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I am using image and collection reducers to extract mean values of several assets (for example, prism precipitation and pml2 ET) from within USGS watershed boundaries which I load in as geometries. I am generally extracting data at 1000m scale.

I am having no problem with this workflow, however I am wondering what GEE does to determine which pixels qualify as within the geometry? (Is it based on the centroid or edge or another calculation?)

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  • Weighted reducers (e.g. ee.Reducer.mean()): pixels are included if at least (approximately) 0.5% of the pixel is in the region and the image's mask is non-zero; their weight is the minimum of the image's mask and the (approximate) fraction of the pixel covered by the region.

Quoted straight from following GEE tutorial: https://developers.google.com/earth-engine/guides/reducers_reduce_region

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  • Thank you so much, @korndog! Don't know how I missed that! I don't have enough reputation to officially upvote you on GIS stack overflow, but I will return and complete that task when I do. Thanks again!
    – Elmstead
    Jan 28, 2021 at 14:32

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