By Ted Strong, The Daily progress, link to original post
The way the federal government maps the country is changing, with digital maps replacing old-standby paper maps. For decades, the standard for topographic maps has been quadrangles, the heavily-lined elevation-contour maps produced by the United States Geological Survey.
The maps — the old ones are still printed — cover small areas. Similar maps covering larger areas in less detail are also printed.
The maps include information such as land cover (green is generally forest, white is generally cleared areas), roads, railroads, dams, wetlands, individual buildings and the shape of the land itself.
The land’s shape is shown with series of concentric lines. The lines represent specific elevations above sea-level, each one like a ring in a bathtub. To the inexperienced, they look like a horrible mess of squiggles, almost psychedelic where they represent rough country. People who know how to read them can spot not just mountains, but ridges, valleys, cliffs, waterfalls and all manner of other features.
(Lines bunch together at steep slopes, almost stepping on one another for cliffs. Where they do that along a streambed, there will be a waterfall.)
The new program is called U.S. Topo (pronounced toe-poe, from topographic, the term for maps that show the shape of the earth).
Users have long been able to download PDF copies of quads. The new downloads, however, allow users to select which elements show up on the map. Users can select a satellite image overlay. The maps also show elevation data, waterways and names.
Once the lower 48 states are mapped, officials hope to go through and update the maps, adding more information layers to the maps along the way. They also give the ability to link from the federal map to a Google map. “We’re trying to make these U.S. topos everyman’s map,” said USGS spokesman Mark Newell.
The maps are created by importing existing data and combining it. Each new map takes about an hour to do, Newell said.
The agency is working with the U.S. Forest Service to get that agency’s map data technologically compatible with the USGS’, so maps containing national forests are often delayed. Other problems with data can hold up maps, as well, he said. Quads that slough over into not-yet-covered states are left until the other state is updated. And the agency is still working out what to do about areas that include classified government installations.
Still, in areas that are covered, response has been generally positive, Newell said. The maps have particularly been popular with emergency response personnel, he said. The ability to download maps to their own systems, rather than rely on a link to the outside, is one major plus, he said.
While response has been positive in emergency response circles, the man in charge of a set of maps in wide use locally is far from happy, saying that while on-demand maps made by assimilating existing data offer convenience, a complete shift in that direction risks losing the fine details and pinpoint accuracy for which the USGS is known.
Quads are already sub-par for trail use in many cases, said Thomas Kaye, the maps chairman for the Potomac Appalachian Trail Club. Some trails, such as the Appalachian Trail, are listed on such maps. But groups such as the PATC make specialty maps that show a more useful set of trails for the average hiker. Quads remain perhaps the best way to navigate across unknown country.
Kaye worries that the new maps, which can be updated simply by acquiring new sets of data, will lead to fewer features being routinely updated.
“Essentially, what you’re going to have updated is roads at the end of the day, and maybe some rivers and lakes, but it’s not going to be the USGS quads that we know and have come to trust,” he said.
