Quality Assessment (QA) bands are a helpful resource for evaluating 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 currently provided with Collection 1 based products, including Landsat Level-1 Standard Data Products and Higher Level Science Data Products. The already-established Landsat Quality Assessment (QA) Tools provide the functionality of extracting bit packed values to individual bands for only the Landsat Level-1 BQA band; this ArcGIS-based toolbox provides functionality to classify and/or extract bit packed values for all Level-1 and Higher-Level QA bands.
The Landsat QA ArcGIS Toolbox is compatible with all Landsat Collection 1 Level-1 and Higher-Level QA bands. The table below describes each band’s properties.
|Level-1||Standard Level-1 Product||Landsat Collection 1 Level-1 Quality Assessment Band|
|Higher-Level||TOA, SI, SR||Landsat Surface Reflectance Quality Assessment|
|TOA, SI, SR|
|Landsat 4-7 SR (LEDAPS)|
|Landsat 8 SR (LaSRC)|
BQA Level-1 Quality Assurance Band File, LaSRC Landsat Surface Reflectance Code, LEDAPS Landsat Ecosystem Disturbance Adaptive Processing System, SI Spectral Indices, SR Surface Reflectance, TOA Top of Atmosphere Reflectance
The Landsat QA ArcGIS Toolbox provides functionality to classify and/or extract bit packed values for all Level-1 and Higher-Level QA bands, which are listed in the table below. 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 Level-1 and Higher-Level 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.
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:
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