Quality Assessment (QA) bands help to evaluate the overall usefulness of a Landsat pixel. Each pixel in the QA band contains an integer value that represents bit-packed combinations of surface, atmospheric, and sensor conditions that can affect the individual pixel quality.
QA bands are provided with Landsat Collection 1 and Collection 2 Level-1 data and Level-2 science products.
Return to Landsat Quality Assessment Tools Overview
This ArcGIS-based toolbox provides functionality to classify and/or extract bit packed values for the QA bands provided with the Landsat Collection 1 (C1) and Collection 2 (C2) Level-1 and Level-2 science products. The Landsat Quality Assessment (QA) Tools provide the functionality of extracting bit packed values to individual bands for the Landsat Level-1 BQA band only.
Compatible Products
The Landsat QA ArcGIS Toolbox is compatible with all Landsat Collection 1 and Collection 2 Level-1 and Landsat Level-2 Science Data QA bands. The table below describes each band’s properties.
| Band | Source |
|---|---|
| BQA Product: Level-1 Provides information about the quality of surface, atmospheric, and sensor conditions that can affect the overall usefulness of a given pixel |
C1/C2 Level-1 |
| pixel_qa Product: TOA, SR, SI Populated from C1/C2 Level-1 BQA. Provides information about cloud confidence, cloud shadow, and snow/ice. |
C1/C2 Level-2 Surface Reflectance |
| radsat_qa This band is a bit-packed representation of which sensor bands were saturated during data capture, yielding unusable data |
C1/C2 TOA, SR, SI |
| sr_cloud_qa Provides per-pixel information about dense dark vegetation, cloud, cloud shadow, adjacency to cloud, snow, and water |
C1/C2Landsat 4-7 SR (LEDAPS) |
|
sr_aerosol |
C1/C2 Landsat 8 SR (LaSRC) |
| L2_flags Product: Landsat 8 Aquatic Reflectance Provides per-pixel information about success or failure of processing and validity of sun glint, view angle, solar angle, polarization, chlorophyll-a, etc. |
C1 Level-2 Provisional Aquatic Reflectance |
BQA Level-1 Quality Assessment Band File, LaSRC Land Surface Reflectance Code, LEDAPS Landsat Ecosystem Disturbance Adaptive Processing System, SI Spectral Indices, SR Surface Reflectance, TOA Top of Atmosphere Reflectance
Download Landsat QA ArcGIS Toolbox
The Landsat QA ArcGIS Toolbox provides functionality to classify and/or extract bit packed values for all Collection 1 and Collection 2 Level-1 and Level-2 science product QA bands. The use of this tool enhances the applications of interpretation, mapping and applying QA values to all Landsat data products.
The Landsat QA ArcGIS Toolbox includes the following tools:
Decode QA – decodes bit-packed quality information from Landsat Collection 1 and Collection 2 Level-1 and Level-2 QA bands. Unlike bit-unpacking tools, Decode does not generate new bands, but instead builds an attribute table from the input and populates each unique value with its respective classification.
Extract QA Bands – finds all unique values in the QA band, and extracts classes individually, as defined by user input. The tool then writes each class to a new image file, and provides the option to combine all selected classes into a single file.
The Landsat QA ArcGIS Toolbox README file contains installation instructions and all pertinent details for each tool.
Toolbox Caveats
The toolbox was designed using ArcGIS version 10.4.1 and Python version 2.7.10. The functionality of the toolbox cannot be guaranteed for previous software versions, and cross-compatibility of newer and future ArcGIS and Python releases are subject to vendor discretion. Other caveats include:
- Input data must be in GeoTIFF (.tif), binary (.img), or other single-band raster format supported by ArcGIS.
- Input data must be stored in integer format; any float, double, or complex data types are not supported.
- Any band with values outside of the supported range will not process.
- If using non-standard (i.e., user modified) file naming conventions, the tool may not correctly identify the band type, which may result in incorrect output products. Ensure the “sensor” and “band” categories are set accordingly.
- Due to an issue with the Clear bit in Landsat 4-7 Collection 2 data, users should cease reliance on the QA Clear bit (bit 6) alone and engage the QA “Dilated Cloud” (bit 1) AND “Cloud” (bit 3) OFF condition to correctly identify clear pixels over water. Please visit the Landsat Collection 2 Known Issues page for more details about this issue.
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