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.

The Power of Pictures
The most vocal advocate of the benefits of GIS is also the world’s leading seller of GIS software and services: Jack Dangermond, founder and coöwner of a Redlands, CA, company called the Environmental Systems Research Institute (ESRI). (Its motto: “Better decisions through modeling and mapping our world.”) Every summer, Dangermond presides over the ESRI User Conference, an international geography jamboree that brings together thousands of digital mapmakers from around the world. ESRI publishes some of the finest work displayed at the conference in a glossy “map book,” released annually. In recent years, these books have borne such high-minded titles as Sustaining Our World and Serving Our World.

This grandiose vision comes from Dangermond himself. “Our science is making a better world for human existence and economic development and arguably could be something that counterbalances everything negative about globalization,” he says.

The power of GIS, Dangermond argues, is that it lets us witness the world, from deforestation in the Amazon to crime in local neighborhoods. And having seen what’s happening, we can imagine changing it. GIS, Dangermond believes, “will allow us to create a better future.”

According to many, digital mapmakers have had an idealistic streak from the beginning. The most comprehensive volume on GIS, The History of Geographic Information Systems, opens with an essay by landscape architect Ian McHarg, who advocated “transparent-overlay maps” in the 1960s as a way for planners to see more clearly the aspects of nature – forests, wildlife, and marshes – that new roads and buildings would obliterate.

Those physical overlay maps inspired a generation of environmentalists, including Dangermond, who studied landscape architecture at Harvard University. The idea of creating maps from layers of data became the heart of GIS, and it’s the secret of its power. Using software like Dangermond’s, people could combine census information, satellite photos, and many other types of data to reveal relationships that were never obvious before.

At first glance, the value of GIS seems self-evident. It’s hard to imagine a more innocent and enlightening technology than a map. Maps reveal the truth about our world, and the truth, as the saying goes, will set us free. Or will it?

Nazis, Soviets, and Software
I slide a copy of The History of Geographic Information Systems across the table toward historian John Cloud, and he recoils as if it were something toxic. “The enemy,” he mutters with a twisted smile, only partly joking.

Cloud considers this book a “cover story,” a misleading history that gives university-based scientists more credit for GIS than they deserve. The real roots of digital mapping, he says, reach back to the Cold War and to the U.S. Defense Department’s secret campaign to assemble accurate maps of nuclear targets in the Soviet Union.

Before taking his current job as a historian for the National Oceanic and Atmospheric Administration, Cloud spent more than a decade assembling an alternative genealogy of GIS, showing military planners, not idealistic landscape architects, to be its fathers. In the 1950s, the Defense Department recruited scientists to determine the exact distances between the earth’s continents – essential for aiming intercontinental ballistic missiles. Later, Pentagon officials sent the first remote-sensing satellites aloft to photograph “denied territories” inside the Soviet Union. In the 1960s, the Pentagon converted those images into digital data, and in the 1980s, the U.S. Air Force launched the Global Positioning System, the essential tool for today’s mapmakers.

These military projects were the pillars on which geographic information systems were built, Cloud says. In scale and sophistication, they dwarfed anything accomplished in the civilian world at that time. And the world imagined in these maps was not one of environmental sustainability but one of nuclear war.

As for Ian McHarg’s transparent-overlay maps, intended to help preserve nature and facilitate more-livable cities – well, that, too, is a nice-sounding cover story, says Cloud. There were other forerunners of layered digital maps, he says, including some that were used for less uplifting purposes than McHarg’s.

Searching through archives and old cartography publications, Cloud found several overlay maps from the 1930s and 1940s. They were, he says, “the most complex and accomplished uses of overlays yet found.” One set, prepared by federal officials during the New Deal, depicted American cities and showed, with different translucent layers, data about problems such as high concentrations of decrepit buildings. Later maps, concealed for many years from public view, carried fateful red lines that enclosed blocks occupied mainly “by any distinct racial, national, or income group that would be considered an undesirable element if introduced into other parts of the city,” in the words of a 1936 document cited by Cloud. Thus was born the term “redlining” (say, charging residents of targeted areas more for loans or insurance). Yet Cloud has found no evidence that others adopted these innovative mapmaking techniques and applied them more widely. Apparently, they were used and then abandoned.

While interviewing Lawrence Ayers, former deputy director of the U.S. Defense Mapping Agency, Cloud learned of another set of overlay maps that may have fallen on more-fertile ground. The maps were created by the German military during World War II and captured by American forces near the end of the war. They were composed of transparent sheets – sometimes 20 or more – showing such things as vegetation, soil, and road surfaces. According to Ayers, the Defense Department’s own mapmakers quickly saw the value of this technique and adopted it themselves, first applying it to physical maps, then to digital sets of data. “The concept of the overlay is what the software writers picked up and used to take advantage of digital technology,” says Ayers. “It goes back to the Germans.”

Ayers and Cloud make an odd pair of allies. But the two of them – one a retired defense official and corporate executive, the other a sandal-wearing former academic and environmental activist – agree the Defense Department laid the foundations for what’s now called GIS. It created the earliest digital maps, and its contracts “pumped money,” as Ayers puts it, into several companies that now play leading roles in the GIS industry.

Showing the Way
Some historians and GIS pioneers, however, dismiss this version of GIS history with a mixture of irritation and disdain. Nicholas Chrisman, from Laval University in Quebec City, says the Pentagon produced little, apart from the Global Positioning System, that the commercial world ever found useful. And none of the early developers of GIS software even knew about the physical overlay maps of the New Deal or the Nazi era, he says, while they certainly did know about McHarg’s. ESRI’s Dangermond, for his part, says his company knew little about the military’s work and profited even less from it.

The Pentagon didn’t invent the entire field of GIS, as Clark implies. Yet his search for the dark, hidden ancestors of modern mapmaking illustrates something simple and true: maps – like technological progress itself – are not inherently benevolent.

Even Dangermond, when pressed, concedes the point. “I’m not political about how technology gets used. It gets used,” he says. “My own interest was obviously in the area of environmental things. But it gets used by everybody.”

The consequences of those uses vary. Six months ago, relief workers used digital maps to find their way through areas devastated by the Indian Ocean tsunami. The U.S. Air Force relies on such maps in Iraq. Aerial photographs and digital mapmaking tools are allowing the governments of Uruguay and Brazil to survey and sell off vast tracts of land. “Sitting there in Arlington, Virginia, you can buy land in Brazil,” says Christopher Simpson, a professor of communications at American University in Washington, DC, who’s been studying current uses of remote sensing in Latin America. In theory, Brazilian peasants can buy the land they currently till. But in practice, Simpson says, the best properties will be snapped up by “those with the most resources, who are best organized, with the best overview.” In other words, those with access to digital maps of millions of unclaimed acres.

Geographic information systems extend the reach of the human imagination, but in the end, they mainly help people do what they wanted to do in the first place. They’re tools for preserving nature or destroying it, for defending human communities or obliterating them, for empowering or impoverishing. Maps can show us the way, wherever we choose to go.

Daniel Charles reported on technology for National Public Radio and wrote Master Mind: The Rise and Fall of Fritz Haber, the Nobel Laureate Who Launched the Age of Chemical Warfare.