Thanks for sharing this! Such a great example of collaboration. You are
all amazing.
Date: Wed, 5 Aug 2020 10:09:14 -0700
From: Martin Davis<[email protected]>
To: PostGIS Users Discussion<[email protected]>
Subject: Re: [postgis-users] Find LineString segment index containing
closest point?
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<cak2ens38o2ng2cr2gevm-lm6hgazq1s8eqo3dsj9pbjm2ms...@mail.gmail.com>
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On Wed, Aug 5, 2020 at 9:38 AM Martin Davis<[email protected]> wrote:
Added to the wiki:
https://trac.osgeo.org/postgis/wiki/UsersWikiLinearRefFunctions
It seems a bit awkward to use this as it stands for inserting a vertex in
a line at the closest point. I wonder if the function should also return
the closest point itself? (In fact, I am certain that it should if it is
implemented as a native function, since that additional useful information
costs very little to obtain).
And done... updated the wiki with a new version of the function which
returns the index, distance and computed point on line. Here it is in
action, used for adding a vertex to a line:
WITH data(id, line) AS (VALUES
( 1, 'LINESTRING (0 0, 10 10, 20 20, 30 30)'::geometry )
),
loc AS (
SELECT id, line, index, geom AS pt
FROM data
JOIN LATERAL ST_LineLocateSegment( data.line, 'POINT(15
15.1)'::geometry ) AS lls ON true
)
SELECT id, ST_AsText( ST_AddPoint( line, pt, index ) )
FROM loc;
Note this is probably better done using ST_Snap, but sometimes it's useful
to do things in a more explicit way.
--
------------------------------------------------------------------------
Phil Hurvitz, Research Scientist, CSDE <https://csde.washington.edu/>,
UFL <sites.uw.edu/ufl>
Contact information <http://gis.washington.edu/phurvitz/contact>
Calendar <http://staff.washington.edu/phurvitz/calendar>
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