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

PostGIS trac at osgeo.org
Mon Oct 8 11:32:24 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):

 I see the logic Regina, and I guess you are right.

 I just want to point out that the idea of handling undefined z-value as
 ''any'' z-value is quite simple. We don't have to deal with infinite
 polyhedrals in calculations. What we then would do is just make a 2d-
 calculation. That would give us the correct 2d-point. The z-value will be
 the same for both start and end-point of the shortestline in this special
 case of mixed dimension. That is because the 2d geometry will have the
 same shape on every "z-level". Then the shortestline must be horizontal (I

 This would be a true 2.5D behavior. But I agree that putting a z-value on
 a closestpoint or shortestline on a 2d geometry is quite dirty.

 But that will make it harder for Sandro.

 Do we have any function to interpolate the z-value of a point on a line or
 polygon? Or maybe that could be a solution to do what he wants. To do a
 2d-calculation and add the z-value "manually".

Ticket URL: <http://trac.osgeo.org/postgis/ticket/2034#comment:9>
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