Washington — In 1883, John Wesley Powell, a Civil War veteran with a shovel-shaped beard and a thirst for exploration, set out to map every hill, hamlet, waterway, and wood in the United States.
Mr. Powell, then head of the US Geological Survey, promised Congress that his government-funded effort to measure the country in minute detail would take 24 years. But the vastness of the American continent has had a way of interfering with men's plans. A century after Powell began it, the National Mapping Program - the official, baseline record of US topography - still isn't finished.
So far, about 82 percent of the country has been mapped in large scale by the US Geological Survey. USGS officials say they'll be done with the task around the end of this decade.
''We have this saying around here,'' says Roy Mullen, associate chief of the Geological Survey's mapping division. ''Only a country as rich as ours can afford to be so poorly mapped.''
If it wasn't for Powell, the USGS effort to produce a comprehensive, highly accurate picture of the face of the US would undoubtedly be even further from completion than it is.
A self-taught scientist made famous by his pioneering trips down the Colorado River, Powell helped found the US Geological Survey in 1879. He was the first government official to see that the fast-growing country needed a comprehensive series of topographic base maps to help plan economic development.
Thus was born the National Mapping Program. The program, originally a plan simply to map the country once at a scale of about one mile of ground to one inch of map, has over the years been significantly expanded - a major reason why it isn't finished.
The base maps' scale is now one inch to 2,000 feet of ground, twice as detailed as in Powell's time. And these are not the sort of charts that used to be given away free at gas stations. The maps are beautiful, six-color sheets that use fine contour lines to depict mountains, ridges, valleys, and plateaus.
So far, USGS cartographers have completely mapped only 15 states at this detailed scale. Parts of many other states have also been mapped. They have 18 percent of the surface of the US to go.
''Generally, it is underdeveloped areas, mostly in the West, that aren't covered,'' says Mr. Mullen of the USGS. ''The two major areas not done are the Sierra Nevada/Cascade mountains, and upper Maine.''
In one sense the National Mapping Program will never be done. While the USGS scribbles away at new maps, old ones are made obsolete by man-made changes such as expansion of cities. Seven thousand maps need to be retouched every year, Mr. Mullen estimates, but USGS only has the resources to revise 1,200 annually.
In Europe, where countries are smaller and land rights subsequently loom larger than in the US, mapping is a high government priority, says Muller. Britain's mapping agency has about 4,000 employees, he says, while the USGS today employs 1,850 people to survey US geology and produce maps in a variety of scales and styles.
Almost all USGS mapping is now photogrammetric - produced by using aerial photographs and stereoscopic plotting instruments.
The process works like this: A pair of pictures covering approximately the same ground, but shot from different angles, is mounted in a machine that appears to be a giant metal spider with binoculars for eyes.
The machine, a stereoscopic plotter, is a sophisticated relative of the small , 3-D viewers available at many tourist gift shops.
A technician, peering through the plotter binoculars, sees a three-dimensional image of the ground. With the help of a mechanical drafting device, he traces the land contours, outlines cities and forests, and marks off roads. This map manuscript is later polished into a final product.
Before the advent of photomapping, around the end of World War II, mapmaking was a far more laborious process involving days of surveying in the field. Today , with the advent of powerful computers, mapping may be on the verge of another labor-saving technological breakthrough.
The USGS has two new map-drawing computers that - put in its simplest terms - can do much of the plotter technician's work. So far, the computer is doing fine at determining elevations, says Muller, but has a hard time at such seemingly simple tasks as distinguishing between a road and a river.
Right now, about 5 percent of USGS maps are produced digitally from a computer data base, says Mullen. By the 1990s, he predicts, 95 percent of USGS cartography will be computerized.