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I am trying to get landsat reflectance values corresponding to field plots spread all over Finland using the Google Earth Engine. As you know, Finland is up North, between latitudes of ~60 and 70 degree N. I am extracting from this landsat collection. Upon examining the extracted values, I noticed that most (99.9%) of the pixels have a 'pixel_qa' value of 322. From my understanding of the bitmask, I gathered that the value of '322' means that the 'cloud confidence' and the 'cirrus confidence' was low. Why is this? Can I still assume that the cloud/noncloud classification is good enough?

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I got a reply from someone at USGS: "You want low confidence in clouds, that means that there is very little chance that there is a cloud there when there shouldn't be. A value of 322 means that the pixels are clear and there are not clouds present."

So, in conclusion, a value of 322 is okay to work with.

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  • Is more than that, you should decode pixel_qa band in the bits you need. Check this question, it could help you gis.stackexchange.com/questions/271322/… – aldo_tapia Jan 27 at 12:23
  • Thanks for that link! Actually, I was confused by what they meant in bits 6-7 and 8-9. For example, a "cloud confidence" value of "none" seems to say that the algorithm has very low confidence on its output (clouds vs no-cloud)! I have given the feedback to the USGS person that they may want to word that better. Something like "probability of cloud contamination in the pixel"... – user7831861 Jan 28 at 16:15
  • As far I know, none is non-determine status. Check this page: usgs.gov/core-science-systems/nli/landsat/… – aldo_tapia Jan 28 at 19:38

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