ITopologicalOperator.ConstructUnion Problem

Question

Hello all,

I have been using Contructunion method to merge multiple polygons from source to target feature class . Recently I noticed that the target features are not aligning with source . They are off by 0.19-0.9 ft . Below is my code . Can anybody give me an idea why this could be happening ?

qfeature = qFeaturecursor.NextFeature();
 while (qfeature != null)
    {
  if (qfeature.Shape.GeometryType == esriGeometryType.esriGeometryPolygon)
  {
  pGeoCollection.AddGeometry(qfeature.ShapeCopy);
  }

if ((pGeoCollection.GeometryCount > 0) && (bgeometryerror == false))
 {
  IPolygon pPolygon = null;
  unionedPolygon.ConstructUnion(pGeoBag as IEnumGeometry);
  pPolygon = (IPolygon)unionedPolygon;
 }

VikramS · Answer

Do the source and target FeatureClasses have different XY precision? Maybe you are getting some sort of truncation of the xth decimal place? Especially if you are going from a Shapefile to say a high precision geodatabase featureclass?

Hello Duncan ,

Source and Target are coming from ArcSDE .

Hornbydd · Answer

Do the source and target FeatureClasses have different XY precision? Maybe you are getting some sort of truncation of the xth decimal place? Especially if you are going from a Shapefile to say a high precision geodatabase featureclass?