NASA Web-Enabled Landsat Alaska weekly reflectance data from the WELDAKWK product over Alaska, United States, week of June 3, 2012.View full-size image
NASA’s Web-Enabled Landsat Data (WELD) are generated from composited 30 meter (m) Landsat Enhanced Thematic Mapper Plus (ETM+) mosaics of the United States and Alaska from 2003 to 2012. These mosaics provide consistent data to derive land cover, geophysical, and biophysical products for regional assessments of surface dynamics for effective study of Earth system function. This product includes Top of Atmosphere (TOA) Reflectance and Brightness Temperature, along with the Normalized Difference Vegetation Index (NDVI) generated from Band 3 and Band 4 TOA Reflectance. WELDAKWK is distributed in Hierarchical Data Format 4 (HDF4).
The WELD weekly products are defined with respect to each calendar year and as consecutive 7 day products with the following examples defined for the weeks: Week01: January 1 to January 7 Week02: January 8 to January 14 Week52: December 24 to December 30 (non-leap years) Week52: December 23 to December 29 (leap years) Week53: December 31 (non-leap years) Week53: December 30 to December 31 (leap years)
The WELD project is funded by the National Aeronautics and Space Administration (NASA) and is a collaboration between the United States Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center and the South Dakota State University (SDSU) Geospatial Sciences Center of Excellence (GSCE).
Version 1.5 is the original version.
|Collection||MEaSUREs WELD and GWELD|
|File Size||~101 MB|
|Temporal Extent||2003-01-22 to 2012-12-29|
|Spatial Extent||Alaska (United States)|
|Coordinate System||Albers Equal Area|
|Datum||World Geodetic System (WGS84)|
|Geographic Dimensions||150 km x 150 km|
|Number of Science Dataset (SDS) Layers||14|
|Columns/Rows||5000 x 5000|
|Pixel Size||30 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|Band1_TOA_REF||Band 1 Top of Atmosphere reflectance||N/A||16-bit signed integer||-32768||N/A||-32767 to 32767||0.0001|
|Band2_TOA_REF||Band 2 Top of Atmosphere reflectance||N/A||16-bit signed integer||-32768||N/A||-32767 to 32767||0.0001|
|Band3_TOA_REF||Band 3 Top of Atmosphere reflectance||N/A||16-bit signed integer||-32768||N/A||-32767 to 32767||0.0001|
|Band4_TOA_REF||Band 4 Top of Atmosphere reflectance||N/A||16-bit signed integer||-32768||N/A||-32767 to 32767||0.0001|
|Band5_TOA_REF||Band 5 Top of Atmosphere reflectance||N/A||16-bit signed integer||-32768||N/A||-32767 to 32767||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_TOA_REF||Band 7 Top of Atmosphere and Brightness Temperature||N/A||16-bit signed integer||-32768||N/A||-32767 to 32767||0.0001|
|NDVI_TOA||Normalized Difference Vegetation Index (NDVI) value generated from Band3_TOA_REF and Band4_TOA_REF||N/A||16-bit signed integer||-32768||N/A||-10000 to 10000||0.0001|
|Day_Of_Year¹||Day of year the selected ETM+ 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) State||Class||8-bit unsigned integer||255||N/A||0, 1||N/A|
|Num_Of_Obs||Number of ETM+ observations considered over the compositing period||Number||8-bit unsigned integer||N/A||N/A||0 to 255||N/A|
¹Note (a) days 1-334 (or 1-335) were acquired in January-November of the non-leap (or leap) current year; (b) days 335-365 (or 336-366) were acquired in December of the non-leap (or leap) previous year; (c) in the annual composite of a leap year, day 335 always means November 30.
|2||Not cloudy but adjacent to a cloudy pixel|
|200||Could not be classified reliably|
WELD Version 1.5 product quality information can be found in section 6 of the WELD ATBD.
WELD Version 1.5 known issues can be found on the page 21 of the WELD Version 1.5 User Guide.