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On a snowy morning in early March, looking for the frontiers of digital mapmaking, I hopped into the back seat of an SUV sporting a Global Positioning System receiver on the roof. In front sat two representatives from Navteq, one of the companies that builds the street maps that you see on MapQuest. Phil Satlof, senior geographic analyst, operated a laptop computer hooked up to the GPS receiver.

Looking at the computer’s screen, I felt we’d stepped inside a video game. A flashing arrow showed our progress through the familiar grid of Washington’s streets. I watched, fascinated, as it marched down a line marked “River Road” into Montgomery County, Maryland.

Half an hour later, in the wealthy suburb of Potomac, the arrow reached the limits of its knowledge. On the screen, the road ended. But our vehicle kept moving, around three new cul-de-sacs in a barren landscape of newly graded dirt, monstrous half-built houses, and yawning holes waiting for foundations. As we drove, the flashing arrow traced our route, expanding Navteq’s map of the navigable universe. Satlof added, by hand, what the GPS receiver couldn’t see: house numbers, one-way streets, and anything else that pizza delivery drivers may need to know. “We’re really a routing company, and as a by-product, we make a map,” he explained.

A few hours later and a few miles away, Apollo Teng, manager of Montgomery County’s office for geographic information systems, sat down at his computer and retrieved his own map of the area we’d just visited. I saw, once again, those three cul-de-sacs, stretching like fingers toward the Potomac River. Another click of the mouse, and we saw an aerial photograph of the scene, precisely aligned with the street map. Then property lines appeared on the map, as if by magic. When Teng clicked on a property, up came information about its owner, its tax assessment, and its most recent sale. Teng added other features: paths of sewer pipes; areas of protected wetlands; a boundary between watersheds.

Teng’s database contains more than a hundred different “layers” of information that he can add to the digital map, each layer showing different aspects of the landscape. Any piece of information that comes attached to a street address or latitude-longitude coördinates can slide effortlessly into this visualization: a neighborhood’s median income, its history of robberies, even its residents’ contributions to political campaigns.

Welcome to the astonishing world of modern mapmaking – what insiders call geographic information systems, or GIS. In fact, it’s more than mapmaking. It’s a way of organizing information about anything that happens at a particular geographic location. That includes real-estate development, military operations, logging, farming, oil drilling – the list goes on and on. GIS lets companies use mailing addresses to build maps of their customer bases, environmentalists study the effects of climate change on vegetation and glacier movement, and medical researchers investigate links between contaminated drinking water and cancer incidence. Some devotees of the technology say that it’s more than just a useful tool. They call it a new language, one that allows us to understand, and improve, our planet.


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