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Using QGIS (by now I have the 2.4 version) I would like to set some parameter (I don't know if such exists) that would impose a definite or maximal distance between nodes when digitizing a polyline or polygon.

I need this to respect a minimal grain in the mapped features which I have to bring out.

For example I would like to set a digitizing distance between nodes of -let say- 15 m, that is, when digitizing, I will be forced to make a node either all 15 meters (not more, not less) or at least all 15 m (i.e. within few to max. 15 m).

I searched in QGIS menu : Settings > Options > Digitizing, and also in plugins but could not find anything that seems appropriate to me. But maybe I overlooked something ?

Thanks a lot for any help.

NB : I don't want to calculate nor find out distances ! I want to set them.

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  • Isn't this contradicting: "15 meters (not more, not less) or at least all 15 m (i.e. within few to max. 15 m)"?
    – underdark
    Commented Aug 5, 2014 at 19:07
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    This should happen while you digitize and post-process densify will not make you happy? That could be done with ogr2ogr by using the -segmentize option gdal.org/ogr2ogr.html. Perhaps you should try OpenJUMP and use the Draw constrained linestring tool after activating and setting the segment length steps to 15 m in the settings.
    – user30184
    Commented Aug 5, 2014 at 20:14
  • @underdark : you may see it as contradicting, but I meant it as an alternative to widen a little the potential solutions to my needs : I would like to set a parameter that allow me to respect the needed grain for the mapped features. In the first alternative (no more no less than 15 m) it would be a bit restrictive but still scope my needs if such possibility exist. I would indeed prefer the second alternative (few to max. 15m) which scopes with my need and would leave me some flexibility.
    – flo64
    Commented Aug 5, 2014 at 21:37
  • @user30184 : The second option you mention sounds like it would be what I look for, but I would by far prefer to stay by QGIS as I don't know OpenJump. For the first proposition you suggest, I don't know what is post-process densify. Is that, e.g., if I had one 48m-long segment, it would split it into three 15m-long and one 3m-long segments or something like that ? If it is so, it would "result as" but it looks like a tricky solution and using it would not be honest to scope with my need.
    – flo64
    Commented Aug 5, 2014 at 21:47
  • With post-process I meant that you could digitize the whole job ready with QGIS, save the result into shapefile and finally add more vertices by converting the result into a new shapefile with ogr2ogr by using the -segmentize switch. Your 48 m example is right and this system would not prevent digitizing less than 15 m long lines. You can try OpenJUMP and if the tool feels right for you make a feature request about implementing similar for QGIS.
    – user30184
    Commented Aug 6, 2014 at 4:34

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