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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Landsat 8 Collection 1 Quality Assessment Example
The C Function of Mask (CFMask) algorithm populates cloud, cloud confidence, cloud shadow, and snow/ice pixels in the processing of Landsat Collections Level-1 data products, with the results represented as bit-mapped values within the Landsat Collection 1 Level-1 Quality Assessment (QA) Band.  CFMask derives from the Function of Mask (FMask), an...
Landsat 7 100,000th orbit image
The Landsat Collection 1 Level-1 product metadata (MTL.txt) file includes a SATURATION_BAND_ x”parameter for each Landsat band. This field indicates the presence of radiometric saturation for each bandin every Landsat scene. Learn more: Landsat Collections Level-1 Saturation Bits Parameter 
Zenith and Azimuth Angles Associated with Solar Angle Bands
The Landsat Collection 1 Angle Coefficient file provides sensor viewing angle model coefficients that can be used to create angle bands, and allows users to compute the solar and sensor viewing angles on a per-pixel basis. Learn more: Solar Illumination and Sensor Viewing Angle Coefficient Files 
Crop of Landsat 7 Path 38 Row 31, Acquired March 29, 2013
The Landsat 7 SLC-off artifact does not change how the data are placed into Landsat Collection tiers, as tier classifications are determined by the radiometric and geometric accuracy of each scene. Learn more: Landsat Collections Landsat Data Access
Lenticular clouds over hills in New Zealand.
Landsat Level-1 data can be rescaled to the top of atmosphere (TOA) reflectance and/or radiance using radiometric rescaling coefficients provided in the metadata file (MTL.txt) that is delivered with the Landsat Level-1 product. The MTL file also contains the thermal constants needed to convert thermal band data to TOA brightness temperature (BT...
Earth As Art image of Kazakhstan
The historical Landsat Level-1 Scene ID is in the EarthExplorer metadata. After entering a search using the historical Scene ID, the Landsat Level-1 Collection 1 Product Identifier will be returned in the search results. The results can be exported from EarthExplorer in a variety of formats for metadata parsing. We also encourage use of the Bulk...
Earth As Art image Terkezi Oasis
The USGS archive contains data acquired by the Landsat satellites from 1972 to present. Data is downlinked to various ground stations around the world. While each ground station in the International Cooperator (IC) network is the primary source for distributing the captured data in their area, copies of the data have also been made available to...
Landsat image of the south end of San Francisco Bay Estuary and associated wetlands
Landsat descending (daytime) acquisitions run from north to south; they cross the equator between 10:00 am and 10:25 am local time on each pass to provide maximum illumination. The exact acquisition start and stop times for each scene are listed in the metadata file that is included in the Landsat Level-1 product, and also displayed on...
Landsat 7 Path 38 Row 31, Acquired March 29, 2013
The Landsat 7 and Landsat 8 satellites orbit the Earth at an altitude of 705 kilometers (438 miles) in a 185-kilometer (115-mile) swath, moving from north to south over the sunlit side of the Earth in a sun synchronous orbit, following the World Reference System (WRS-2). Each satellite makes a complete orbit every 99 minutes, completes about 14...
Earth as Art - Landsat 8
Ascending (nighttime) WRS-2 Path/Row numbers are different from descending (daytime) Path/Rows. Cloud cover values for Landsat night scenes will always be zero. If you know the daytime path/row or coordinates and want to know the nighttime path/row, use the WRS-2 Path/Row to Latitude/Longitude Converter. Use EarthExplorer to search using path/row...
Satellite image showing a picture of northeastern Alaska.
The Landsat Collection 1 Level-1 product identifier includes the Collection processing levels, processing date, collection number, and collection iter category: LXSS_LLLL_PPPRRR_YYYYMMDD_yyyymmdd_CC_TX Where: L = Landsat X = Sensor (“C”=OLI/TIRS combined, “O”=OLI-only, “T”=TIRS-only, “E”=ETM+, “T”=“TM, “M”=MSS) SS = Satellite (”07”=Landsat 7, “08...
Landsat 7 ETM+ Surface Reflectance
Landsat Collection 1 Level-1 data are not corrected for atmospheric conditions, however Landsat Science Products, which include Level-2 Surface Reflectance and Provisional Surface Temperature, and Level-3 Burned Area, Dynamic Surface Water Extent, and Fractional Snow Covered Area are atmospherically corrected. Learn more: Landsat Collections...