US Topo - 30 of 29
US Topo FAQs - 29 Found
The accuracy statement printed in the margin of most 20th-century USGS topographic maps referred to absolute horizontal and vertical accuracy. This statement was tied to the National Map Accuracy Standards (NMAS). 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. The maps therefore do not carry a traditional accuracy statement on the map face. Accuracy information for individual data sources is included in the metadata file attached to each US Topo file.
There are reasons to believe the overall accuracy of the US Topo series is very good. High-accuracy geospatial data is increasingly common, due mostly to the effects of 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, and they have advertised accuracy of 6 meters (~20 feet) or better. The match between US Topo vector layers and the orthoimage layer is generally very good, evidence the maps meet traditional accuracy standards for most feature classes in most areas.
Regardless of actual accuracy, USGS maps and geospatial products are for general reference and are not authoritative or official for navigation or for any regulatory purpose.