Frequently Asked Questions

Mapping, Remote Sensing, and Geospatial Data

The USGS provides the mapping and digital geospatial foundation for the Nation.

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Image shows a satellite view of wildfire damage in Argentina
A custom color stretch is performed on the images, based on individual scene content. Scenes from within the same area and/or acquisition date might vary in band content (due to differences such as cloud content or ground moisture). This differing content will cause variation in the results of the color stretch.   Pixelation is an artifact of the...
Chesapeake Bay 2014 Landsat imagery
Landsat scenes directly downlinked to the USGS EROS Landsat Ground Station become available through EarthExplorer within 6 hours after acquisition, and then become visible in GloVis and the LandsatLook Viewer within 24 hours. Scenes downlinked to other USGS Ground Stations can be available within 1 to 2 weeks. Scenes downlinked to International...
Kaskawulsh Glacier, Yukon Territory, Canada, Landsat 8, taken July 4, 2016
There are no restrictions on Landsat data downloaded from the USGS; it can be used or redistributed as desired. We do request that you include a statement of the data source when citing, copying, or reprinting USGS Landsat data or images. Details are on the EROS Data Citation page. Learn more: USGS Copyrights and Credits statement  
Landsat Imagery
The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey. On July 23, 1972, in cooperation with NASA, the Earth Resources Technology Satellite (ERTS-1) was launched. It was later renamed Landsat 1. Additional Landsat satellites followed in the 1970s and 1980s. Landsat 7 was...
The Bumble Bee, Arizona US Topo map
Yes, depression contours are identified with tick marks, but only in large scale contours from 36K to 18K.
Improved Topo Base map of the Glacier Peak WA area
The 500-foot contours are shown at a scale of 578K in base maps, while 100-foot contours are visible at 289K/144K and 50-foot contours are visible at 72K.  Large scale contours from US Topo products are shown from 36K to 18K, and in dynamic base map services for scales larger than 18K.
Lookout Mountain and the Tennessee River, Chattanooga, TN
Contours cover the conterminous United States at small (578K/289K), medium (144K/72K), and large (36K/18K) scales.
AK Mount McKinley A-3 US Topo (Browse Image for Story Map)
When significant changes in the landscape have occurred, contours will be updated on an as-needed basis.   The 100-foot contours were derived from 3DEP (formerly National Elevation Dataset) one arc-second resolution data that was sub-sampled to a cell size of three arc-second. The 50-foot contours were also derived from one arc-second data. Large-...
Alaska Topographic Map Contours on Glacier
Contours are not projected, but are provided in geographic coordinates (latitude and longitude) in units of decimal degrees, and horizontally referenced to the North American Datum of 1983. Contour elevation values are vertically referenced to the North American Vertical Datum of 1988. Contours are staged in Esri File Geodatabase 10.1 or Shapefile...
 A 3DEP Image of Alaska's Denali Mountain
Updated digital elevation model (DEM) dataset files are now given a name that includes information about the resolution and format of the data. This prevents users from accidentally overwriting existing data that might have different resolutions and formats.   For example:      an older file: n44w071.zip        would now have the name: ...
WI LaCrosse Shaded Relief US Topo (Browse Image for Story Map)
The USGS plans to have high-quality lidar and IfSAR (for Alaska) coverage for all of the United States and its territories. As data becomes available, legacy Digital Elevation Models (DEMs) are being systematically replaced with new, high-resolution DEMs produced almost entirely from the lidar and ifsar data.   Sources that were used to produce...
Mercator the Man
The projection used for all tiled base map services in The National Map is the World Geodetic System 1984 (WGS 84) Web Mercator (Auxiliary Sphere) so that base map services can be used in combination with other common viewers. See Spatial Reference SR-ORG:6928 and Spatial Reference SR-ORG:7483. Dynamic overlay services are in WGS84 (see Spatial...