How accurate are US Topo maps, and why don't they have an accuracy statement?
US Topo maps are as accurate as the data sources used to make them, but because these sources are many and varied, it is not possible to make a single simple statement that the map as a whole meets a particular level of accuracy. US Topo maps, therefore, do not have a traditional accuracy statement in the map collar. Accuracy information for individual data sources is included in the metadata file that’s attached to each US Topo’s GeoPDF file (open the file in Acrobat Reader and click on the paperclip icon) and each GeoTIFF file.
There are reasons to believe that the overall accuracy of the US Topo series is very good. High-accuracy geospatial data is increasingly common, mostly due to Global Positioning System (GPS) technology. The orthoimage layer in US Topo maps is derived from images of the National Agriculture Imagery Program (NAIP). 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.
Regardless of actual accuracy, USGS maps and geospatial products are intended for general reference and are not authoritative or official for navigation or for any regulatory purpose.
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Why don't the elevations on your maps agree with those provided by my GPS system? Which are correct? Why don't the elevations on your maps agree with those provided by my GPS system? Which are correct?
Elevations provided by your GPS receiver might disagree with elevations on a USGS map, but they could both be correct if they reference different vertical and/or horizontal datums. The default horizontal datum setting on most GPS receivers is the World Geodetic System of 1984 (WGS84) and the elevations are based on the NAD83 ellipsoid. USGS topographic maps published after 2009 are georeferenced...
Why don’t the boundaries on US Topo maps match and why are some missing? Why don’t the boundaries on US Topo maps match and why are some missing?
Improving boundaries for USGS topographic maps is an ongoing effort. Boundaries have been added to computer-generated US Topo maps (published 2009-present) as digital versions become available: 2009-2010 – The U.S. national boundary was the only boundary shown. 2011 – State and county boundaries added using TIGER/Line data from the U.S. Census Bureau. 2011 – U.S. Forest Service areas added. 2013...
Related
Why don't the elevations on your maps agree with those provided by my GPS system? Which are correct? Why don't the elevations on your maps agree with those provided by my GPS system? Which are correct?
Elevations provided by your GPS receiver might disagree with elevations on a USGS map, but they could both be correct if they reference different vertical and/or horizontal datums. The default horizontal datum setting on most GPS receivers is the World Geodetic System of 1984 (WGS84) and the elevations are based on the NAD83 ellipsoid. USGS topographic maps published after 2009 are georeferenced...
Why don’t the boundaries on US Topo maps match and why are some missing? Why don’t the boundaries on US Topo maps match and why are some missing?
Improving boundaries for USGS topographic maps is an ongoing effort. Boundaries have been added to computer-generated US Topo maps (published 2009-present) as digital versions become available: 2009-2010 – The U.S. national boundary was the only boundary shown. 2011 – State and county boundaries added using TIGER/Line data from the U.S. Census Bureau. 2011 – U.S. Forest Service areas added. 2013...