[at-l] US Topo from USGS
rockdancer97 at comcast.net
Mon Nov 29 09:26:31 CST 2010
This is from the Charlottesville, VA Daily Progress, the PATC is quoted about use for AT hikers. --RD
USGS changing the way it makes maps
By Ted Strong
November 26, 2010
The way the federal government maps the country, including the Charlottesville area, 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. One “quad,” for example, runs from the South Fork Rivanna Reservoir and Stonefield in the north to Mill Creek and Shadwell in the south, taking in about half of Charlottesville in the process. 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 stream bed, 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. The Charlottesville area doesn’t yet include land cover information, but 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.
So far, the group has covered most, but not all, of the Charlottesville area. The city itself, for example, is not yet covered by the new maps. The gaps in coverage could by caused by a number of factors, 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.
“The collective GIS information provides responders with data as to areas prone to floods and difficulties with terrain that will be faced when involved with a wildland fire (especially topo maps),” wrote Charlottesville Fire Chief Charles Werner in an e-mail.
“When the various geospatial mapping information is utilized it truly paints a picture that enables public safety to make better decisions in the areas of planning and response. When the address is tied to land features, building data and hazardous materials storage, public safety is much more aware of information that would have otherwise been unavailable,” Werner continued. “At the end of the day, local/regional geospatial data combined with other sources such as that provided by USGS improve public safety effectiveness and responder safety.”
Werner also chairs the executive committee of the Department of Homeland Security’s SAFECOM program, which examines ways that first responders share information.
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.
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