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A friend and I are working with remotely sensed imagery and need to extract surface reflectance values for a specific set of points. I did so using QGIS and he did using Google Earth Engine, but our values are much different (the values extracted from Earth Engine were much higher than the values extracted from QGIS). We used the same images, set of points, and surface reflectance bands. In QGIS, I used the point sampling tool, and in Earth Engine, my friend used the function sampleRegions. Does anyone know why this might be happening?

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Probably there might be some difference in the scaling of values of surface reflectance between GEE and QGIS. Please also make sure they have the same coordinate reference system.

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  • brentiemapper is right that it's probably just scaling values. Check the Bands section of the dataset description to see what the scaling factor are for the dataset you're using. But, you can't reproject an ImageCollection like that, and you shouldn't be using reproject at all. The sampleRegion function takes a crs and scale; just make sure that they're the same as whatever you're using in QGIS. Jul 6, 2021 at 14:29
  • Thanks @NoelGorelick, I think this the reproject is just applicable for a single image? I'll edit my response. Jul 8, 2021 at 9:39
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USGS surface reflectance (SR) products are stored in unsigned 16-bit integer format to reduce data size. Read more here.

By default the SR products in Google Earth (GE) are scaled the same way. Read more here.

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