[postgis-devel] [PostGIS] #347: Creating geography type is confusing

PostGIS trac at osgeo.org
Tue Dec 15 06:38:39 PST 2009

#347: Creating geography type is confusing
  Reporter:  robe     |       Owner:  pramsey      
      Type:  defect   |      Status:  new          
  Priority:  medium   |   Milestone:  PostGIS 1.5.0
 Component:  postgis  |     Version:               
Resolution:           |    Keywords:               
Changes (by mcayland):

  * milestone:  PostGIS Future => PostGIS 1.5.0


 I think this was something I touched on before; i.e. a geography without a
 SRID is useless compared to a geometry without a SRID :(

 For example, for a geometry if we have a polygon we can still calculate
 area + length (IMO two of the fundamental properties of a
 linestring/polygon) regardless of whether or not we have a SRID. This
 allows us to use many calculations SRID-less without much of an issue.

 However, for geography the area + length calculations are both dependent
 on the SRID which contains the required information for the curvature of
 the sphere and so without a SRID we can't really do much at all.

 My recommendation would be to currently enforce SRID 4326 on all new
 geographies in trunk so then we always have a reference to calculate these
 two properties. I also think this should be marked as for 1.5.

Ticket URL: <http://trac.osgeo.org/postgis/ticket/347#comment:1>
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