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U.S. Landsat Analysis Ready Data
U.S. Landsat Analysis Ready Data (ARD) products are consistently processed to the highest scientific standards and level of processing required for direct use in monitoring and assessing landscape change. Landsat Collections Level-1 scenes serve as the input for generating all Landsat ARD products.
The U.S. Landsat Analysis Ready Data (ARD) Data Format Control Book (DFCB) provides details and specifications about the ARD data packages and products.Access Documentation
The U.S. Landsat Analysis Ready Data Tile Conversion Tool converts a single Landsat WRS-2 path / row or latitude/longitude coordinates into the corresponding Landsat ARD tile.Access ARD Tool
EarthExplorer allows users to search and download Landsat data products. The U.S. Landsat 4-8 ARD dataset is listed under the Landsat → Landsat Analysis Ready Data section on the Data Set tab.Go to EarthExplorer
Landsat ARD significantly reduces the magnitude of data processing for application scientists, who currently have to download and prepare large amounts of Landsat scene-based data for time-series investigative analysis.
U.S. Landsat ARD is available for the conterminous United States (CONUS), Alaska and Hawaii using the following Landsat Collection 1 Level-1 products:
- Landsat 8 Operational Land Imager (OLI)/ Thermal Infrared Sensor (TIRS) Tier 1, Tier 2
- Landsat 7 Enhanced Thematic Mapper Plus (ETM+) Tier 1
Landsat 4-5 Thematic Mapper (TM) Tier 1
For CONUS, ARD is available from 1982-present.*
Global Landsat ARD specifications are being developed. Information will be provided when details become available.
U.S. Landsat ARD Specifications
U.S. Landsat ARD products are generated in the Albers Equal Area (AEA) Conic map projection, processed directly from Landsat Level-1 AEA scenes through Landsat Level-2 data products using the WGS84 datum and provided in Georeferenced Tagged Image File Format (GeoTIFF).
U.S. Landsat ARD products are processed to a common tiling scheme, which is modified from the Web-Enabled Landsat Data (WELD) system developed at South Dakota State University (SDSU) (Roy and others, 2010). The WELD-defined grid is similar to the National Land Cover Dataset (NLCD), except that WELD is based on the World Geodetic System 84 (WGS84) datum and NLCD uses the North American Datum 1983 (NAD83), causing an approximately 0.5 pixel offset in the X and Y directions between the two grids.
The U.S. Landsat ARD grid is anchored to the coordinates listed below. These grid origins are defined in relation to the WGS84 datum used by WELD, but are adjusted to align with the origin used by NLCD datasets.
Each tile contains 5,000 x 5,000 30-meter pixels, and includes all the pixels acquired in a given day within its extents. The ARD tile pixel dimension (number of columns and rows) is smaller than the dimensions of individual Landsat acquisitions (Landsat 8: ~6300 x ~6000 pixels; Landsat 7: ~6,166 x ~5,666 pixels).
- 422 tiles cover the land mass extent of the conterminous United States (CONUS)
- 110 tiles cover the land mass extent of Alaska
8 tiles cover the islands of Hawaii
In the event an ARD tile intersects more than one row along a WRS-2 path, the northernmost row data will populate the tile from areas where rows overlapas, as seen in the image below. This image shows the coverage of ARD tile h05v02 (outlined in white) compared to the WRS-2 path 44 row 27 image covering an area in central Washington state. The ARD tile also includes data from rows 26 and 28. Future versions of ARD may implement a more sophisticated compositing scheme to populate the tile from row overlap areas.
The image below shows the coverage of ARD tile h05v02 (outlined in white) compared to the WRS-2 path 44 row 27 image covering an area in central Washington state. The ARD tile also includes data from rows 26 and 28. (U.S. Landsat ARD Product ID: LC08_CU_005002_20130603_20170713_C01_V01; Lansdsat 8 Scene Product ID: LC08_L1TP_044027_20130603_20170310_01_T1).
U.S. Landsat ARD Products and Packaging
U.S. Landsat ARD consists of the following products, which are gridded to a common cartographic projection, and accompanied by metadata to enable further processing for the user while also retaining the traceability of data provenance:
- Top of atmosphere (TA) reflectance (reflectance calculated 'at-sensor', not atmospherically corrected)
- Top of atmosphere brightness temperature (BT) (radiance calculated 'at-sensor', not atmospherically corrected, expressed in Kelvin)
- Surface reflectance (SR) (atmospherically corrected)
Pixel quality assessment (QA) (common and sensor-specific quality bands included)
The current definition of U.S. Landsat ARD includes the products output by the following algorithms:
- Landsat 4-5 TM and Landsat 7 ETM+: Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) Surface Reflectance Algorithm (Version 3.1.2)
- Landsat 8 OLI/TIRS: Landsat Surface Reflectance Code (LaSRC) (Version 1.2.0)
Earth Resources Observation and Science (EROS) Science Processing Architecture (ESPA) Level-2 Quality Assessment Tools: L2QA-TOOLS (Version 1.2.0)
Future ARD product additions include Surface Temperature (ST) and results from land surface change detection algorithms. Subsequently, numerous products derived from ARD that are used as direct inputs to monitoring and assessment activities are in development:
- Dynamic Surface Water Extent (DSWE)
- Fractional Snow Covered Area (fSCA)
- Burned Area (BA)
- Maps of land cover and land cover change
U.S. Landsat ARD product package and band identifiers are both derived from the Landsat ARD Product ID. While the ARD Product ID follows the naming convention of its collection-based data source to the best extent possible, the ARD Product ID replaces WRS path and row designations with tile identifiers (i.e., HHH horizontal and VVV vertical), as an ARD tile may include data from overlapping rows. Processing level (LLLL) and collection category (TX) are removed from the ARD Product ID as a redundancy; the Level-1 processing date is also removed from the ARD file name.
U.S. Landsat ARD products are packaged into bundles, i.e., TA reflectance, SR, and BT are delivered in separate files, each with their associated pixel quality assessment (QA) attributes. Files containing only QA bands are also provided.
U.S. Landsat ARD bundles are delivered as .tar files, named according to the terms and definitions noted in Section 3 of the U.S. Landsat ARD Data Format Control Book (DFCB). A comprehensive Extensible Markup Language (XML) file containing all associated metadata is delivered with each ARD package <ARD Tile XML metadata schema>.
Within each U.S. Landsat ARD Package, a GeoTIFF (.tif) file is included for each band; these terms and definitions, as well as individual band specifications and other important information about each U.S. Landsat ARD product and QA bit index values are noted in Section 3 of the U.S. Landsat ARD Data Format Control Book (DFCB).
U.S. Landsat ARD Tiles Caveats
Due to the structure of the U.S. Landsat ARD grid compared to the traditional Landsat path/row designations, users are encouraged to study their areas of interest to determine which tile(s) are best suited for their scientific application.
For some tiles, there may not be sufficient data to fill the tile, depending on where the path/row scene is located within the tile. The images below represent the image data and fill amounts that can be found in sample tile h26v08 in Western Pennsylvania. From left to right: Landsat 8, May 11, 2015; Landsat 4 TM, November 25, 1982; Landsat 8, July 2, 2014; and Landsat 5 TM, March 7, 2009.
U.S. Landsat ARD Known Artifacts
Interesting artifacts have been discovered in U.S. Landsat ARD during science validation and analysis. The U.S. Landsat ARD Artifacts page describes each artifact, and as product research continues, any additional information will be added.