Get the Closest Point to a Line: SQL Server 2008 R2

I am trying to find the closest point on a line.

Based on some articles I used the following:


select
@GmPoint.STBuffer(@GmPoint.STDistance(@GmLine)).STIntersection(@GmLine).STStartPoint().ToString()

But the result returns a null.  Any ideas?  I have attached the sql that I am using on SQL 2008 R2
GetClosestPoint.sql
yanci1179Asked:
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ste5anSenior DeveloperCommented:
hmm, shouldn't that not be:

SELECT @GmLine.STIntersection(@GmPoint.STBuffer(@GmPoint.STDistance(@GmLine)));

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?
yanci1179Author Commented:
I tried that, however when you display the ToString()

SELECT @GmLine.STIntersection(@GmPoint.STBuffer(@GmPoint.STDistance(@GmLine))).ToString();

'GEOMETRYCOLLECTION EMPTY' is returned
yanci1179Author Commented:
please see the coordinates that I have attached for example of how it is returning 'GEOMETRYCOLLECTION EMPTY' with SELECT @GmLine.STIntersection(@GmPoint.STBuffer(@GmPoint.STDistance(@GmLine))).ToString();
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ste5anSenior DeveloperCommented:
hmm, when I need to guess: It's due to your weird line definition. E.g. this works:

DECLARE @GmPoint AS GEOMETRY ,
    @GmLine AS GEOMETRY;

SET @GmPoint = GEOMETRY::STGeomFromText('POINT ( 9 11 )', 0);
SET @GmLine = GEOMETRY::STGeomFromText('LINESTRING ( 0 0 null 1, 20 20 null 2 )', 0);

SELECT  @GmLine.STIntersection(@GmPoint.STBuffer(@GmPoint.STDistance(@GmLine))).ToString();

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yanci1179Author Commented:
any ideas on how I can make mine work?  The linestring contains the Measure and by default SQL server does not include the Z value

Thank you for your quick responses!!
ste5anSenior DeveloperCommented:
Well, what kind of "line" is it? Looks like a polygon.
yanci1179Author Commented:
it is a pipeline.  not a polygon.  I attached a picture of it.
Line.GIF
yanci1179Author Commented:
I stripped of the M and Z and only included a portion of the line.  I'm still getting GEOMETRYCOLLECTION EMPTY.  I really appreciate the help, I've been trying to figure this out for a few days and i'm not getting anywhere.

Declare @GmPoint as Geometry
,@GmLine as Geometry

set @GmPoint = geometry::STGeomFromText('POINT (-3456626.2357009738 -167238.147067269)',0)

set @GmLine =
geometry::STGeomFromText('LINESTRING (-839114.95222563 -3451172.56977921, -839114.79576344 -3451167.59279138)',0)

SELECT @GmLine.STIntersection(@GmPoint.STBuffer(@GmPoint.STDistance(@GmLine))).ToString();
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Microsoft SQL Server 2008

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