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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1914 USGS legacy topographic map of the Muscle Shoals, Alabama
A USGS topographic map is usually named for the most prominent feature within the bounds of the map, which is frequently a community. Most topographic maps are named for the most centrally located, well-known, and/or largest community identified on the map. If the community for which the map should be named falls on two or more maps, a directional...
Crop of Landsat 7 Path 38 Row 35, Acquired March 29, 2013
Landsat 7 ETM+ SLC-off data refers to all Landsat 7 images collected after May 31, 2003, when the Scan Line Corrector (SLC) failed. These products have data gaps, but are still useful and maintain the same radiometric and geometric corrections as data collected prior to the SLC failure. See the Landsat 7 website for information about the SLC-off...
Landsat image showing scar marks from fire in comparison to ASTER.
Data acquisition requests are not available to the public. The Landsat 8 and Landsat 7 satellites each acquire data on a continual basis in accordance with their respective Long Term Acquisitions Plans. The Landsat Acquisitions page has calendars and information about daily schedules. Learn more: Landsat 8 Long Term Acquisitions Plan Landsat 7...
Image shows aerial imagery of flooding in Louisiana, courtesy of the National Geodetic Survey
Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area. Special cameras collect remotely sensed imagesof the Earth, which help researchers "sense" things about the Earth. Some examples are: Cameras on satellites and...
Lidar image of Pittsburgh
Lidar data are available through The National Map Download Client. Click the “How To” link at the top of the viewer for detailed instructions on how to find and download data.   Light Detection and Ranging (LIDAR) is a technology similar to RADAR that can be used to create high-resolution digital elevation models (DEMs) with vertical accuracy as...
Aerial photo of Anvil Lake
Yes.  Scanning of the EROS film archives is following a plan to capture images from rolls at risk of decay from vinegar syndrome. Science requirements are also reviewed on a regular basis, but a formal, on-line schedule is not available at this time. Eventually almost all of the film currently held in the archive will be digitized.
High Resolution Orthoimagery coverage map on The National Map
Pursuant to 43 U.S.C. 1460, the U.S. Geological Survey (USGS) Earth Resources Observation and Science Center (EROS) hereby certifies that the product downloaded through our web site is an authentic reproduction of an official record of the Government that is in the legal custody of the USGS EROS.
Orthoimagery of Augusta Ga
The majority of USGS aircraft photography is used for cartographic purposes. Image distortion is minimized when photographs are acquired looking straight down or vertically.
Orthoimagery of the Maryland State House, Annapolis, Maryland
The high resolution orthophoto and the Digital Orthophoto Quadrangle (DOQ) provides the most detail. You would probably be able to identify your neighborhood. There is no guarantee that your home would be distinguishable. What you can distinguish is mostly a function of scale and resolution. Film resolution is dependant on film type, camera, lens...
Image: Comparison of Aerial Photo and LiDAR Image
A Fiducial site is a geographic location that is used as a benchmark for the long-term monitoring of processes, both natural and anthropogenic, associated with the causes and effects of global environmental change. The Global Fiducials Library (GFL) is a long-term archive of images from U.S. National Imagery Systems which represents a long-term...
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.