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I am trying to do a bathymetric map for a lake using QGIS. However, I see no option to impose a mask so interpolation does not extending beyond the boundaries of my lake. I have traced around the lake (polygon) to which I would like to restrict the interpolation. Is there a "set mask" function in QGIS that would restrict all subsequent calaculations? I know how to convert the polgon to raster if needed. I have cliped to the lake boundaries but it still runs over. Do I need to go to GRASS to do this? Using version 1.8 on Windows 7.

Thanks

Alyre

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You can use

enter image description here

  • Thanks. The images illustrate the problem. The TIN gets applied to the whole region. Since the interpolation depends on neighboring values this results in inaccuracy especially at the boundary between the lake and the shoreline. So cutting out the lake region after interpolation of the region will not work. GDAL Warp will provide a means to generate a mask but I don't see how it can be activated with Quantum GIS, I also hope to take my students through these steps and the later is somewhat complicated. Looks like GRASS will have to be the way to go. – user21979 Sep 26 '13 at 13:16
  • yes you must use GRASS GIS for that – gene Sep 26 '13 at 15:59

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