[postgis-users] Fwd: line direction

[Stephen Woodbridge]

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>>
>
>     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
>
>             regards
>             p
>
>             --
>             Paolo Corti
>             Geospatial software developer
>             web: http://www.paolocorti.net
>             twitter: @capooti
>             skype: capooti
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