[postgis-users] help with a query

[Jonatan Malaver]

the reason being is that I do a network analysis by running the following
function:
WITH RECURSIVE flow(gid, geom) AS (
    SELECT e.gid, e.geom FROM electric_line e, transformers t WHERE
ST_Distance(t.geom,ST_StartPoint(e.geom)) <= 0.01 AND t.gid=$1
  UNION ALL
    SELECT n.gid, n.geom
    FROM electric_line n, flow f
    WHERE ST_Distance(ST_EndPoint(f.geom),ST_StartPoint(n.geom)) <= 0.01
  )
The problem I have is that some of the lines direction are in reversed. I'm
trying to correct them with referenced to the first line. Otherwise, I will
end up changing hundreds of lines manually.

On Tue, Sep 13, 2016 at 11:12 AM James Keener <jim at jimkeener.com> wrote:

> Depends on what you mean by direction. If you want to grab the start and
> end points (st_startpoint and st_endpoint) and check their x and y (st_x
> and st_y) for some condition (both less at the end?) Then update the record
> with the value of st_reverse.
>
> I guess my other question is why it matters.
>
> Jim
>
> On September 13, 2016 8:31:07 AM EDT, Jonatan Malaver <
> jon.malaver at shrewsburyma.gov> wrote:
>
>> Hello,
>>
>>    I'm trying to come up with a query that would check the direction of a
>> line. If the end point is not the start point of the next line to update
>> the line by reversing that line. Can anyone give me pointers on how to do
>> it?
>>
>> Thanks,
>> Jon
>>
>>
>> postgis-users mailing list
>> postgis-users at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/postgis-users
>>
>>
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.
>
-- 

Thanks,


Jonatan Malaver

Assistant Engineer of Electrical and Cable Operations

Shrewsbury Electric & Cable Operations

100 Maple Avenue

Shrewsbury, MA 01545

Office: (508) 841-8610

Fax: (508) 842-9267

jon.malaver at shrewsburyma.gov
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