For almost as long as there has been civilization, there have been maps -- to record the boundaries of property and territories, to identify landmarks, to show the way to destinations.
Primitive maps grew in sophistication thanks to the ancient Greek invention of geometry, which made possible more accurate measurements of distances. More than 200 years before the Christian era began, Greeks had theorized that the Earth was round and estimated its size within 15 percent of current values.
In Europe's Age of Discovery -- roughly 1500 to 1800 A.D. -- the science of mapmaking advanced explosively as improvements in timekeeping and astronomy led to the development of the latitude and longitude grid system, allowing any spot in the world to be located. Explorers could determine exactly where they were on the grid as they charted new coastlines and lands.
Now, thanks to satellite photography, global information systems and advances in computer technology, cartographers -- both professional and amateur -- are entering what promises to be a new golden age of maps.
Over the last 10 years, the Internet has revolutionized access to mapping tools. Millions print maps and travel directions every day -- all swiftly generated on a half-dozen free and easy-to-access sites.
Global Positioning System units in cars use a network of stationary satellites to guide travel with astonishing precision. Handheld GPS units can locate anyone at any place on the globe, and even allow some techno-geeks to play an increasingly popular and sophisticated form of hide-and-seek.
But that is only the beginning of what is possible with the marriage of maps, computers and the Internet.
Growing numbers of cities and counties across America use satellite photography and sophisticated analytical tools to make real-time assessments of patterns of growth, development and land use.
Third World countries are using the same tools to create plans to limit the potential environmental ravages of rapid economic development and to plan growth to allow the most efficient use of limited infrastructure resources.
These new tools help track bird flu in Asia, prevent crime in Baltimore and manage potentially explosive urban development in China. They promise to multiply the effectiveness of analyses by scientists, economists and public planners.
Perhaps most exciting, the stories these new maps tell about our world are not the exclusive property of cartographers, geographers and professional planners. Their information is available on the Internet free, for all to see.
Anyone can become a sophisticated cartographer on the Web site of the National Atlas of the United States of America (www.nationalatlas.gov), which combines data on people, infrastructure and natural resources culled from 20 government agencies. Visitors can create maps tailored to their needs by clicking on "Map Maker," or use the site's "dynamic" feature -- interactive maps such as one that provides an overview of the nation's geology.
The U.S. Geological Survey updates the National Atlas site quarterly and also produces the topographic maps that provide the best up-close view of the national terrain. The topos, which used to be hard to find, are available free at www.topozone.com.
That's just the start of the revolution. NASA is producing a spectacular topographic atlas of the world using information gathered by radar on an 11-day mission in February 2000 of space shuttle Endeavour. Images from the Shuttle Radar Topography Mission can be found on the Internet at http:--photojournal.jpl.nasa.gov/mission/SRTM.
Then there is the remarkable new service provided by the most popular of search engines, Google. Its Google Earth allows visitors to sweep seamlessly from a satellite vantage point down to any location in the United States, Canada or Britain. You can soar over the landscape like a bird, tilting and rotating it at your whim.
Google Earth requires a relatively new PC and free software downloaded from the Google site. Google charges for versions with better views.
But such sightseeing is not the real revolution available from Google. It has released its map-generating software, or application programming interface (API), available at www.google.com/apis/maps/. With the Google API, a Google map can be combined with any geographically tagged information to create a new map.
Such homemade maps are so popular that they have earned their own Internet name -- mash-ups. Google map mash-ups have been used to plot the post-flood condition of neighborhoods in New Orleans, the current location of airline flights or neighborhood real estate sales data. Others chart commuter rail systems, public and private school data and even live weather cameras.
Nobody knows how many mash-ups have been created, but they are clearly proliferating at an amazing pace. A sampling of the latest can be found at www.googlemapsmania.blogspot.com.