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For computing the NDVI I want to use USGS Landsat 8 Collection 2 Tier 1 TOA Reflectance LANDSAT/LC08/C02/T1_TOA does it need cloud masking or any other form of ''cleaning'' before I can use it?

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The Landsat 8 Collection 2 encompasses Level-1 (top of atmosphere reflectance) and Level-2 (atmospherically corrected surface reflectance) products. Since Landsat 8 Collection 2 level-2 correspond to surface reflectance and;

corrected for the temporally, spatially and spectrally varying scattering and absorbing effects of atmospheric gases, aerosols, and water vapor

it should be used to generate NDVI.

However, you need to apply scaling factor i.e., 0.0000275 + -0.2 for Level-2 before calculating NDVI. You should mask pixels which are contaminated by clouds and shadows as well.

Here, I would recommend a worth reading article "A survival guide to Landsat preprocessing" for further enlightenment.

More information about Landsat Collection 2 Level-2 Science Products can be accessed from here.

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  • Are you sure about the scaling factor for LANDSAT/LC08/C02/T1_TOA on GEE? I am new to all of this but here are two observations: 1) the GEE guide here shows how to calculate NDVI and does not use any scaling. Just image.normalizedDifference(['B5', 'B4']).rename('NDVI') where image is from the LANDSAT/LC08/C02/T1_TOA collection. 2) Before scaling, values should be between 1-65455 but I see values such as 0.2 for B5 in my quick check. Commented Mar 16, 2023 at 2:10
  • Please see the link added in answer for more information
    – Dave
    Commented Mar 17, 2023 at 10:14
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Yes. There are examples in the code editor for doing cloud and shadow masking.

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