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How accurate are USGS maps?
Turns out, USGS topo maps use the National Map Accuracy Standards. This means that 90 percent of the horizontal points tested by field survey teams are accurate to within 40 feet. Vertical points, to within half a contour line, or five feet, based on standard 7.5 minute, 10-foot contour lines. So, yeah.
How accurate are USGS topo maps?
The production of these images is well controlled; they have an accuracy of 6 meters (~20 feet) or better. The match between US Topo vector layers and the orthoimage layer is generally very good, evidence that the maps meet traditional accuracy standards for most feature classes in most areas.
What does Black represent on a topographic map?
The colors of the lines usually indicate similar classes of information: topographic contours (brown); lakes, streams, irrigation ditches, and other hydrographic features (blue); land grids and important roads (red); and other roads and trails, railroads, boundaries, and other cultural features (black).
What is the positional accuracy of the topo map at the 90% confidence level?
As applied to the USGS 7.5-minute quadrangle topographic map, the hori- zontal accuracy standard requires that the positions of 90 percent of all points tested must be accurate within 1/50th of an inch (0.05 centimeters) on the map.
How accurate is Google Earth topography?
The GDEM data are the most widely covered elevation data source (from 83°N to 83°S, covering about 99% the globe) with a grid resolution of 30 meters. A vertical accuracy study found the root mean square error (RMSE) of GDEM data is 8.68 meters when compared against 18,000 geodetic control points in the USA [14].
What do the lines mean on a topographic map?
Put simply, contour lines mark points of equal elevation on a map. Topographic maps use a combination of colors, shading and contour lines to represent changes in elevation and terrain shape. Essentially, topographic maps represent the three-dimensional landscape of Earth within the two-dimensional space of a map.
How often are USGS topographic maps updated?
US Topo maps are updated on a three-year production cycle (maps covering one third of the country are updated each year).
What does USGS mean?
The USGS (United States Geological Survey) is a science bureau within the United States Department of the Interior.
What is the USGS topographic map scale?
The phrase “USGS topographic map” can refer to maps with a wide range of scales, but the scale used for all modern USGS topographic maps is 1:24,000.
What does the USGS (United States Geological Survey) do?
What does the USGS (United States Geological Survey) do? The USGS (United States Geological Survey) is a science bureau within the United States Department of the Interior.
What is the USGS National Geospatial program?
The U.S. Geological Survey (USGS) National Geospatial Program is scanning published USGS 1:250,000-scale and larger topographic maps printed between 1884, the inception of the topographic mapping program, and 2006.