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I am looking for a possibility to create a second line in a given distance to an existing line. The existing line is curved, so simply create parallel line segments with CAD tools will not work.

Any solutions? Thanks in advance.

Addendum:

I mapped vegetation types in the surroundings of small streams. The vegetation types have to be displayed on the map as stream-accompanying lines, prallel to the water bodies. So the second line (vegetation) has different properties compared to the first line (stream) and is a feauture of a different shape file.

The solution I found yet is to create buffers around the streams and to trace their borders, but it is time-consuming.

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Do you want to (1) visually represent one line feature with two lines offset from each other? (cartographic representation, so it's two lines when you look at the map but only one line in the data), or do you want to (2) create a second line feature having different coordinates and possibly different properties? (data representation). Can you provide more details on the use case: what are you trying to do? –  andytilia Sep 14 '12 at 14:17
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It's not clear from your explanation why buffering does not give you the results you want. If you want the boundary lines of the buffers, then use the "Polygon to Lines" tool in the Vector->Geprocessing menu. –  Micha Sep 15 '12 at 10:33
    
@Micha has it. I think that's your answer. –  andytilia Sep 15 '12 at 12:03
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1 Answer

up vote 4 down vote accepted

Not sure if I fully understand the question, but GRASS v.parallel from the amazing Sextante toolbox will create parallel lines (in a new shapefile). You'll probably want to use the same value for the offset along the major axis as you use for the offset along the minor axis.

N.

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