Robustness issue when validating polygon with nearly parallel edges separated by small distance (self-intersection). Fixed by extended-precision determinant. http://trac.osgeo.org/geos/ticket/588 POLYGON (( -86.3958130146539250 114.3482370100377900, 55.7321237336437390 -44.8146215164960250, 87.9271046586986810 -10.5302909001479530, 87.9271046586986810 -10.5302909001479570, 138.3490775437400700 43.1639042523018260, 64.7285128575111490 156.9678884302379600, -86.3958130146539250 114.3482370100377900)) true