To capture the images to create the panoramic views, Microsoft researchers mount a digital camera on a motorized platform on a building’s roof. The camera then slowly pans the scene, taking pictures as the camera’s view snakes in an up-and-down orientation. Cohen says that each picture takes two to three seconds to capture, adding up to about 90 minutes of picture taking. The images are then processed by Microsoft’s “stitching” software, which combines the hundreds of photos.
Traditionally, large panoramas have been created by software that automatically pieces together images, but this often blurs images, says Cohen. Additionally, most software fails to account for the changes in natural light that occur over the hour-long photo shoots.
Microsoft’s software tackles these problems by using algorithms that scour each individual picture for signature features – lines at the top of the building or bright points such as sunlight reflected in windows – and aligns them. Then, Uyttendaele says, the software “cuts” the images, as opposed to “blurring” them, which is how most panoramic software inelegantly stitches images together. Cutting is often needed for images of roads; for example, if there are two pictures of a road, with a car in one picture but not the other, the software will “cut” the portion of the picture with the car, instead of averaging or “blurring” the two images together. “This avoids ‘ghosts’ when objects such as cars are moving,” Cohen says.
Additionally, Uyttendaele says, the software compensates for lighting changes over an hour’s time by adjusting each picture’s brightness to match the preceding one’s brightness. This process keeps a daytime sky appearing light and shadows of buildings dark consistently throughout the panorama.
Being able to incorporate the Bird’s Eye and panoramic images into online navigation is changing the map-making experience, says Robert Dollison, project manager for the U.S. Geological Survey’s Geospatial One-Stop project. Projects such as Microsoft’s Live Local and Google Earth are “driving more development in the field,” he says.
The challenge in this new type of mapmaking, Bobbit says, remains in making the mapping interface easy to use – not in how many nice photos are available. Making Live Local more user friendly is one of the goals of this research, says Microsoft’s Uyttendaele. “People love the detail of the [Bird’s Eye] imagery,” he says. “This should allow them to easily pan across the images.”
At the Microsoft Research Silicon Valley Road Show, the company demonstrated a number of prototypes designed to work with Microsoft’s online mapping application, Windows Live Local. Next week, we’ll describe another research project that makes real-time information, from traffic jams to restaurant wait times, searchable via online maps.