I am trying to calculate the area (square feet) of overlap (intersection) of polygons in two shapefiles. Layer 1 has only one polygon. Layer two has many and I know that all of them intersect with the polygon in layer 1. I am trying to calculate the area of the overlap. My code loops through every feature in layer 2 and intersects it with the polygon in Layer 1 using iTopologicalOperator6.IntersectEx. The problem is that the area it calculates is zero for most of the features. It only gets an area for some. As I mentioned, in reality, all polygons intersect. My code is attached. I verified that the loop is getting all features, so it seems the function using the .intersectex method has a problem. Any help is appreciated. Thanks.JustinProtected Overrides Sub OnClick() Try Dim pMap As IMap = My.ArcMap.Document.FocusMap Dim pFLIndex As IFeatureLayer = pMap.Layer(0) Dim pFLSections As IFeatureLayer = pMap.Layer(1) 'get selected features from Sections Dim pFeatSel As IFeatureSelection = pFLSections Dim pSelFeats As ISelectionSet = pFeatSel.SelectionSet 'MsgBox(pSelFeats.Count) 'Get feature from Index Layer Dim pIndexFeature As IFeature = Nothing Dim pCursor As ICursor = pFLIndex.Search(Nothing, False) pIndexFeature = pCursor.NextRow 'MsgBox(pBufFeature.OID & " " & pIndexFeature.OID) 'Loop through features in Buffered sections and calculate overlap sq ft Dim pCur As IFeatureCursor = Nothing Dim pBufFeature As IFeature = Nothing pSelFeats.Search(Nothing, False, pCur) pBufFeature = pCur.NextFeature Do Until pBufFeature Is Nothing Dim dblOverLap As Double = GetArea(pBufFeature, pIndexFeature) 'Calls function pBufFeature.Value(10) = dblOverLap pBufFeature.Store() pBufFeature = pCur.NextFeature Loop My.ArcMap.Document.ActiveView.Refresh() Catch ex As Exception MsgBox(ex.ToString & vbCr & vbCr & ex.Message) End Try My.ArcMap.Application.CurrentTool = Nothing End Sub Private Function GetArea(ByVal FeatureA As IFeature, ByVal FeatureB As IFeature) As Double Dim SourceArea As IArea Dim TargetArea As IArea Dim TopoOp As ITopologicalOperator6 Dim IntersectArea As IArea SourceArea = FeatureA.ShapeCopy 'FeatureA and FeatureB are the polygons to be checked for overlap TargetArea = FeatureB.ShapeCopy TopoOp = TargetArea IntersectArea = TopoOp.IntersectEx(SourceArea, False, ESRI.ArcGIS.Geometry.esriGeometryDimension.esriGeometry2Dimension) GetArea = IntersectArea.Area '/ SourceArea.Area) * 100 'returns the percentage of first polygon which overlaps second polygon SourceArea = Nothing TargetArea = Nothing TopoOp = Nothing IntersectArea = Nothing End Function
