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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PASA.Landsat image - Great Salt Desert - Iran - small and cropped.jpg
Many image processing programs (ERDAS IMAGINE®, PCI Geomatica®, ENVI®, IDRISI®, etc.)* can import a variety of image formats, including the GeoTIFF files of Landsat data. Free Multispec software that is included with the USGS lesson plan Tracking Change Over Time can be used for limited spectral analysis. To view Landsat scenes without using...
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...
1905 Topomap scan of Des Moines
Contour Shapefiles have elevation data stored in the "CONTOURELE" attribute field. To preserve elevations, map the attribute to the elevation of the surface in Civil 3D through an "Alter Properties" query. For more guidance, follow instructions provided in Web pages, such as:
Zoom of the Black Canyon City, Arizona, US Topo quadrangle.
The USGS National Geospatial Program derives contours from the 3DEP 1/3 arc-second standard Digital Elevation Model (DEM) for US Topo topographic map products. These contours are also distributed as GIS compatible vectors in 1x1 degree tiles through The National Map Download Client. Contours on adjacent US Topo products usually match within 1:24,...
Updated 2015 version of the Madison West US Topo quadrangle
The contour visualization service, Contours (MapServer), will work as WMS or KML. At the top of the page, there are WMS GetCapabilities and Google Earthlinks. For more WMS and KML tips on services or future changes, please review the FAQ category Using TNM Services.
Photo of Santa Fe, New Mexico 2013 United States Topo map
Contours with an elevation of zero were deleted, unless there were also contours with negative elevation values in the same area. This additional processing was done for cosmetic reasons as some of the 3DEP elevation data were not of sufficient quality in coastal areas to facilitate making a satisfactory zero elevation contour.
Part of Washington DC West US Topo quadrangle, 2015
A low-pass filter was applied, which provides the basis for obtaining smoother contours.
El Capitan Quadrangle Topographic map, 2015.
Yes, contours were integrated with hydrography, but only in large scale contours from 36K to 18K.