RES: [postgis-users] Point (x%) on a linestring

[Alex Martins Daher]

Hi!

Thanks for the tips, folks!

I tried to use the line_interpolate_point function, but:

geocoder=# select line_interpolate_point(GeometryFromText('MULTILINESTRING((-51.4933730667105 -29.1662071724963,-51.4933280072013 -29.1666495955688))'),0.5);
ERROR:  line_interpolate_point: 1st arg isnt a line

My geometry is a multilinestring, but if a try to pick the same points as a linestring, I get this
error:
geocoder=# select line_interpolate_point(GeometryFromText('LINESTRING((-51.4933730667105 -29.1662071724963,-51.4933280072013 -29.1666495955688))'),0.5);
ERROR:  couldnt parse object in GEOMETRY

How can I solve this?

Regards,
Alex

> -----Mensagem original-----
> De: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net]Em nome de Paul
> Ramsey
> Enviada em: quinta-feira, 12 de agosto de 2004 19:22
> Para: PostGIS Users Discussion
> Assunto: Re: [postgis-users] Point (x%) on a linestring
> 
> 
> One of the many under documented jewels...
> 
>    line_interpolate_point(geometry,float8)
> 
> Alex Martins Daher wrote:
> 
> > Hi all!
> > 
> > I have a multilinestring like this one:
> > MULTILINESTRING((-51.4933730667105 
> -29.1662071724963,-51.4933280072013 -29.1666495955688))
> > 
> > And I want to know what is the point on the linestring that 
> is x% from the start.
> > For instance, the centroid of that geometry is 50% from the start.
> > 
> > Is there any function that can do that: I pass the geometry 
> anda the percentage and returns
> > the point (geometry) that is x% from the start.
> > 
> > I took a look at that docs but couldn't find anything.
> > 
> > Regards,
> > Alex
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