[OSGeo-Discuss] geospatial algorithm to create area midway boundaries from lines ?

karsten karsten at terragis.net
Fri Mar 6 15:16:36 PST 2020

Hi Pierre,

I mean line segments like e.g. in a road or water GIS layer and they could
be smooth or rather less smooth.
The output I desire should be polygons and not lines. Overall I am looking
for nothing exact here - any approximate interpolation about midway
plus/minus would be fine...


-----Original Message-----
From: Pierre Abbat [mailto:phma at bezitopo.org] 
Sent: Friday, March 06, 2020 14:59
To: discuss at lists.osgeo.org
Cc: karsten
Subject: Re: [OSGeo-Discuss] geospatial algorithm to create area midway
boundaries from lines ?

On Friday, 6 March 2020 17:36:15 EST karsten wrote:
> Hi All,
> a general geospatial question to all:
> I am trying to find out if there is any existing geospatial algorithm 
> (in any open Open Source Geospatial software) that would allow to use 
> a network of lines as a start point and expand those in such a way 
> that I can create new area boundaries for each of the lines "coverage 
> area". What I mean with that is if one could "buffer" the lines out in 
> such a way to create boundaries where any potential buffers would meet 
> at the middle way point between the lines so that in the end I could 
> have an area within that is the starting line. On example could look 
> like this (5 hand drawn lines in red and corresponding colored areas 
> that I would want to create). Note that is exact but to communicate 
> the idea) see 
> http://terra5.terragis.net/sites/html/aeras_for_lines%20copy.png

When you say "lines", do you mean polylines made of line segments, polyarcs,
or polyspirals? If polyarcs, will they generally be smooth? If polyspirals,
will adjacent spiralarcs osculate, just be tangent, or neither?

What sort of lines would the output be? If the input is polyarcs, the output
could contain pieces of hyperbola. If the input is polyspirals, the output
could contain strange indescribable curves. The only curves used as land
boundaries are line segments and circular arcs, so they'd have to be

When a barnacle settles down, its brain disintegrates.
Já não percebe nada, já não percebe nada.

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