U.S. Landsat Analysis Ready Data (ARD) are consistently processed to the highest scientific standards and level of processing required for direct use in monitoring and assessing landscape change. A fundamental goal for Landsat ARD is to significantly reduce 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.
Landsat Collections Level-1 scenes serve as the input for generating all Landsat ARD products.
U.S. Landsat ARD are 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 are available from 1982-present. The histograms below display the available Landsat Collection 1 Level-1 products used for ARD products, for Alaska and Hawaii.
|Figure 1. Landsat ARD Input Availability: Alaska||Figure 2. Landsat ARD Input Availability: Hawaii|
Global Landsat ARD specifications are being developed. Information will be provided when details become available.
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. Table 1 lists the U.S. Landsat ARD projection parameters.
Projection: Albers Equal Area Conic
Datum: World Geodetic System 84 (WGS84)
Output Format: Georeferenced Tagged Image File Format (GeoTIFF)
Table 1. U.S. Landsat Analysis Ready Data (ARD) Projection Parameters
Tile Grid System
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 in Table 2 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). (Figure 3).
- 110 tiles cover the land mass extent of Alaska (Figure 4).
8 tiles cover the islands of Hawaii (Figure 5).
Figure 3. U.S. Landsat ARD Tile Map of CONUS
Click map to view larger image, or download .pdf.
|Figure 4. U.S. Landsat ARD Tile Map of Alaska
Click map to view larger image, or download .pdf.
|Figure 5. U.S. Landsat ARD Tile Map of Hawaii
Click map to view larger image, or download .pdf.
Table 2 displays the coordinates that anchor the U.S. Landsat ARD tile grid. Refer to the U.S. Landsat ARD Data Format Control Book (DFCB) for further information.
U.S. Landsat Analysis Ready Data (ARD) Tile Grid Extents
|Upper Left Tile (ul corner)||Lower Right Tile (lr corner)|
|(h)||(v)||ulX (m)||ulY (m)||(h)||(v)||lrX (m)||lrY (m)|
Table 2. U.S. Landsat Analysis Ready Data (ARD) Tile Grid Extents
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 overlap, as seen in Figure 6 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. Subsequent versions of ARD may implement a more sophisticated compositing scheme to populate the tile from row overlap areas.
Figure 6. U.S. Landsat Analysis Ready Data (ARD) tile h05v02 overlay on Landsat 8 WRS-2 path 44 row 27
Landsat ARD Product ID: LC08_CU_005002_20130603_20170713_C01_V01
Lansdsat Scene Product ID: LC08_L1TP_044027_20130603_20170310_01_T1
U.S. Landsat ARD consist 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)
- Provisional Surface Temperature (ST)
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 will include results from land surface change detection algorithms. Numerous products derived from ARD useful as direct inputs to monitoring and assessment activities are in development:
- Maps of land cover and land cover change
- Burned Area (Coming soon in 2018)
- Dynamic Surface Water Extent (Coming soon in 2018)
Fractional Snow Covered Area (Coming soon in 2018)
Packaging and Filenames
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 Packages are delivered as .tar files, named according to the terms and definitions shown below. A comprehensive Extensible Markup Language (XML) file containing all associated metadata is delivered with each ARD package. <ARD Tile XML metadata schema>.
Refer to Section 3 of the U.S. Landsat ARD Data Format Control Book (DFCB) for a listing of files included for each product package.
U.S. Landsat Analysis Ready Data (ARD) Package Terms and Definitions
|X||Sensor (“T” = TM, “E” = ETM+, “C” = OLI/TIRS Combined, “O” = OLI-only, “T” = TIRS-only)|
|SS||Satellite (“04” = Landsat 4, “05” = Landsat 5, “07” = Landsat 7, “08” = Landsat 8)|
|US||Regional grid of the U.S. (“CU” = CONUS, “AK” = Alaska, “HI” = Hawaii)|
|HHH||Horizontal tile number|
|VVV||Vertical tile number|
|YYYYMMDD||Acquisition year (YYYY) month (MM) day (DD)|
|yyyymmdd||Production year (yyyy) month (mm) day (dd)|
|CCC||Level-1 Collection number (“C01,” “C02”)|
|VVV||ARD Version number (“V01,” “V02”)|
|PRODUCT||Data product (“TA” = top of atmosphere reflectance, “BT” = brightness temperature, “SR” = surface reflectance, “ST” = land surface temperature, “QA” = quality assessment)|
Table 3. U.S. Landsat Analysis Ready Data (ARD) Package Terms and Definitions
Within each U.S. Landsat ARD Package, a GeoTIFF (.tif) file is included for each band. The terms and definitions for band files are illustrated in Table 4.
Table 4. U.S. Landsat Analysis Ready Data (ARD) Image Product Terms and Definitions
Individual band specifications and other important information about each U.S. Landsat ARD product, along with the QA bit index values, can be found in the U.S. Landsat ARD Data Format Control Book (DFCB).
Search and Download
U.S. Landsat ARD products are available for search and download from EarthExplorer. The U.S. Landsat ARD dataset is the first one listed under the Landsat section on the Data Set tab, as shown in Figure 7 below.
Figure 7. EarthExplorer Data Set tab showing U.S. Landsat ARD
The file sizes of U.S. Landsat ARD products vary greatly, and they have the possibility of being significantly larger than the standard Landsat Level-1 data products. Table 5 lists the estimated average, minimum, and maximum file sizes observed in current U.S. Landsat ARD data products.
Table 5. Estimated Average, Minimum, and Maximum Tile Sizes of U.S. Landsat ARD Products
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 of sample tile h26v08 in Western Pennsylvania indicate this caveat.
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.
U.S. Landsat Analysis Ready Data (ARD) Data Format Control Book (DFCB) .pdf (885 KB)
Contact USGS User Services with any U.S. Landsat ARD-related questions.