Microsoft unveils 3-D maps of cities

Microsoft Corp. has upgraded its online mapping service to include three-dimensional tours of 15 U.S. cities, marking another step in its dogged pursuit of Internet search leader Google Inc.

With the improvements unveiled Monday, Microsoft is hoping to upstage Google’s popular “Earth” software, which enables about one-third of the world’s population to obtain an aerial view of their homes and neighborhoods.

Google says it has distributed more than 100 million free copies of the Earth software since its June 2005 introduction.

Microsoft, the world’s largest software maker, is touting its 3-D version of “Virtual Earth” as a more compelling alternative that provides “photorealistic” images of the 15 targeted cities: San Francisco, San Jose, Seattle, Boston, Philadelphia, Los Angeles, Las Vegas, Detroit, Phoenix, Houston, Baltimore, Atlanta, Denver, Dallas and Fort Worth, Texas.