[postgis-users] Creating a linestring from two points

[Juanse]

Per

have you found out if it Is it point or point+1 in every direction?

juanse

----- Original Message -----
From: Per-Olof Norén <pelle at alma.nu>
To: <postgis-users at postgis.refractions.net>
Sent: Friday, November 08, 2002 12:17 PM
Subject: Re: [postgis-users] Creating a linestring from two points


> Hi Dave,
> Sorry for the delay. I managed to figure somthing similar out before you
> could answer it.
>
> Anyway, I used the function x(point1) instead of  xmin though. Isn´t a
> point´s bounding box the point itself?
> or is a point´s bounding box  point+1 unit in every direction? Need
> update using your suggestion?
>
> My query:
> update lank set lank_geom =
> GeometryFromText('LINESTRING(' || x(parent.nod_geom) || ' ' ||
> y(parent.nod_geom)
>  || ',' || x(child.nod_geom) || ' ' || y(child.nod_geom) || ')', 30800)
> from    lank l,
>         nod parent,
>         nod child
> where   lank.parent_nod_id = parent.nod_id
>         and lank.child_nod_id = child.nod_id
>         and l.parent_nod_id = l.parent_nod_id
>
>
> Thanx in advance,
> Per-Olof
>
>
> David Blasby wrote:
>
> >Per-Olof,
> >
> >Unfortunately OGC didnt define any constructors for geometries.  I should
> >really add a few functions to do this - perhaps I'll get some time in the
> >next little while.
> >
> >If you want to construct a line from 2 points, I suggest you build up a
WKT
> >string:
> >
> >Lets look at a simple example - a table with 3 geometry columns called
> >'point1','point2','line'.  The point1 and point2 column have points in
them.
> >
> >The function xmin(geometry) returns the xmin of the geometry's bounding
> >box.  For a point, the points X value is the same as the bounding box's X
> >value.  The '||' operator concatenates 2 strings.
> >
> >UPDATE <table>  SET line =
> >    geometryFromText(
> >       'LINESTRING('|| xmin(point1)||' ' || ymin(point1) ||','||
> >xmin(point2) || ' '||  ymin(point2) || ')'
> >    );
> >
> >dave
> >
> >
> >_______________________________________________
> >postgis-users mailing list
> >postgis-users at postgis.refractions.net
> >http://postgis.refractions.net/mailman/listinfo/postgis-users
> >
> >
>
>
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.408 / Virus Database: 230 - Release Date: 24/10/02