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I have a data set of water level ranging from -6 m below sea level to +30 meters. But when I use the model example for creating contours from points, the minimum contour value is zero (0). What can be the reason for that?

(I'm using QGIS 2.4.0)

UPDATE: I've tried to run the model in QGIS 2.6 and get this error message. It works fine when running another data set with only possitive values. What is the meaning of the error?

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    Could it be that the interval between contour lines is set to 10? – underdark Nov 21 '14 at 12:53
  • You don't mention how you're creating the contours. If it's with a particular plugin, I believe I've seen in the past that it can't handle negative values and expects all 'elevations' to be positive. A possible workaround is to reset 0/rescale your data (ie, add 10m to all values, run the tool, then adjust the result by subtracting 10m). – Chris W Nov 21 '14 at 20:25
  • I'm using the: Models/Example models/Contour lines from points. Thanks for the tip, I'll try it no other solution will be available. – H.Wiener Nov 23 '14 at 7:25
  • @underdark the interval is set to 1, not 10. – H.Wiener Nov 25 '14 at 8:58
  • This is getting even stranger: I tried to use only part of the points in the data set, choosing them arbitrarily from the map (using select features by polygon) and the the model worked, without contours with negative values. – H.Wiener Nov 25 '14 at 9:50
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I found it! Editting the model in the "Processing modelelr" window so the minimum contour value will include negative values (by default, the minimum level is st to 0).

I still don't know what caused the error message I posted above, but it might just be a problem with the data set, cause the model works fine on other data sets.

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