Question

OGC valid polygon

  • 3 October 2014
  • 2 replies
  • 3 views

According to OGC SFS (Implementation Standard for Geographic information - Simple feature access - Part 1: Common architecture, version 1.2.1) in a valid polygon "No two Rings in the boundary cross and the Rings in the boundary of a Polygon may intersect at a Point but only as a tangent". So the POLYGON ((0 0, 0 10, 10 10, 10 0, 5 0, 3 3, 5 6, 7 3, 5 0, 0 0)) seems to be OGC valid. Why GeometryValidator treats it as invalid?

2 replies

Userlevel 2
Badge +17
Hi,

 

 

Because the boundary is a twisted and closed LineString; the Polygon does not consist of two Rings - an exterior Ring and an interior Ring.

 

This is valid.

 

POLYGON ((0 0,0 10,10 10,10 0,0 0),(5 0,3 3,5 6,7 3,5 0))

 

 

Takashi
Thank you very much for your quick response!

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