When your goal is to map the entire world, automation is essential to getting this done quickly and with less cost.” He claims that C3 can generate richer models than its competitors, faster.
Images of cities captured by C3 do appear richer than those in Google Earth, and Smith says the models will make mapping apps more functional as well as better-looking. “Behind every pixel is a depth map, so this is not just a dumb image of the city,” says Smith. On a C3 map, it is possible to mark an object’s exact location in space, whether it’s a restaurant entrance or 45th-story window.
C3 has also developed a version of its camera package to gather ground-level 3-D imagery and data from a car, boat, or Segway. This could enable the models to compete with Google’s Street View, which captures only images. C3 is working on taking the technology indoors to map buildings’ interiors and connect them with its outdoor models.
Smith says that augmented-reality apps allowing a phone or tablet to blend the virtual and real worlds are another potential use. “We can help pin down real-world imagery very accurately to solve the positioning problem,” he says. However, the accuracy of cell phones’ positioning systems will first have to catch up with that of C3’s maps. Cell phones using GPS can typically locate themselves to within tens of meters, not tens of centimeters.