[postgis-devel] [PostGIS] #2032: Higher dimension support for ST_ClosestPoint

PostGIS trac at osgeo.org
Fri Oct 5 11:58:22 PDT 2012

#2032: Higher dimension support for ST_ClosestPoint
 Reporter:  strk         |       Owner:  pramsey      
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.1.0
Component:  postgis      |     Version:  2.0.x        
 Keywords:               |  

Comment(by nicklas):

 I'm still around :-)

 First, I guess you mean that today's function returns 'POINT(6 0)' and not
 'POINT(5 0)'.

 Then I think that you suggest the answer 'POINT(5 0 20)' and not 'POINT(5
 20)', right?

 I disagree. ST_ClosestPoint is a 2d function. When I implemented
 ST_3dClosestPOint we had (Regina and me I think) a discussion about if we
 couldn't include the 3d-functionality in the ST_ClosestPoint function. The
 reason we didn't is that you should be aware about what dimensions is used
 in the calculation. You can work on data sets where you are not aware of
 the z-value. And then you will just get very strange 2d-results. If you
 want the z-value in the calculation you should use ST_3DClosestPoint. But
 I see htt ST_3DClosestPoint is handling this situation in a strange way. I
 will open a ticket on that.

Ticket URL: <http://trac.osgeo.org/postgis/ticket/2032#comment:1>
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