# Values IDW interpolation do not decrease

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06-19-2022 11:43 AM
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I use IDW interpolation to see how light intensity is spreading across an area. When I perform IDW the values of the intensity decrease but after a certain distance the values stop to decrease. Then all the values are the same but I would expect them to decrease until the intensity reaches the value of 0. Is IDW incapable of doing this?

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MVP Esteemed Contributor

What is the range of values represented by the points?

According to IDW (Spatial Analyst)—ArcGIS Pro | Documentation, "The output value for a cell using inverse distance weighting (IDW) is limited to the range of the values used to interpolate. Because IDW is a weighted distance average, the average cannot be greater than the highest or less than the lowest input..."

Think Location
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MVP Esteemed Contributor

What is the range of values represented by the points?

According to IDW (Spatial Analyst)—ArcGIS Pro | Documentation, "The output value for a cell using inverse distance weighting (IDW) is limited to the range of the values used to interpolate. Because IDW is a weighted distance average, the average cannot be greater than the highest or less than the lowest input..."

Think Location
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New Contributor

The lowest value is 0.5 so then is makes sense why it will not reach 0. Thanks for your help