[postgis-users] Make a shorter line from a given line

[Daniel Grum]

nicklas.aven at jordogskog.no schrieb:
> look at st_scale
> http://www.postgis.org/documentation/manual-1.4.1SVN/ST_Scale.html
>  
> or maybe st_transscale
> http://www.postgis.org/documentation/manual-1.4.1SVN/ST_TransScale.html
> /Nicklas
>  
>  
>
> 2009-09-08 Daniel Grum wrote:
>
> Hy,
> >
> >I want to make a new line from a given line -->both geometry types are
> >MULTININESTRING
> >
> >Every step the new line should be "x meters" shorter than the original.
> >
> >I get the length of the line, f.e. 5000 meters (length(the_geom)) and
> >after the step the new Line should be only 4000 meters.
> >
> >I have a idea but it isn't ready:
> >
> >UPDATE table
> >SET the_geom = (SELECT MakeLine(StartPoint(line.the_geom),
> >EndPoint(line_merge(line.the_geom)))
> > FROM public.table line
> > ORDER BY line.gid);
> >
> >But in if I do so I have no chance to say that the new line has to be
> >100meters shorter than the original line.
> >
> >Are there any ideas how I can solve this problem?
> >
> >Thanks,
> >--Daniel
> >_______________________________________________
> >postgis-users mailing list
> >postgis-users at postgis.refractions.net
> >http://postgis.refractions.net/mailman/listinfo/postgis-users
> >
> >
That is not what I'm searching for.

Becaus the line lies somewhere in the 2D space and the end point of the 
line anytime will be the same in my case...only the starting point 
should be changed.
And it should be changed automaticly, step by step, and the new starting 
point hvave to be on the old line/route-->like a route in a map and 
every time step the route will be shorter, because the unit has solved x 
meters.

Do you know what I mean?

Scale and TransScale isn't the right finction I think.
--daniel