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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Example of Scan Mirror Anomaly in Landsat 7 ETM+ browse image.
A number of artifacts and anomalies can happen to any remote sensing data. Banding, dropped scan lines, and detector failures are only a few of the anomalies that can be seen in Landsat data. Go to Landsat Known Issues for details about anomalies that have been discovered and investigated.
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, which 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) datasets are now renamed with a different naming convention to include resolution and format in the file name to prevent users from accidentally overwriting existing data with the same file names across multiple resolutions and formats. For example, the file name of USGS_NED_13_n44w071_GridFloat.zip replaces...
WI LaCrosse Shaded Relief US Topo (Browse Image for Story Map)
3DEP standard DEMs are produced from the highest quality elevation sources within the data holdings of the USGS National Geospatial Program. As of 2015, about 25% of the conterminous U.S. coverage is from high resolution lidar and photogrammetric source, while the remainder of the conterminous U.S. and Hawaii coverage is from USGS topographic map...