[postgis-users] the nearest point of a line from a point

[sylvain dubouis]

Thanks Kevin,
It seems to be the good solution, but I can't execute "st_" functions :

ERROR:  function st_line_locate_point(geometry, geometry) does not exist
HINT:  No function matches the given name and argument types. You may need
to add explicit type casts.

Do you know why? and how I can Install this functions on my
postgresql/postgis server

Sylvain

2008/1/30, Kevin Neufeld <kneufeld at refractions.net>:
>
> See the section on linear referencing (sec. 6.2.7).
> (http://postgis.refractions.net/docs/ch06.html#id2775904)
>
> You'll need to use two methods.
>
> ST_line_locate_point(LineString, Point) returns the percentage along the
> the LineString the closest point will occur.
>
> ST_line_interpolate_point(linestring, location) returns the geometric
> point given a LineString and a percentage along.
>
> SELECT ST_line_interpolate_point(line_geom,
> ST_line_locate_point(line_geom, point_geom))
> FROM ...
>
> Cheers,
> Kevin
>
> sylvain dubouis wrote:
> > hello, I have a point and a line.
> > I'd like to know the nearest point on the line from the  point.
> > but I don't find any function to do this... is there one?
> > thanks for your help.
> > Sylvain
> > ------------------------------------------------------------------------
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