Closing a deal to develop a large commercial real estate project can hinge on any of a number of details. Industry insiders for years have vied to wow their clients with cool tools and glitzy presentations to put them over the top.

But now, thanks to a phalanx of e-commerce start-ups, small and large players alike can have equal access to cutting-edge mapping tools. Using these applications, which more often than not are web-based, real estate players can show their clients aerial photos of the property in question, as well as a host of other details.

The latest player to enter the market is Keyhole Corp., a technology start-up launching its EarthViewer service later this month. With EarthViewer, users can "fly" down to a location using satellite and aerial photos.

"It can easily cost $30,000 to $50,000 for real estate firms to try and develop an aerial photo exploitation program in-house," said John Hanke, CEO for Keyhole. "Even some larger real estate entities shy away from it."

EarthViewer integrates street maps into its application, allowing street names and other information to be overlaid directly onto the photos. Real estate brokers can show clients not only an aerial view of the neighborhood, but also nearby restaurants and businesses. The EarthViewer database currently includes 4.6 million identifiable businesses.

"A Realtor sitting at his desk can fly around the area of Los Angeles or Chicago as though they are in a helicopter," Hanke said. "It's a great way to understand properties, as well as see how close they are to amenities, restaurants and other business infrastructure."

The 3-D photos reveal great detail, including close-ups of structures. Users can see objects as small as cars and people.

"The quality of data varies from city to city and neighborhood to neighborhood," Hanke said. "The best resolution we have has each pixel on the screen equal to 6 inches."

When Keyhole launches its service, EarthViewer will include 40 U.S. cities. Image data will be updated annually. Some markets with fast-growing outlying areas may be refreshed more often, Hanke added.

Keyhole and its competitors gather data from firms including satellite providers, aerial photo businesses and other companies typically tapped by commercial real estate companies for similar data. The photos then can be accessed over the Internet via a subscription service. Some companies also offer on-site installations for real estate firms.

Keyhole also plans to allow its imagery to be loaded onto handheld devices like PDAs and pocket PCs.

Keyhole competitor Skyline Software Systems has offered similar applications since 1997. The company's Digital Earth application can be accessed via the Internet for a subscription-based price. Like Keyhole, Skyline offers maps. But these maps are side-by-side with satellite imagery, rather than being transposed onto photographs.

A newer competitor, GlobeXplorer, was founded in 1999. The company claims to maintain the world's largest commercial collection of aerial images. It offers access to these images through the Web, as well as on CD-ROM. The company has partnered with MapQuest to offer maps side-by-side with its images.

GlobeXplorer also offers an online demo where users can see aerial images of cool landmarks, from the Tower of London to the Grand Canyon.

Pricing for all of these services varies widely based on the number of users. Companies can expect to pay a few thousand dollars for a year-long site subscription. Keyhole has yet to price its services.

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