Google's Google Earth, Microsoft Virtual Earth, and Yahoo!'s Yahoo! Maps are compared killer maps. The companies are all converting online mapping into a full-functioned browser function with information organized according to geography in a way that will please users. For example, Google's tools are a boon for vacation planners, who can use Google Earth to search for an attraction and use the central window of Google Earth to zoom from an orbital view of North America down to a satellite image of a the location of the attraction. Clicking on a listing in the search results pops up a balloon over the image to indicate the specific attraction with street address, Web address, and a link to driving directions. MSN Virtual Earth offers satellite photos, zooming and panning, and interactive search listings that are like Google Earth's. However, Virtual Earth could serve a larger audience, because MSN Virtual Earth runs inside a browser window instead of having to be downloaded as a separate application. Yahoo! has also introduced maps that provide such locations as Wi-Fi hot spots in a specific neighborhood. Each company has released application programming interfaces (APIs) for external programmers that can be used to build online services that use a company's own map programs. Many topics are covered, including new features for users of smartphones and wireless personal digital assistants (PDAs), challenges facing wide use of location-finding technologies, and a brief history of global positioning system (GPS) technology.