[postgis-users] Fwd: line direction

George Silva georger.silva at gmail.com
Fri Oct 4 07:12:00 PDT 2013


The direction is always considered from start point to end point. You need
to use these methods to determine everything else.
Em 04/10/2013 08:43, "franco base" <frenk.calza at gmail.com> escreveu:

> Hi Stephen
> How can you explain that the st_offsetcurve make offset according to line
> direction.
>
> For example
> SELECT ST_OffsetCurve (geom, -20)  as geom_off
> FROM table
> WHERE id_arc in (1690,1693)
>
> give me the result that you can see in the attached image rendering in qgis
> (One Direction on the left, the other on the right).
>
> So I have the dirction information inside the arc geometry.
>
>
>
> Thanks
> fb
>
>
> 2013/5/16 Stephen Woodbridge <woodbri at swoodbridge.com>
>
>> How do you define arc direction?
>> If you had a function:
>>
>> select getArcDirection(arc);
>>
>> What would you expect the output to be?
>>
>> In your image, the arc direction is a function of the labeling algorithm
>> in combination with this that of the arc. For example if the label were
>> flipped upside down and written along the underside of the line then the
>> arc direction symbol would have to be reversed. So we can see that it is a
>> function of the label and not just the arc alone.
>>
>> postgis does not do rendering so it can not define that.
>>
>> -Steve
>>
>>
>> On 5/16/2013 11:14 AM, franco base wrote:
>>
>>> I send again message because it was blocked for the attcahed file too big
>>>
>>>
>>> I have a public transport network with an arc for 2 Point(the bus stop).
>>> I'd know without using the points information arc direction like in qgis
>>> (as you can see from the attached imagine with arc_id and direction)
>>>
>>>
>>> 2013/5/14 Nicolas Ribot <nicolas.ribot at gmail.com
>>> <mailto:nicolas.ribot at gmail.**com <nicolas.ribot at gmail.com>>>
>>>
>>>
>>>     Hi,
>>>
>>>     If you want to materialize direction from start to end of line, you
>>>     can use st_startPoint and st_endpoint to determines the right ends.
>>>     What is your use case ?
>>>
>>>     Nicolas
>>>
>>>
>>>     On 14 May 2013 13:49, franco base <frenk.calza at gmail.com
>>>     <mailto:frenk.calza at gmail.com>**> wrote:
>>>
>>>         Hi.
>>>         I know tgis function but doesn't work.
>>>         Myabe my question isn't correct.
>>>         I'd have a binary value according to the arc direction.
>>>         For example, in qgis I can view this information:
>>>         I can see an arrow on my arc according to direction.
>>>         I'd have the same using postgis.
>>>
>>>         Thanks
>>>
>>>
>>>
>>>         2013/5/14 Paolo Corti <pcorti at gmail.com <mailto:pcorti at gmail.com
>>> >>
>>>
>>>
>>>             On Tue, May 14, 2013 at 6:03 PM, franco base
>>>             <frenk.calza at gmail.com <mailto:frenk.calza at gmail.com>**>
>>> wrote:
>>>              > Hi.
>>>              > I have a question for the list.
>>>              >
>>>              > Is there a postgis function to have line direction?
>>>              >
>>>
>>>             http://postgis.refractions.**net/docs/ST_Azimuth.html<http://postgis.refractions.net/docs/ST_Azimuth.html>
>>>
>>>             regards
>>>             p
>>>
>>>             --
>>>             Paolo Corti
>>>             Geospatial software developer
>>>             web: http://www.paolocorti.net
>>>             twitter: @capooti
>>>             skype: capooti
>>>             ______________________________**_________________
>>>             postgis-users mailing list
>>>             postgis-users at lists.osgeo.org
>>>             <mailto:postgis-users at lists.**osgeo.org<postgis-users at lists.osgeo.org>
>>> >
>>>
>>>             http://lists.osgeo.org/cgi-**bin/mailman/listinfo/postgis-**
>>> users <http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users>
>>>
>>>
>>>
>>>         ______________________________**_________________
>>>         postgis-users mailing list
>>>         postgis-users at lists.osgeo.org <mailto:postgis-users at lists.**
>>> osgeo.org <postgis-users at lists.osgeo.org>>
>>>
>>>         http://lists.osgeo.org/cgi-**bin/mailman/listinfo/postgis-**
>>> users <http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users>
>>>
>>>
>>>
>>>     ______________________________**_________________
>>>     postgis-users mailing list
>>>     postgis-users at lists.osgeo.org <mailto:postgis-users at lists.**
>>> osgeo.org <postgis-users at lists.osgeo.org>>
>>>
>>>     http://lists.osgeo.org/cgi-**bin/mailman/listinfo/postgis-**users<http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users>
>>>
>>>
>>>
>>>
>>>
>>> ______________________________**_________________
>>> postgis-users mailing list
>>> postgis-users at lists.osgeo.org
>>> http://lists.osgeo.org/cgi-**bin/mailman/listinfo/postgis-**users<http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users>
>>>
>>>
>> ______________________________**_________________
>> postgis-users mailing list
>> postgis-users at lists.osgeo.org
>> http://lists.osgeo.org/cgi-**bin/mailman/listinfo/postgis-**users<http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users>
>>
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at lists.osgeo.org
> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20131004/b345634a/attachment.html>


More information about the postgis-users mailing list