v.distance.buffer does not create proper buffers with flat endcaps

Question

I try to create flat end buffers for each of my line segments in QGIS (with Grass-algorithm v.buffer.distance).

If I use the tool with straight lines there is no problem creating the flat end buffer polygons but if i use my digitized line which is not straight i end up with strange artefacts as you can see in this screenshot: ( The left side buffers are the ones created by the tool and the ones on the right side are just there to demonstrate the way it roughly should look like.)

Is there a way I can prevent the flat-end-buffer-tool from creating these strange buffer polygons?

Edit1:

I tried the v.parallel-Tool but this also creates strange artefacts:

Result of v.buffer.distance:

Result of v.parallel:

Kazuhito · Answer 1 · 2017-03-06T06:02:05.127

1

As you have described already, you have segmented line features... that's why.

Merge your digitized lines into single line then try again.

[EDIT] Workflow the image below was created:

Merge the segments into single line.
Activate v.parallel and set Offsets =(same offset to both major and minor axis), set Side =(both), and check (Create buffer-like parallel lines).
After v.parallel creates lines, manually digitize to create polygons, using snapping to the line layer.

Not v.buffer answer, and I am not sure you'll like digitizing manually.... anyway.

edited Mar 06 '17 at 06:02

answered Mar 06 '17 at 00:43

Kazuhito

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Thanks but I need a flat end buffer polygon for every segment of my line, not for the hole line – Thomas B Mar 06 '17 at 04:54
@markgraeflerland Sorry I misunderstood your requirement. Are you thinking something like the additional image? – Kazuhito Mar 06 '17 at 05:47
yes,a flat end buffer for every line segment (I dissolved the line by attributes before) – Thomas B Mar 06 '17 at 05:49
I tried v.parallel but this also creates strange artefacts (see edited question above) – Thomas B Mar 06 '17 at 06:58
@markgraeflerland It looks as though you have selected Make outside corners round. Otherwise it looks good. – Kazuhito Mar 06 '17 at 07:02
If I don't select "Make outside corners round" the parallel lines go totally crazy: https://i.stack.imgur.com/GqOTD.png – Thomas B Mar 06 '17 at 07:08
@markgraeflerland Ummm... yes, it is really awful. No idea of what is happening. – Kazuhito Mar 06 '17 at 07:11
Did you end up figuring this out? I have a similar problem... – user32882 Jul 25 '18 at 06:44

v.distance.buffer does not create proper buffers with flat endcaps

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