[postgis-users] line_interpolate_point

[strk at refractions.net]

line_locate_point() search for the "closest" point on the line.
Check distance between line_interpolate_point and your actual point.
They're likely not the same.
You should feed line_interpolate_point() return to your intersection,
without using WKT representation,which would slightly shift geoms.
--strk;


On Mon, Sep 18, 2006 at 12:00:19PM +0200, mj wrote:
> Hello,
> the result of an line_interpolate_point(line_locate_point(....)), fails 
> on intersects() function, between
> the result of the interpolation and the line.
> 
> How I can obtain a point that is guaranted to intersects the line, with 
> interpolation?
> 
> Thanks
> 
> Example data:
> 
> --Interpolation
> select AsEWKT(line_interpolate_point(GeomFromText('LINESTRING(692592.1 
> 135072.3,692574.4 135071.6,
> 692531.7 135066.2,692503.5 135057.3)',-1),
> line_locate_point(GeomFromText('LINESTRING(692592.1 135072.3,692574.4 
> 135071.6,
> 692531.7 135066.2,692503.5 135057.3)',-1),
> GeomFromText('POINT(692526.54112091 135065.87825639)',-1)) ) )
> 
> --Check for itnersections
> select intersects(GeomFromText('LINESTRING(692592.1 135072.3,692574.4 
> 135071.6,
> 692531.7 135066.2,692503.5 135057.3)',-1),
> GeomFromText('POINT(692526.916080715 135064.690181502)',-1))
> 
> result -> false;
> 
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