[postgis-devel] [PostGIS] #2034: ST_3DClosestPoint with mixed dimensionality in input values

PostGIS trac at osgeo.org
Sat Oct 6 15:09:45 PDT 2012

#2034: ST_3DClosestPoint with mixed dimensionality in input values
 Reporter:  nicklas      |       Owner:  nicklas      
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.1.0
Component:  postgis      |     Version:  trunk        
 Keywords:               |  

Comment(by nicklas):


 St_3dclosestpoint returns a point on the line, but not the point you want
 since it calculates the 2d point with zero z-value.

 I think it would make sense to handle the z value as undefined instead.
 Than we should find the closest point from any z value. And as I
 understand this that is the value you would like?

 The way to practically do it would be to calculate the 2d closest point
 and interpolate the z value from the vertex before and after the found
 closest point.

 But I think that I disagree that there should be a difference in
 dimentionality depending the order of the arguments. That is because
 st_closestpoint is just the startpoint of st_shortestline.

 What we choose here about how to handle missing z values should also
 affect st_3ddistance.

Ticket URL: <http://trac.osgeo.org/postgis/ticket/2034#comment:6>
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