When using the interpolation plugin over the OS terrain data for national grid square NU, the pixels of the resultant raster are not square, but rectangular. Furthermore, I'm not able to produce viewsheds from the interpolated terrain data. I've conducted multiple tests against other national grid squares which work perfectly well.

I've shared the contours for you to have a go at interpolating. Settings are shown below.

If you are able to produce terrain data from my shared shapefile with square pixels, please could you share the result and mention any ideas as to what I might be doing wrong?

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1 Answer 1


i think the reason for this is the NU grid has a lot of sea coverage. The raster that the plugin produces defaults to (I think) a square grid of 300x300 cells.

But because this region has a lot of sea, it's longer in the y direction than the x direction, so having fixed grid results in rectangular cells.

I advise editing the cell sizes in in the dialog to make them the same e.g. 100m x 100m. The plugin will automatically change the resolution for you. That way you should be able to get square (or sufficiently square) cells to keep the ViewShed plugin happy.

  • Agree with Steven, lot of sea coverage in this NU OS Grid tile
    – Mapperz
    Commented Jul 18, 2017 at 14:07
  • Thanks guys, problem averted if I made cell sizes the same. Really great help Steven
    – James B
    Commented Jul 18, 2017 at 15:25

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