Google and Microsoft are intensely focused on building 3-D maps of the world and adding social elements on top of their mapping services, executives said Friday at the Web 2.0 Summit.

During a panel discussion at the San Francisco conference, Erik Jorgensen, general manager of Live Search at Microsoft, said the software maker is spending "hundreds of millions of dollars" to build a 3-D replication of the world that would become the platform for data overlays to provide people with useful information on geographical locations.

Microsoft this week launched an upgrade of its Live Search service, which offers through the Virtual Earth platform 3-D imagery of nearly 200 U.S. cities and other areas covering 80% of the nation's population. As part of the upgrade, people using Live Search Maps can create and share their own 3-D models of buildings through an alliance with Dassault Systemes.

Google, on the other hand, announced on Wednesday that people can use the map-creation tools in Google Maps to make maps of recommended places to visit and share that information with other users of the services. In addition, the map creators can also publish profile pages with the contributions.

"The ability for more people to see [mapping] data and comment on and improve it over time is definitely where we are going," said Brian McClendon, engineering director of Google Earth.

A major hurdle to building 3-D global maps is the lack of imagery from many countries. In the United States, for example, Google and Microsoft obtain bird's-eye views of cities from companies that provide aerial and street-level photos of places. "We're investing a lot in markets like India and China, as well as areas you would expect, like Europe and APac [Asia, Pacific]," Jorgensen said.

Nevertheless, regions in Africa, for example, have proven nearly impossible to get imagery, other than satellite data or information from GPS devices. This has made it difficult to cover the world, creating a number of "black holes," Jorgensen said. "Maps in many of these countries just isn't there."

Panelist Bruce Radloff, chief technical officer of mapping data vendor Tele Atlas, said local laws are a major problem in getting data. Countries such as South Korea don't allow mapping companies to take geographical information out of the country without government approval. "It poses some interesting challenges for us," he said.

The panelists also discussed advertising on maps. Google and Microsoft are experimenting with advertising, but neither has found a method of presenting advertising that it's comfortable with. The ultimate goal is to provide ads that in some way bring something useful to the underlying map and avoid "becoming a pain to the user," Jorgensen said.