Since 2007, Google’s Street View service has provided interactive panoramic photos that make it possible to virtually stroll down streets all over the globe. Within the next two days, Street View users will be able to click on the doorways of some restaurants and other businesses to take the experience indoors.

At the Social Loco conference in San Francisco last week, Google vice president Marissa Mayer, who leads the company’s location-based technologies, showed how the new indoor imagery will be integrated with Street View. A person can click on the doorway of a store or other location to “step inside.”

“This allows you to explore and discover new businesses,” she said. “It changes how much you can interact with a business online.” A Google spokesperson told Technology Review that thousands of interiors will become available early this week.

The panoramas are captured using the same kind of techniques used to capture street views from the roof of a moving car. A device containing multiple cameras collects many partially overlapping photographs that are later stitched together into a spherical panorama of everything visible from the point at which they were taken. Panoramas can be spun around and zoomed in on by clicking and dragging. It’s also possible to jump between different panoramas inside a space to, for example, see different rooms in a restaurant.

Google’s new feature brings it into competition with Boston startup Everyscape, which has been capturing interior panoramas since 2006. The company licenses its collection of tens of thousands of indoor “scapes” to partners such as AT&T, which uses them in its YP.com business directory (see an example), and Microsoft, which uses them for the “step inside” feature of Bing local search (see an example).

Jim Schoonmaker, Everyscape’s CEO, says indoor imagery addresses an important limitation of many local search services, including Google’s. People doing Web searches have little to lose by clicking a link, but they’re more cautious about searches for local businesses. “You don’t know if your search was successful until you put your kids in the minivan and show up at a place,” Schoonmaker says.

Indoor imagery changes that, he says, which makes it valuable to businesses as well as anyone—like Google—trying to make money by offering local search. “If you can feel like you’ve already been there, your confidence in choosing to visit a new place is higher,” Schoonmaker says. Data shows that hotels with “scapes” of their interiors sell more rooms on hotel search websites than those without.

To keep up technologically with competitors like Everyscape, Google will need to do more than just capture indoor panoramas from a wide range of places. Schoonmaker’s company is already working on adding content on top of panoramic interactive photos. “You can view it as a canvas, not an endgame,” he says. “It’s competing with a website, not a regular photo.”

Everyscape panoramas can have annotations that make it possible to call up a menu by clicking on it in the panorama, or to read reviews without exiting it.

So far, Google has given no indication that it plans to do the same. But if its indoor photography mission mirrors its outdoor one, a possible next step is to collect 3-D data using laser scanners alongside panoramic photos.

Capturing 3-D data indoors is an evolutionary step beyond simple panoramas, says Paul Smith of C3 Technologies, which is using its camera-based technology to create very detailed outdoor and indoor 3-D models. “Most panoramic images are locked to only one point of view,” he explains. “You’re locked inside a bubble spinning around based on where the photo was taken.” He says the accurate 3-D and full-color models collected by C3 let the viewer explore a place more realistically, and also opens up new possibilities for indoor navigation and mobile devices.