This question is an exact duplicate of:

I am new to ArcGIS.

I have a data set with air pollution concentrations for 20 locations in the Netherlands. I would like to interpolate this data with IDW, so that I can estimate the approximate concentration for every address in the Netherlands.

I used the IDW geoprocessing tool in ArcGIS Pro. My problem is, that the estimation only is made for between the data points, which leaves the parts at the borders of the country without estimation (see image). IDW interpolation, borders not included

What I would like is to expand the size of the interpolation that all of the Netherlands is captured in the estimation.

I symbolized the Netherlands in this way:


I tried to define the extent of the interpolation in the IDW geoprocessing tool with the shape of the country that I acquired with the method in the link (under Environments, I set Extent to: Same as layer 'The Netherlands'). But then the interpolation is spread out way too far, like 10x the surface of the Netherlands.

Does this mean I should select the country in a different way to make it work?

marked as duplicate by KHibma, whyzar, Andre Silva, Fezter Oct 30 '18 at 23:05

This question was marked as an exact duplicate of an existing question.


Go to Analysis tab, Geoprocessing ribbon and click in Enviroments. In Processing Extent select the shapefile as Extent and in Raster Analysis select the same Netherlands shapefile as Mask.

enter image description here

By the way, this is not "expand IDW borders". What you want to do is an extrapolation.

  • The first part of your answer is a good explanation of geoprocessing environments, but it doesn't answer the question. Your second point is relevant. – KHibma Oct 30 '18 at 12:40
  • Thanks for your answer. It turns out I had to save the shape of the Netherlands as feature class and use this to set the extent. Before I used my dataset to define the extent, which didn't help of course. And yes, extrapolation... – Qeshet Oct 31 '18 at 15:31
  • I tried interpolation with the Geostatistical Wizard just now, and I have exactly the same problem as before. I have set processing extent in Environments right, but that doesn't help. I have two separate files now. One shapefile with the data points and one feature class file with the border of the Netherlands. Do I have to combine the two in some way? Thanks! – Qeshet Nov 1 '18 at 9:25
  • Border shapefile has .prj file? Are both shapefiles in the same coordinate system? – aldo_tapia Nov 1 '18 at 11:07
  • I feel very confused right now, so I made a new question: gis.stackexchange.com/questions/301984/… Too much of a beginner in ArcGIS I am afraid. :O – Qeshet Nov 9 '18 at 8:55

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