[postgis-users] Point calculation based on stationary distance

[Simon Greener]

Try something like this:

SELECT ST_AsEWKT(ST_PointN(ST_OffsetCurve(line1,5),ST_NPoints(line1))) as offset_point,
        ST_AsEWKT(ST_PointN(line1,ST_NPoints(line1)))                   as point_10m_on_line
   FROM (SELECT ST_GeometryN(ST_Split(the_line,
                                      ST_Line_Interpolate_Point(the_line,1.0/ST_Length(the_line))),
                             1) as line1
           FROM (SELECT ST_GeomFromEWKT('LINESTRING(25 50, 100 125, 150 190)') as the_line ) as a
        ) as f;

regards
Simon
On Sat, 19 May 2012 17:34:07 +1000, Uroš Bernik <uros.bernik at siol.net> wrote:

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> Hello,
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> A question: I have a linestring (polyline) for which i would like to calculate a point which is located on the polyline but a specific distance from the end or beggining of the polyline. Once this point is calculated >i would then like to calculate 2 points on both sides of the linestring, which are perpendicular to the line like this:
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> [Description: cid:image001.jpg at 01CD3522.C7638240]
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> Any idea how to do this? I didnt notice any function within postgis that deal with stationary distances which is what im looking for probably. Thanks for any advice!
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-- 
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