The Landsat Collection 1 Level-1 Quality Assessment (QA) 16-bit band contains unsigned integers that represent bit-packed combinations of surface, atmospheric, and sensor conditions that can affect the overall usefulness of a given pixel.
The following conditions are available:
Each of these values can be obtained using our utility function named decodeLs8Qa. The function returns a dictionary of all conditions, where each condition contains an extracted value. Here is a working example script for extracting cloud values of the BQA band, with the other options commented below:
return [decodeLs8Qa(BQA).cloud]
//return [decodeLs8Qa(BQA).designatedFill]
//return [decodeLs8Qa(BQA).occlusion]
//return [decodeLs8Qa(BQA).radiometricSaturation * 0.33]
//return [decodeLs8Qa(BQA).cloudConfidence * 0.33]
//return [decodeLs8Qa(BQA).cloudShadowConfidence * 0.33]
//return [decodeLs8Qa(BQA).snowIceConfidence * 0.33]
//return [decodeLs8Qa(BQA).cirrusConfidence * 0.33]
Visit EO Browser to see the script for:
Example interpretation: when using evalscript for Cloud, value 0 means clouds are not present, and value 1 means clouds are present. In EO Browser, we can observe clouds in white, and all other pixels in black. Below are value interpretations for each of the available conditions.
Note: in the following tables, the color column represents a color legend for the EO Browser visualization, using the scripts listed above. The values could be visualized with different colors, if a different visualization was used.
Value | Description | Color |
---|---|---|
0 | This condition does not exist | |
1 | This condition exists |
Value | Description | Color |
---|---|---|
0 | No bands contain saturation | |
1 | 1-2 bands contain saturation | |
2 | 3-4 bands contain saturation | |
3 | 5 or more bands contain saturation |
Value | Description | Color |
---|---|---|
0 | Not Determined (algorithm did not determine the status of this condition) / No (this condition does not exist) | |
1 | Low - algorithm has low to no confidence that this condition exists (0-33 percent confidence) | |
2 | Medium - algorithm has medium confidence that this condition exists (34-66 percent confidence) | |
3 | High - algorithm has high confidence that this condition exists (67-100 percent confidence) |