I have three points (boreholes) on the map. I created them using shape file layer. Each borehole shape file layer shows the strati-graphic section of the ground. (i.e. between 0-50 m = Gravel , 50-60 m = Sand , 60-80 m = Clay.) Rocks are located in different depths for different boreholes. So I need to interpolate these three points to create continuous surface with 3 boreholes.

I'm pretty new to QGIS, so it's better if someone could give me the instructions in detail since I tried to find what I look for from the questions that were asked before, but couldn't.

I want to create a continuous surface from 3 points of different borehole data to find the intermediate. I want to assume that the geological structure under the ground is same everywhere. I need to interpolate these three data sets to find an average subsurface model.

These are the boreholes: 3 points (boreholes)

The thing that I do was to click interpolation under "raster", and then I chose one of the boreholes & added it. For cellsize X and Y I put 300, after I entered an output file name, I clicked OK but nothing comes to the layers panel. I tried the same thing for both TIN and IDW, but it didn't work.

If I add another thing (For example Heidelberg contour) instead of adding borehole that I created, then it works, at least something comes to the layers panel after I click OK. From the image you see below, nothing comes to the layers panel when I click OK. Interpolation

And this is the attribute table for Borehole_A : Attribute table

  • 2
    Welcome to GIS.SE. Scientifically three points are awfully few points to interpolate from. Also, what exactly do you want to obtain from the interpolation? An image or an example of your data would be rather helpful, too. Also it'd be better if you pointed out what you tried already and where you are stuck.
    – Erik
    Apr 3, 2019 at 15:06
  • Thank you for your answer! I edited my question and added some images. If you could look at it again and help me I'd appreciate it :) Apr 4, 2019 at 8:28
  • maybe this tutorial will give you a start: qgistutorials.com/en/docs/interpolating_point_data.html
    – PieterB
    Apr 4, 2019 at 9:28
  • I assume "3 points" means "3 locations", and each location has different types of (ground) layer as a point feature in own layer (in GIS terminology). It's not clear in your question. And what do you mean by intermediate? At least I couldn't understand that. Apr 4, 2019 at 10:39
  • Yes, "3 points" means "3 locations". I am so sorry, I've just started using QGIS, so I don't have the terminology. Each location has the same rock types (Gravel, Sand, Sand&Clay&Marl , Sand&Clay) but the thicknesses of the rocks are changing at each location. For example for the location number 1, thickness of gravel is 60 m, for the location number 2, thickness of gravel is 30 m etc... Apr 4, 2019 at 14:48

1 Answer 1


I figured it out. You can see the attribute table below.

Attribute table

Before, I was adding 3 different shape files to add 3 locations. After I did the same thing with only one shape file (and three different locations [points]) it worked. I also had to remove the Type (text) column, otherwise it didn't work again.

  • 1
    Mark your answer as the correct one, so other users know that this is the solution. Apr 4, 2019 at 18:19

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