More often than not, disagreements were sparked and then perpetuated by a lack of information. What exactly were the boundaries of a land grant? How many native Americans already lived on it? How much water did its rivers and aquifers hold? Was there gold or silver underground?

The sketchy and sometimes fantastical maps of the colonial era did little to answer these questions. Even the precise cartographic surveys of the 19th and 20th centuries could not reveal whether the dwellers of a particular lot had legal title, whether they had paid their taxes or whether they were cutting trees. Obtaining that sort of information has always required time-consuming legwork: field surveys to verify a boundary, tedious searches for public records at scattered government agencies, or costly on-site inspections by regulatory officials.

These obstacles, which are certainly not unique to the region, have made it difficult for governments to draft rational plans for developing either urban or rural lands. In the absence of sound planning based on accurate information, chaotic slums have grown up around major cities and huge tracts of forest and pasture land have been degraded because of inappropriate agricultural practices.

Ironically, misuse is still taking place at a time when our knowledge of the land is growing richer by the hour. Much of the new information is based on satellite imagery that until recently was either restricted for military purposes or simply too expensive for all but the richest governments and corporations. With the end of the Cold War, many governments have privatized most of their satellite imagery services, and the resulting companies are flooding the market with affordable, up-to-date images of virtually every part of the earth. Many of these satellites are equipped with sensors that can detect light in more than one spectrum-a capability that reveals an astonishing amount of information about the earth's surface and subsurface that could never be seen on the ground.

Another unexpected legacy of the Cold War is the Global Positioning System (GPS), a network of satellites built by the United States military to provide precise navigational bearings for missiles. Since it was commercialized early this decade, GPS has made it possible for land surveyors and even hikers to determine their location anywhere on the planet to within a meter or so-simply by holding a telephone-sized receiver. GPS has led to an explosion in low-cost precision mapping, allowing even modest municipal governments to convert old paper surveys into digital maps that can show the exact location of every streetlight, fire hydrant and sewage outlet in a city.

Finally, affordable digital maps have greatly enhanced the utility of geographical information systems (GIS), software programs that allow information from many different sources to be linked to items on a computerized map. A typical urban GIS might let users view an aerial photograph of every building in the city by simply clicking on a lot number in a digital map. The lot number can also be linked to a database of census data, zoning classifications, tax assessments, traffic patterns and crime reports related to that building's block. Armed with that kind of information, city administrators can make informed decisions about where to beef up police patrols, expand subway service, or authorize the construction of new clinics, schools or hotels, to name just a few applications.

In a rural setting, GIS software can turn an ordinary map into a trove of information about the legal status of a parcel, its geology, vegetation and water sources, and the type of agriculture that is being practiced on it. In the industrialized countries, agricultural GIS systems are being used for what is known as "precision farming." Here, data on the soil type and moisture content of individual fields is combined with information on specific crop requirements and weather updates. The resulting maps can show farmers where to plant seeds more or less densely and where to boost or hold back irrigation, pesticides and fertilizers throughout the growing season. Computer-assisted farm machinery and aircraft that are equipped with GPS receivers can then use those digital maps to place fertilizers and pesticides in precise amounts, just where they are needed. The net result is higher yields and fewer wasted resources.

Satellite imagery and GIS have been used by large petroleum and mining companies in Latin America for many years. More recently, local companies in agriculture, forestry, telecommunications, logistics and transportation have adopted GIS to increase efficiency and productivity.

But in the public sector, GIS technologies are only now beginning to have an impact. "Five years ago, these tools were just too expensive for most governments to use on a large scale," says Kevin Barthel, an IDB specialists who has helped design numerous Bank projects that apply GIS. "But with the growth in competition and the drop in computer and GPS technology prices, GIS is now cost-effective enough for most governments to apply it to concrete problems." He cautions that technology is never a cure-all, but that in the right conditions, GIS can help accelerate the process and lower the cost of solving difficult land-management tasks.

The following pages offer a small sample of the ways in which satellite imagery and GIS are being used to answer questions about the land and the people who use it.

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For more information, visit the Bank's Internet home page at www.iadb.org and type "GIS" in the search window.