A Google map is no longer just a Google map.
You can still search Google Maps to figure out how to get from here to there, but why would you, when you can use it to pinpoint kosher restaurants in Cincinnati, traffic cameras in Dublin, or hot spring spas anywhere in the United States? How about finding coffee shops in Seattle that provide free wireless Internet access? Or would you prefer to locate the McMansion your boss just bought and find how out exactly how much he paid for it?
An army of programmers, most of them doing it just for fun, has grabbed the software code that generates the distinctive maps with their drop-shadowed virtual pushpins, and combined it with other data like the locations of potholes, taco trucks and U.F.O. sightings, and even the sites of murders and muggings.
The result is Google map mash-ups, the latest form of Internet information repackaged for entertainment and, perhaps, profit. For instance, type the official airline flight abbreviation and flight number into the Google search engine and FBOweb.com should come up at the top of the results page. Click on that and you will see a pushpin marking the spot where the plane is. The service also provides a data box listing the speed, altitude and estimated time of arrival of the flight.
Another service, Homepricerecords.com, combines the home sales data with a Google map when you type in an address. (It currently has data only for homes in the San Francisco and Los Angeles areas, but the service promises that Chicago and New York data are coming soon.)
No one really knows how many Google map mash-ups are out there, and it is difficult to hazard a guess on how many new ones are created each day. But that does not stop some bloggers from desperately racing to keep up with the latest. Mike Pegg, an account manager for a software company in Waterloo, Ontario, is one of them. He created Google Maps Mania (www.gmapsmania.com) several months ago in a quixotic attempt to chronicle the phenomenon.
Almost every day he lists a dozen new ones, ranging from the commonplace, like sex offender maps, to the esoteric, like bird sightings in India. "I am their press release," Mr. Pegg said.
Mash-ups are not a new phenomenon on the Web. Musicians have been doing something similar with other artists' songs for some time. The best-known example is DJ Danger Mouse's combination of the Beatles' "White Album" with Jay-Z's "Black Album" last year to yield "The Grey Album." Online, Hopstop.com combines subway and bus directions in New York, Boston and Washington with a database of restaurants and entertainment spots.
What is new is that big companies are encouraging users to tap into the information. Amazon has been allowing entrepreneurs to hijack parts of its database and software code to create new applications like MusicPlasma, which graphically displays connections between various musical artists. (Type in the band Weezer and a constellation of other bands, like Nirvana, Nine Inch Nails and Zwan, surround it). The site, recently renamed Liveplasma.com, has created a similar search tool for movies and - no surprise - has a free mapping feature for its habitués.
"It is happening so fast," said Jef Poskanzer, a longtime programmer in Berkeley, Calif., who has created a hot springs map as well as maps of old star forts in Paris, a yacht race and public transportation systems in Paris and the San Francisco Bay area. "This is like the 1990's, when everyone was creating everything on the Web."
The difference, he said, is that it is now even more democratic because it is so simple to do. "It still takes a programmer to write these kinds of Google maps, but it is easier because you can go to another site and copy the code," he said.
It just got a lot easier. A company started by Marc Andreessen, a co-founder of Netscape, hopes to democratize map mash-ups even more. He created Ning.com, which automates the tools needed to create a Google-based map so almost anyone can make one.
Once you have registered for "developer status," the site copies the code behind a particular Web site you want to imitate, allowing you tweak it and make it your own. In less than five minutes, you could have the Mung Bean Salad Restaurant site up and running.
Google recognized while developing the mapping feature that it would not have the time or the desire to create a host of special interest maps. Yet having numerous mash-ups would serve Google's strategy of becoming the ubiquitous organizer of the world's information - hence its openness. The company made it economically and technically feasible for Web sites to present data in map form, said Bret Taylor, product manager for Google Local.
Yahoo has opened the A.P.I.'s behind several of its Web services, including Flickr, its photo-storing site; Yahoo Shopping; and Yahoo Maps. Even Microsoft, which has been guarded about sharing its code, has released the A.P.I. for its mapping feature. But Google Maps caught on fastest and now seems to have the greatest number of developers writing for it. (Exactly how many, Google said, is a closely guarded secret.)
Mr. Taylor said one reason for the Google Maps' popularity may be that Google allows mash-up creators to share in the revenue from ads that Google sells and places on sites. (In fact, in exchange for allowing use of the maps, Google reserves the right to run ads on the sites in the future.) "It's great for the developer and it's great for Google," Mr. Taylor said.
A new class of entrepreneur is jumping in as well. Pete Flint, a 2004 graduate of Stanford University's business school, and a classmate, Sami Inkinen, started a mash-up called Trulia.com, which pinpoints real estate listings on a Google map. Click on a pushpin in a favorite neighborhood and up pops the listings, along with comparables from recent home sales and other nearby properties.
Trulia has posted data only for five California cities, and that data is a bit thin because it uses publicly available sources like newspapers and Web sites, not the Multiple Listing Service, the copyrighted databases belonging to local broker associations. Trulia plans on adding additional layers of information, like census data.
But it is already easy to see the income-earning possibilities, either through advertising or generating highly specific leads for real estate agents. "We very much follow the Google model," Mr. Flint said. "It is just a much more focused model of the Google search engine."
Google's openness to the use of its maps does have limits, though. Once a mash-up turns into a large-scale commercial enterprise, Google looks to share in the revenue. That is happening at Trulia; Google lawyers are trying to negotiate a royalty agreement. "At the moment it is free," Mr. Flint said, "and we are taking advantage of it."