WELDAKWK v015

NASA Web-Enabled Landsat Data Alaska Weekly


PI: David Roy

Description

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).

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Characteristics

Improvements/Changes from Previous Versions

Version 1.5 is the original version.

Collection and Granule

Collection

Characteristic Description
CollectionMEaSUREs WELD and GWELD
DOI10.5067/MEaSUREs/WELD/WELDAKWK.001
File Size~101 MB
Temporal ResolutionMulti-Day
Temporal Extent2003-01-22 to 2012-12-29
Spatial ExtentAlaska (United States)
Coordinate SystemAlbers Equal Area
DatumWorld Geodetic System (WGS84)
File FormatHDF4
Geographic Dimensions150 km x 150 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers14
Columns/Rows5000 x 5000
Pixel Size30 m

Layers

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.

Decision Tree Cloud Classification

Class Description
0 Not cloudy
1 Cloudy
2 Not cloudy but adjacent to a cloudy pixel
200 Could not be classified reliably

ACCA Cloud Classification

Class Description
0 Not cloudy
1 Cloudy

Product Quality

WELD Version 1.5 product quality information can be found on the WELD Project website.

Known Issues

WELD Version 1.5 known issues can be found on the WELD Project website.

Documentation

Using the Data

Tools

Citation

DOI: 10.5067/MEaSUREs/WELD/WELDAKWK.001

About the Image

NASA Web-Enabled Landsat Alaska weekly reflectance data from the WELDAKWK product over Alaska, United States, week of June 3, 2012.

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