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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SLC-Off showing showing satellite image with parallel bands of missing image; and SLC-On gap mask with correlating blue bands.
Band-specific gap mask files are included with every Landsat 7 Scan Line Corrector (SLC)-off Level-1 data product. These ancillary data identify the location of all pixels affected by the original data gaps in the primary SLC-off scene. The gap mask is provided as a series of individual band files, in compressed (GZIP) GeoTIFF format. Left:...
Example of striping in Landsat 7 ETM+ Band 6 high gain data, processed before Nov. 23, 1999.
Landsat 7 acquires thermal data in two bands from one detector in  both high (Band 6H) and low (Band 6L) gain. The difference in gain settings is important to different types of studies (i.e., clouds vs. deserts). Aside from the resolution differences and saturation on the high and low ends, the two bands provide the same Digital Numbers (DN) for...
World Reference System-2 (WRS-2) - Day/Descending
The Worldwide Reference System (WRS) is a global system that catalogs Landsat data by Path and Row numbers. Landsat satellites 1, 2 and 3 followed WRS-1, and Landsat satellites 4,5,7, and 8 follow WRS-2. Learn more: Landsat Path Row Shapefiles and KML Files The Worldwide Reference System (NASA)
Landsat Level-2 Surface Reflectance Example
There are several Landsat data products that are useful for science applications and land use/land change studies: Landsat Collections Level 1 - Ensures that the data in the Landsat Level-1 archive are consistent in processing and data quality to support time-series analyses and data stacking. Each Level-1 data product includes individual spectral...
Geometric Desert - Earth As Art image of Egypt
Landsat Definitive Ephemeris (DE) is used for geometrically correcting Landsat 5 and Landsat 7 data. Learn more (and download DE files): Landsat Definitive Ephemeris
Aug 2013 Response Linearization Look Up Tables Update Close up - Band 6
Landsat Response Linearization Look Up Tables (RLUT) are additional files that accompany Calibration Parameter Files (CPFs) and contain a mapping lookup table to linearize the output of the Landsat 8 Operational Land Imager (OLI) detectors. Learn more (and download RLUT files): Landsat Response Linearization Look Up Tables
White Sands Radiometric Calibration Site
Landsat Bias Parameter Files (BPFs) supply radiometric correction parameters that are applied during Level-1 processing of Landsat data. Learn more (and search for BPF files): Landsat Bias Parameter 
Calibration/Validation Test Sites
Landsat Calibration Parameter Files (CPFs) provide radiometric and geometric coefficients needed for processing of raw, uncorrected Landsat image data into Level-1 data products. Over 15,000 coefficients are issued to span distinct timeframes and are updated with improved calibration coefficients. CPFs are often updated with improved coefficients...
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...
Zenith and Azimuth Angles Associated with Solar Angle Bands
The 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 35, 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 Download Landsat data using EarthExplorer, GloVis, or the LandsatLook Viewer
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...