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WELDAKMO V015

10.5067/MEaSUREs/WELD/WELDAKMO.001
NASA Web-Enabled Landsat Data Alaska Monthly
WELDAKMO

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 2002 to 2012. These mosaics provide consistent data for deriving land cover, and geophysical, biophysical products for regional assessments of surface dynamics for effective study of Earth system function. The Alaska Monthly products are defined with respect to each calendar year by the days in each month. 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. These products are distributed in Hierarchical Data Format 4 (HDF4).

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).

Improvements/Changes from Previous Versions

Version 1.5 is the original version.

Collection

Characteristic Description
Temporal Granularity Static
Temporal Extent January 1, 2003 - November 30, 2012
Spatial Extent Alaska (United States)
File Size ~148 MB
Coordinate System Albers Equal Area
Datum World Geodetic System (WGS84)
File Format HDF
Geographic Dimensions ~150 km x 150 km
Total Number of Tiles 13472
Total Size ~1953 GB

 

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers 14
Columns/Rows 5000 x 5000
Pixel Size 30 m

 

Data Layer Characteristics

SDS Name Description Units Data Type Fill Value Valid Range Scale Factor
Band1_TOA_REF

Band 1 Top of Atmosphere reflectance

N/A 16-bit signed integer

-32768

-32767 to 32767

0.0001
Band2_TOA_REF

Band 2 Top of Atmosphere reflectance

N/A 16-bit signed integer

-32768

-32767 to 32767

0.0001
Band3_TOA_REF

Band 3 Top of Atmosphere reflectance

N/A 16-bit signed integer

-32768

-32767 to 32767

0.0001
Band4_TOA_REF

Band 4 Top of Atmosphere reflectance

N/A 16-bit signed integer

-32768

-32767 to 32767

0.0001
Band5_TOA_REF

Band 5 Top of Atmosphere reflectance

N/A 16-bit signed integer

-32768

-32767 to 32767

0.0001
Band61_TOA_BT

Band 6 Top of Atmosphere and Brightness Temperature resampled to 30 m

Degrees Celsius 16-bit signed integer

-32768

-32767 to 32767

0.01
Band62_TOA_BT

Band 6 Top of Atmosphere and Brightness Temperature resampled to 30 m

Degrees Celsius 16-bit signed integer

-32768

-32767 to 32767

0.01
Band7_TOA_REF

Band 7 Top of Atmosphere and Brightness Temperature

N/A 16-bit signed integer

-32768

-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

-10000 to 10000

0.0001
Day_Of_Year

Day of year the selected ETM+ pixel was sensed on¹

Day 16-bit signed integer

0

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.

N/A 8-bit unsigned integer

N/A

0 to 255

N/A
DT_Cloud_State

Decision Tree Cloud Classification

N/A 8-bit unsigned integer

255

0, 1, 2, 200

N/A
ACCA_State

Automatic Cloud Cover Assessment Algorithm (ACCA) State

N/A 8-bit unsigned integer

255

0, 1

N/A
Num_Of_Obs

Number of ETM+ observations considered over the compositing period

N/A 8-bit unsigned integer

N/A

0 to 255

N/A

 

¹ Note (a) days 1-334 (or 1-335) were sensed in January-November of the non-leap (or leap) current year; (b) days 335-365 (or 336-366) were sensed 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.

Pixel Values

Pixel Value DT Cloud State (Decision Tree) ACCA_State (ACCA Cloud Classification)
0 Not cloudy Not cloudy
1 Cloudy Cloudy
2 Not cloudy but adjacent to a cloudy pixel N/A
200 Could not be classified reliably N/A

 

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.

WELDAKMO
PI Name: 
David Roy
Decommissioned: 
False