The NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Global Web-Enabled Landsat Data Annual (GWELDYR) Version 3.1 data product provides Landsat data at 30 meter (m) resolution for terrestrial non-Antarctica locations over annual reporting periods. GWELD data products are generated from all available Landsat 4 and 5 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data in the U.S. Geological Survey (USGS) Landsat archive. The GWELD suite of products provide consistent data to derive land cover as well as geophysical and biophysical information for regional assessment of land surface dynamics.
The GWELD products include Nadir Bidirectional Reflectance Distribution Function (BRDF)-Adjusted Reflectance (NBAR) for the reflective wavelength bands and to top of atmosphere (TOA) brightness temperature for the thermal bands. The products are defined in the Sinusoidal coordinate system to promote continuity of NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) land tile grid.
Provided in the GWELDYR product are layers for surface reflectance bands 1 through 5 and 7, TOA brightness temperature for thermal bands, Normalized Difference Vegetation Index (NDVI), day of year, ancillary angle, and data quality information. A low-resolution red, green, blue (RGB) browse image of bands 5, 4, 3 is also available for each granule.
Version 3.1 products use Landsat Collection 1 products as input and have improved per-pixel cloud mask, new quality data, improved calibration information, and improved product metadata that enable view and solar geometry calculations.
|Collection||MEaSUREs WELD and GWELD|
|File Size||~370 MB|
|Temporal Extent||1989-01-01 to 2001-12-31|
|Spatial Extent||Global (Non-Antarctic)|
|Datum||World Geodetic System (WGS84)|
|Geographic Dimensions||150 km x 150 km|
|Number of Science Dataset (SDS) Layers||24|
|Columns/Rows||5295 x 5295|
|Pixel Size||30 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|Band1_SRF_REF||Band 1 Surface Reflectance||N/A||16-bit signed integer||-32768||N/A||-2000 to 16000||0.0001|
|Band2_SRF_REF||Band 2 Surface Reflectance||N/A||16-bit signed integer||-32768||N/A||-2000 to 16000||0.0001|
|Band3_SRF_REF||Band 3 Surface Reflectance||N/A||16-bit signed integer||-32768||N/A||-2000 to 16000||0.0001|
|Band4_SRF_REF||Band 4 Surface Reflectance||N/A||16-bit signed integer||-32768||N/A||-2000 to 16000||0.0001|
|Band5_SRF_REF||Band 5 Surface Reflectance||N/A||16-bit signed integer||-32768||N/A||-2000 to 16000||0.0001|
|Band61_TOA_BT||Band 6 Top of Atmosphere and Brightness Temperature resampled to 30 m; low gain||°C||16-bit signed integer||-32768||N/A||-32767 to 32767||0.01|
|Band62_TOA_BT||Band 6 Top of Atmosphere and Brightness Temperature resampled to 30 m; high gain||°C||16-bit signed integer||-32768||N/A||-32767 to 32767||0.01|
|Band7_SRF_REF||Band 7 Surface Reflectance||N/A||16-bit signed integer||-32768||N/A||-2000 to 16000||0.0001|
|NDVI_SRF||Normalized Difference Vegetation Index (NDVI) value||N/A||16-bit signed integer||-32768||N/A||-10000 to 10000||0.0001|
|Day_Of_Year||Day of year the selected Landsat pixel was acquired||Day||16-bit signed integer||0||N/A||1 to 366||N/A|
|Saturation_Flag||The least significant bit to the most significant bit corresponds to bands 1, 2, 3, 4, 5, 61, 62, 7; with a bit set to 1 signifying saturation in that band and 0 not saturated||Bit Field||8-bit unsigned integer||N/A||N/A||0 to 255||N/A|
|DT_Cloud_State||Decision Tree Cloud Classification||Class||8-bit unsigned integer||255||N/A||0 to 2, 200||N/A|
|ACCA_State||Automatic Cloud Cover Assessment Algorithm (ACCA) Classification||Class||8-bit unsigned integer||255||N/A||0, 1||N/A|
|Num_Of_Obs||Number of observations considered over the composition period||Number||16-bit unsigned integer||N/A||N/A||0 to 65534||N/A|
|Composite_Path||Internal compositing algorithm pathway code||N/A||8-bit unsigned integer||N/A||N/A||0 to 15||N/A|
|Sensor||Landsat satellite that the pixel was selected from (4=Landsat 4 TM, 5=Landsat 5 TM, 7 = Landsat 7 ETM+)||N/A||8-bit unsigned integer||255||N/A||0 to 254||N/A|
|Sensor_Zenith||Sensor zenith (nadir = 0 degrees)||Degree||16-bit signed integer||-32768||N/A||0 to 9000||0.01|
|Sensor_Azimuth||Sensor azimuth||Degree||16-bit signed integer||-32768||N/A||-18000 to 18000||0.01|
|Solar_Zenith||Solar zenith of pixel observation (directly overhead = 0 degrees)||Degree||16-bit signed integer||-32768||N/A||0 to 9000||0.01|
|Solar_Azimuth||Sensor azimuth||Degree||16-bit signed integer||-32768||N/A||-18000 to 18000||0.01|
|NBAR_Solar_Zenith||Solar zenith used for NBAR generation of pixel surface reflectance value||Degree||16-bit signed integer||-32768||N/A||0 to 9000||0.01|
|L1T_Index||Index to the L1T image that the pixel was selected from||N/A||16-bit unsigned integer||65535||N/A||0 to 65534||N/A|
|L1T_Column||Pixel column number in the input Level 1T image||N/A||16-bit unsigned integer||65535||N/A||0 to 10000||N/A|
|L1T_Row||Pixel row number in the input Level 1T image||N/A||16-bit unsigned integer||65535||N/A||0 to 10000||N/A|
|2||Not cloudy but adjacent to a cloudy pixel|
|200||Could not be classified reliably|
GWELD Version 3.1 product quality information can be found on the GWELD Project website.
GWELDYR known issues can be found in Section 4 of the Algorithm Theoretical Basis Document (ATBD).