[postgis-users] breake lines

[Martin Davis]

If I'm understanding the requirement correctly, the problem with ST_Node is
that it accepts a single geometry and nodes all lines in that geometry.

It sounds like what's required is an ST_Node variant which would accept two
arguments: a target geometry and a noding geometry.  The target geometry
would be noded against the noding geometry, and then returned without
incorporating any additional linework from the noding geometry.

On Tue, Sep 3, 2019 at 10:22 AM Andrea Peri <aperi2007 at gmail.com> wrote:

> Hi,
> I will a chance trying to use the ST_Node.
>
> A.
>
>
>
>
> Il mar 3 set 2019, 19:18 Martin Davis <mtnclimb at gmail.com> ha scritto:
>
>> Have you tried using ST_Split passing each input line and for the second
>> argument a MultiLineString comprised of all lines that it might intersect
>> (obtained via BBOX or ST_Intersects query)?  It seems like that should not
>> create any duplicate linework from the input line.
>>
>> As far as I know there's no other way to do this using current PostGIS
>> functions.   It's an interesting requirement - it sounds like essentially
>> you want to node one layer against another.  There's actually the machinery
>> to do this internally in PostGIS/GEOS, but it's never come up as a
>> requirement before, so has not been exposed as a function.
>>
>> What is your use case?
>>
>> On Tue, Sep 3, 2019 at 9:48 AM <paul.malm at lfv.se> wrote:
>>
>>> If I split lines with another line layer, I will get a lot of duplicaded
>>> line segments since the lines could be intersected several times. It is not
>>> possible to use update on the table when splitting one geomety to two.
>>> I think it must be possible, but I’m not that skilled in SQL and I’ve
>>> not found any examples on the net.
>>>
>>>
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