NASA Web-Enabled Landsat Alaska annual reflectance data from the WELDAKYR product over Alaska, United States, 2011.
View full-size imageNASA’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 products 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. WELDAKYR is distributed in Hierarchical Data Format 4 (HDF4).
The annual products include the preceding year’s December through the current year’s November.
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.
| Characteristic | Description |
|---|---|
| Collection | MEaSUREs WELD and GWELD |
| DOI | 10.5067/MEaSUREs/WELD/WELDAKYR.001 |
| File Size | ~181 MB |
| Temporal Resolution | Yearly |
| Temporal Extent | 2002-12-01 to 2012-11-30 |
| Spatial Extent | Alaska (United States) |
| Coordinate System | Albers Equal Area |
| Datum | World Geodetic System (WGS84) |
| File Format | HDF4 |
| Geographic Dimensions | 150 km x 150 km |
| Characteristic | Description |
|---|---|
| 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.
| Class | Description |
|---|---|
| 0 | Not cloudy |
| 1 | Cloudy |
| 2 | Not cloudy but adjacent to a cloudy pixel |
| 200 | Could not be classified reliably |
| Class | Description |
|---|---|
| 0 | Not cloudy |
| 1 | Cloudy |
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.