I am experimenting with Google Earth Engine and normalized my images using UnitScale as per this post.

When I view the image in the lower pane in Google Earth Engine Code editor and switch the visualization parameters to 100% (from custom: 0-1 - set by the code), I notice that the min and max are nolonger 0-1 but some other range such as 0.03 - 0.56. Sometimes as I pan and zoom, the min and max of 100% changes.

I need to be certain of what is happening here so I can know whether I can trust mathematics on the normalized data. So my question is this:

  1. If your data range already falls between 0-1 (ie min>0 and max<1), does any scaling take place? It is not clear from the documentation for this use-case.
  2. Why do the min and max values change when panning and zooming? I assume this is because the min and max in the pop-up visualization parameters only refere to the portion of the image that is on-screen at a given time - which means that what you see is a 'moveable feast' - zooming out to 100% does not give a range of 0-1 so I assume this is due to resampling at low zoom levels. Are these assumptions correct?
  • I don't see how this is too broad! It is a specific question about a specific usage of a single GEE command. The question can be answered (by somebody who knows) with two words - one for each point. Sep 23, 2019 at 10:12


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