Hi guysI've got a problem with spatial query. I generate IGeometry igPairLine and compare it a map boundary (IGeometrybag gbBaseMap) using IRelationalOperator. The purpose is checking whether a line is within the map boundary or not. I repeat this process for thousands of thousands lines (literally). But 60 of them were wrong. My code determined they are within the map boundary, but actually not. I don't know why exact same code make such error for certain cases. Does anybody know why? Thank you ISpatialReference sRef; ifMerged = fcMerged.GetFeature(1); IPoint pt = new PointClass(); pt = (IPoint)ifMerged.ShapeCopy; sRef = pt.SpatialReference; IPoint fromPoint = new PointClass(); IPoint toPoint = new PointClass(); fromPoint = pcTempPair.get_Point(0); toPoint = pcTempPair.get_Point(1); IPolyline5 ipPairLine = new PolylineClass(); ipPairLine.ToPoint = toPoint; ipPairLine.FromPoint = fromPoint; ipPairLine.Project(sRef); IGeometry igPairLine = (IGeometry)ipPairLine; IRelationalOperator relOperatore = (IRelationalOperator)gbBaseMap; Boolean contain = relOperatore.Contains(igPairLine);