[postgis-devel] [PostGIS] #231: New distance-calculations proposal

[PostGIS]

#231: New distance-calculations proposal
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  Reporter:  nicklas      |       Owner:  robe         
      Type:  enhancement  |      Status:  assigned     
  Priority:  medium       |   Milestone:  postgis 1.5.0
 Component:  postgis      |     Version:               
Resolution:               |    Keywords:               
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Comment (by nicklas):

 For the record

 {{{
 ST_ClosestPoint(A,B) => SELECT ST_StartPoint(ST_ShortestLine(A,B));
 ST_FurthestPoint(A,B) => SELECT ST_StartPoint(ST_LongestLine(A,B));
 }}}
 above should be
 {{{
 ST_ClosestPoint(A,B) => SELECT ST_EndPoint(ST_ShortestLine(A,B));
 ST_FurthestPoint(A,B) => SELECT ST_EndPoint(ST_LongestLine(A,B));
 }}}
 if I don't missunderstand you Regina.[[BR]]

 Then you get the closest and most far point in geometry B, from geometry
 A[[BR]]
 from the today definition of shortest and longest line.
 [[BR]]
 Here might be a small problem in what people ecpect. closest point is no
 problem I thing but frthest point might give the impression that it is the
 point most fas from geometry A but it is the most far away point in
 geometry B from the most far away point in geometry A.

 Maybe it is only closest point that is of real interest? To avoid
 missunderstanding.

 Or maybe closest and furthest points should be the beginning and the end
 of shortest line instead? like this:
 {{{
 ST_ClosestPoint(A,B) => SELECT ST_StartPoint(ST_ShortestLine(A,B));
 ST_FurthestPoint(A,B) => SELECT ST_EndPoint(ST_ShortestLine(A,B));
 }}}
 Then closestPoint is a point on geometry A and furthestPoint is a point on
 geometry B.
 [[BR]]


 ???

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/231#comment:26>
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