Two Web-enabled Landsat Data (WELD) projects have produced large area 30-meter composited mosaics from Landsat terrain corrected (Level-1T) data. Both projects are funded by NASA's Making Earth System Data Records for Use in Research Environments program with significant USGS cost sharing.
The WELD data products are processed so users do not need to apply the equations, spectral calibration coefficients, and solar information, needed to convert Landsat digital numbers to reflectance and brightness temperature. They are defined in the same coordinate system and align precisely, making them simple to use for multi-temporal applications. The products provide consistent data that can be used to derive higher-level land cover as well as geo-physical and biophysical products for assessment of surface dynamics and to study Earth system functioning. WELD data products are available to download for all users at no charge.
Figure 1. Annual composites of conterminous United States (CONUS).
Available Data Products
Monthly and annual 30-meter global composites generated from contemporaneous Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 5 Thematic Mapper (TM) data for all non-Antarctic land surfaces are available for 3-year epochs. Products are available in Geographic Tagged Image File Format (GeoTIFF) through an interactive Web interface, or as Hierarchical Data Format (HDF) tiles from a direct download site.
The Global WELD Available Data Products page provides information about the Global WELD products, known issues, and future plans.
CONUS and Alaska WELD
Weekly, monthly, seasonal and annual 30-meter continental U.S. (CONUS) and Alaska composites generated from Landsat 7 ETM+ data are available for 10 years (2003-2012). Products are available in Geographic Tagged Image File Format (GeoTIFF) through an interactive Web interface, or as Hierarchical Data Format (HDF) tiles from a direct download site.
The CONUS and Alaska WELD Available Data Products page provides information about the CONUS and Alaska WELD products, known issues, and future plans.
WELD products do not include metadata files, other than basic specifications written into headers or tags. Quality information can be requested with an order, however, such as pixel source parameters, saturation flags, and cloud states.
The Metadata page includes a section “Version 1.5 Product Documentation” that contains product content, format, and projection information.
As a static collection, WELD products are not actively checked for quality characteristics that might otherwise affect the integrity of data values.
The Quality page for Global WELD includes a section on “Version 2.2 Product Quality” with useful information about known issues, product improvements, accuracy, consistency, and future plans.
The Quality page for CONUS and Alaska WELD includes a section on “Version 1.5 Product Quality” with useful information about known issues, product improvements, accuracy, consistency, and future plans.
WELD products are available for download from the following pages.