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Perhaps I am missing some quick pop-up help mechanism, but as a relative newcomer to QGIS (having cut my teeth on ArcGIS 10.1), I am struggling to find reference manuals (i.e. explanations of all parameters/operations) for many of the core commands/plugins. Most of the help seems to be in the form of tutorials, which though some are remarkably well written are not in a useful format when you want to know "what does field X in this dialogue box do?"

Firstly when trying to use the built in Vector -> Geoprocessing -> Buffer tool, what does the "segments to approximate" setting actually mean? Searching the official help pages I could only comes up with the following interesting but rather discursive article:

http://docs.qgis.org/2.2/en/docs/gentle_gis_introduction/vector_spatial_analysis_buffers.html?highlight=buffer

For the Points2one plugin, I've found some quite helpful information already on StackExchange for getting it to do basically what I want, but am surprised that I'm having to scrabble round for such information long after finding the plugin itself. Does anyone know if there is manual page for it? I couldn't find anything from its homepage:

https://launchpad.net/points2one

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On this QGIS wiki page it says that:

Segments to approximate specifies the number of segments to use to approximate a quarter of a circle.

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I was just looking for the same answer myself and while my answer is not 'official', it's based on my interpretation of this Training Manual entry I found:

http://docs.qgis.org/2.2/en/docs/training_manual/answers/answers.html#basic-distance-from-high-schools

I think the above illustrates the buffer segments quite well. My answer is therefore...

The Segments to approximate value is one which determines how many segments are used to draw each section of the buffer. I would guess that playing with values of 1, 2, 3, 5, 10, 20 should give you a good idea of what's going on. A higher value gives a smoother shape. I used 20 and was happy with the resulting buffer I created.

Hope that helps!

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