[postgis-users] why is this poly invalid?

[Rob Agar]

hi all

Several polygons in our DB are being flagged as invalid by ST_IsValid, 
but I don't really understand why.  Here's one of them as WKT:

"SRID=4326;POLYGON((144.196 -14.2479,144.196 -14.2607,143.736483333333 
-14.2991166666667,143.7384 -14.2987333333333,143.911533333333 
-14.4488166666667,144.037866666667 -14.4488166666667,144.037866666667 
-14.32515,144.119833333333 -14.3589833333333,144.196 -14.2479))"

The documentaion of ST_IsValid could be a little more helpful:

"ST_isvalid(geometry)

     returns true if this geometry is valid."

The poly is self intersecting, but ST_IsSimple returns true - that can't 
be right can it?


(btw in case anyones curious, this one's the boundary of the Princess 
Charlotte Bay coastal area Great Barrier Reef Habitat Protection Zone)

cheers
Rob