Web-enabled Landsat data (WELD) Project

The WELD products are stored in Hierarchical Data Format (HDF). In this version, each WELD pixel has 18 bands (termed HDF science data sets) storing the information described in the Table below. 

WELD Product Spatial Format

The WELD products are stored in separate files, each file is a tile of 5000 x 5000 30 m pixels defined in the Albers Equal Area projection. 

There are a total of 501 CONUS and 162 Alaskan land tiles referenced using a two digit horizontal and vertical tile coordinate system that is reflected in the product filename.  The images below illustrate the tile coordinate systems, please click on them to see higher resolution versions.

The WELD data products are available from this EROS web site by clicking HERE.  

For each WELD tile there is a corresponding static Alaska.latlon.h<xx>v<yy>.hdf or CONUS.latlon.h<xx>v<yy>.hdf  file that contains the geographic latitude and longitude for the center of each 30m pixel (decimal degrees, scale factor 1, data type double, datum WGS84).   A WELD tile location tool is also provided to locate pixels and tiles for given longitude and latitude coordinates.  The tool is available for computers running Unix/Linux operating systems, the C source code and installation instructions can be downloaded HERE. 

Each WELD product tile is typically 300MB, the file size varies as the data are stored in Hierarchical Data Format with internal compression activated.  Each static geographic latitude and longitude file is 314 MB.  

WELD Product Data Citation

Roy, D.P., Ju, J., Kline, K., Scaramuzza, P.L., Kovalskyy, V., Hansen, M.C., Loveland, T.R., Vermote, E.F., Zhang, C., 2010, Web-enabled Landsat Data (WELD): Landsat ETM+ Composited Mosaics of the Conterminous United States, Remote Sensing of Environment, 114: 35-49.

Funding

The WELD project is funded by NASA’s Making Earth System Data Records for Use in Research Environments (MEaSUREs) program with significant USGS cost sharing.  The aim of the MEaSUREs program is to support projects providing services and consistent long term Earth science data products driven by NASA’s Earth science goals and contributing to advancing NASA’s “missions to measurements” concept.  The WELD project contributes to the Land measurement theme.

The WELD project is a collaboration between the United States Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) and its academic partner, the South Dakota State University Geographic Information Science Center of Excellence (GIScCE). 

Future Improvements

The WELD processing is being prototyped at the GIScCE with planned systematic processing to be undertaken at EROS. The WELD processing is being developed to improve the consistency and quality of Landsat ETM+ data through a fusion with contemporaneous MODIS land products. The WELD data products will be updated in near real time and made available to the user community through a dedicated internet distribution interface.  More years of composited mosaic products and future versions with refined processing and content will be provided, most notably atmospheric correction, radiometric/BRDF normalization, cloud and ETM+ SLC-off gap filling, and land cover characterization.  For more information on the WELD project and products please contact David Roy.