[postgis-users] Extending line segments

Hemant Bist hemantbist at gmail.com
Mon Aug 27 12:47:11 PDT 2018

(I am trying to get permission to send the data).  I have n't tried
st_Straightskeleton. Will try it....

On Mon, Aug 27, 2018 at 11:07 AM, Darafei "Komяpa" Praliaskouski <
me at komzpa.net> wrote:

> Hi!
> First case sounds like ST_Snap.
> For second case, if you are not going to write an extending loop I would
> try to get the polygon after buffering and then try with
> ST_StraightSkeleton and ST_ApproximateMedialAxis.
> Can you share a dataset to play with?
> пн, 27 авг. 2018 г. в 19:34, Hemant Bist <hemantbist at gmail.com>:
>> Hi,
>> Is there something already written that can help me do the following?
>> I need to "extend" the line segments  by a small amount to see if they
>> can be joined.  The use cases are
>> 1) Joining line segments that should be joined in reality but in the data
>> (linstrings) they have a small gap.
>> 2) The vector lines (multiple linestrings) are dashed line representation
>> of real line .e.g. representing a road by dashed line of 4mm dashes with
>> gap of 1 mm between them.
>> I am willing to live with error cases where some line segments are joined
>> when they should not be. The output I need should be
>> I cannot do  st_buffer(st_union(st_buffer( line_geometry, epsilon)),
>> -epsilon) as it turns the lines into area. But visually these areas look
>> close to what I need.
>> The other drawback of st_buffer is that it extends line in all
>> directions, instead of extending line segments in expected directions.
>> Currently  the only  possible "solution" I have in mind is to write
>> something custom to extend the individual line strings and then do st_union.
>> If there are something available in other tools like gdal, grass,  I will
>> be happy to look at them. Currently I don't know of any solutions in other
>> tools as well.
>> Thanks,
>> HB
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> --
> Darafei Praliaskouski
> Support me: http://patreon.com/komzpa
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