Chapter 29. How Map Sites Work

Need to find driving directions from Cincinnati to Seattle? Looking for Afghani restaurants in Cambridge, Massachusetts? Want to get a detailed a map of Lubbock, Texas?

All that, and more, are available on mapping sites on the Internet. There are a number of mapping websites you can visit, but the two most popular are MapQuest and Google Maps. MapQuest is the older and more established of the two, and the more targeted as well. It serves up maps and directions, but not much else. Google Maps, on the other hand, lets you also find local information on the maps you're looking at, such as nearby restaurants, museums, and more.

Although mapping sites look quite different from one another, and have different interfaces, if you take a look under the hood, they all operate relatively similarly.

Mapping sites, as a general rule, do not actually create the underlying mapping information themselves. Instead, they get that information from a commercial provider of mapping information. These providers typically sell mapping information not only to map sites, but to private businesses that need mapping information as well.

The providers regularly update the maps they sell to mapping sites in several different ways. Commonly, they hire people to actually drive the streets, and then update their maps to reflect any new construction, changes in streets and landmarks, and so on.

Map providers give more than just raw mapping information to map sites like MapQuest and Google Maps. They also provide a database that calculates the best driving directions from one point to another. The directions are based on a variety of complex algorithms, but generally they try to find the directions that take the least amount of time to drive, rather than the shortest distance between two points.

Map sites may make use of the same basic mapping databases, or similar databases, but the features they offer to visitorsand the interface they use to deliver those featuresare quite different.

MapQuest, for example, uses a simple, basic HTML interface, and concentrates on directions and maps. Google Maps, on the other hand, uses a far more interactive interface that allows visitors to more easily zoom in and zoom out, switch to a satellite view, and navigate through maps by dragging with a mouse. Google Maps does this by using a technique called AJAX. (For more details about AJAX, see the illustration "How AJAX Works" in Chapter 19, "How Markup Languages Work.")

Google also offers a tool more sophisticated than mere maps, Google Earth. Google Earth lets you "fly" to any location on earth in a virtual tour, using high-resolution photos and animations.