Maps and Mapping
How do I find, download, or order topographic maps?
What types of elevation datasets are available, what formats do they come in, and where can I download them?
What is a Digital Orthophoto Quadrangle (DOQ) or an orthoimage?
The USGS provides the mapping and digital geospatial foundation for the Nation.
How do I download The National Map data products?
Download or access The National Map data products via several applications and websites: The National Map Download Client – The primary site for data downloads. See the training videos (lessons 4a-4d) or click the Help link at the top of the Downloader for detailed instructions. LidarExplorer – Lidar Point Cloud data only. See where lidar is available, get a list of downloadable products, and...
Where can I get metadata for The National Map products and services?
Metadata for The National Map products and services is available through the following sources: In The National Map Viewer , click on the "Layer List" icon above the map, then click on the three dots to the right of the layer and select "Description" in the dropdown menu. Most layers in the Viewer are also available as Download s and/or Services . In The National Map Download Client , after...
What sources were used to create the Boundaries, Structures and Transportation layers in The National Map?
Boundaries: Primary sources include the U.S. Census Bureau, Bureau of Land Management (BLM), International Boundary Commission (IBC) for the Canadian boundary, and the International Boundary and Water Commission (IBWC) for the Mexican boundary. Boundaries include city, county, State, Federal lands, provinces, and territories; as well as cadastral data (where applicable), associated with Public...
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...
What is declination?
At most places on the Earth's surface, the compass doesn't point exactly toward geographic north. The deviation of the compass from true north is an angle called "declination" (or "magnetic declination"). It is a quantity that has been a nuisance to navigators for centuries, especially since it varies with both geographic location and time . It might surprise you to know that at very high...
Is there a cost for aerial photograph products?
Download medium-resolution scans (400 dpi) of aerial photography products at no charge using EarthExplorer . We are working on high-resolution scans (25 micron or 1,000 dpi) that can also be downloaded at no charge. With over 8.4 million frames of imagery in our archive, scanning will take many years to complete, but about 80% of high-resolution scans are currently available. If you can't find a...
What do the different colors in a color-infrared aerial photograph represent?
Color-infrared (CIR) aerial photography--often called "false color" photography because it renders the scene in colors not normally seen by the human eye--is widely used for interpretation of natural resources. Atmospheric haze does not interfere with the acquisition of the image. Live vegetation is almost always associated with red tones. Very intense reds indicate dense, vigorously growing...
How much area does an aerial photograph cover?
The area covered by an aerial photograph (air photo) depends on the scale of the imagery. Most air photos were taken on 9 x 9 inch film. The chart below reflects coverage for a variety of photographic scales. Scale 1 inch = feet 1 side (miles) Area (square miles) 1:12,000 1000 1.70 2.9 1:20,000 1667 2.84 8.1 1:24,000 2000 3.41 11.6 1:40,000 3333 5.68 32.3 1:58,000 4833 8.23 67.73 1:63,360 5280 9...