Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/SurfacelineProcessor.cs
===================================================================
diff -u -r3215 -r3349
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/SurfacelineProcessor.cs	(.../SurfacelineProcessor.cs)	(revision 3215)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/SurfacelineProcessor.cs	(.../SurfacelineProcessor.cs)	(revision 3349)
@@ -41,12 +41,16 @@
             dikeTopPolder = surfaceLine.GetSurfaceLinePointByType(CharacteristicPointType.DikeTopAtPolder);
             if (dikeTopPolder == null)
             {
-                throw new Exception(string.Format("Surface line {0} has no Dike Top.", surfaceLine.SurfaceLineId));
+                throw new Exception(string.Format("Surface line {0} has no (unique) Dike Top Polder." + 
+                    " This point may only collide with a traffic load, not with other points.", 
+                    surfaceLine.SurfaceLineId));
             }
             dikeToePolder = surfaceLine.GetSurfaceLinePointByType(CharacteristicPointType.DikeToeAtPolder);
             if (dikeToePolder == null)
             {
-                throw new Exception(string.Format("Surface line {0} has no Dike Toe.", surfaceLine.SurfaceLineId));
+                throw new Exception(string.Format("Surface line {0} has no (unique) Dike Toe Polder." +
+                    " This point may only collide with a traffic load, not with other points.", 
+                    surfaceLine.SurfaceLineId));
             }
         }