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According to ESRI's help files, NN interpolation calculates a value for a "query point", yet the output is ofcourse a raster.

I understand how the value of this query point is calculated based on the Voronoi diagram, but how is the eventual raster generated?

Regarding IDW, ESRI's help does mention that "The specified fixed search radius will be used for each interpolated cell (cell center) in the study area".

Should i assume that the weights, and not only the search radius itself, are calculated from the cell center?

Should i then assume that NN also refers to the centers of cells?

I have run my own experiments and my conclusion is that yes, the weights for IDW are calculated from the center of each cell, and for NN the "query point" is stationed in the center of the raster cell. Perhaps later i will add my calculations.

  • As per the Tour there should be only one question asked per question. – PolyGeo Sep 19 '16 at 2:28
  • @polygeo for me the question is "do spatial interpolation tools from ArcGIS use the center of the pixels ? and the answer is yes, but I agree that it would be easier to split NN and IDW in two questions – radouxju Sep 19 '16 at 5:45
  • @radouxju I'll re-open the question so that you can put that in a few sentences that expand just a little on a simple yes. – PolyGeo Sep 19 '16 at 5:47
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The value of the cell in ArcGIS is located in its center. As far as I know, all raster analysis tools (distance tools, interpolation tool) are logically also using the center of the cell. However, one should be careful about the source of the raster cells: when a vector feature is used as input, they are internally fitted to the center of the cell and might therefore "move" before the computation.

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