Index: DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/GeometryPointString.cs
===================================================================
diff -u -r6747 -r7071
--- DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/GeometryPointString.cs	(.../GeometryPointString.cs)	(revision 6747)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/GeometryPointString.cs	(.../GeometryPointString.cs)	(revision 7071)
@@ -78,7 +78,7 @@
     /// <summary>
     /// Matching distance where a point within this range is considered on the same point.
     /// </summary>
-    private const double epsilon = GeometryConstants.Accuracy;
+    private const double epsilon = GeometryConstants.Tolerance;
 
     /// <summary>  
     /// The calculate points as protected field (to be able to prevent recursive calls to Points)
@@ -382,9 +382,8 @@
     /// <returns></returns>
     public Point2D DeterminePointAt(double x, double z)
     {
-        return points.FirstOrDefault(
-            point => point.X.AlmostEquals(x, GeometryPoint.Precision) &&
-                     point.Z.AlmostEquals(z, GeometryPoint.Precision));
+        return points.FirstOrDefault(point => point.X.AlmostEquals(x, GeometryPoint.Precision) &&
+                                              point.Z.AlmostEquals(z, GeometryPoint.Precision));
     }
 
     /// <summary>
@@ -493,6 +492,12 @@
         return RelativeXzPosition.OnGeometricLine;
     }
 
+    public RelativeXzPosition PositionXzOfPointRelatedToExtrapolatedLine(Point2D point,
+                                                                         ExtraPolationMode extraPolationMode = ExtraPolationMode.Beyond)
+    {
+        return IsPointConsideredBeyondLine(point, extraPolationMode) ? RelativeXzPosition.BeyondGeometricLine : DeterminePositionWithRespectToExtrapolatedLine(point, extraPolationMode);
+    }
+
     /// <summary>
     /// Gets the surrounding rectangle around the geometry point string
     /// </summary>
@@ -552,12 +557,6 @@
         return intersectionPointsWithLine;
     }
 
-    public RelativeXzPosition PositionXzOfPointRelatedToExtrapolatedLine(Point2D point,
-                                                                          ExtraPolationMode extraPolationMode = ExtraPolationMode.Beyond)
-    {
-        return IsPointConsideredBeyondLine(point, extraPolationMode) ? RelativeXzPosition.BeyondGeometricLine : DeterminePositionWithRespectToExtrapolatedLine(point, extraPolationMode);
-    }
-
     private bool IsPointConsideredBeyondLine(Point2D point, ExtraPolationMode extraPolationMode)
     {
         if (Points.Count == 0)
@@ -578,11 +577,18 @@
     {
         double xToEvaluate = DetermineXToEvaluate(point, extraPolationMode);
         double zAtX = GetZatX(xToEvaluate);
-        if (Math.Abs(point.Z - zAtX) < 0.001)
+        if (Math.Abs(point.Z - zAtX) < GeometryConstants.Accuracy)
         {
             return RelativeXzPosition.OnGeometricLine;
         }
 
+        // Look also at the horizontal distance between the point and the line in case of steep line
+        double xAtZ = GetXatZ(point.Z, point.X - 2 * GeometryConstants.Accuracy);
+        if (Math.Abs(point.X - xAtZ) < GeometryConstants.Accuracy)
+        {
+            return RelativeXzPosition.OnGeometricLine;
+        }
+
         return point.Z <= zAtX ? RelativeXzPosition.BelowGeometricLine : RelativeXzPosition.AboveGeometricLine;
     }
 
@@ -733,7 +739,7 @@
                     result.Add((1.0 - fraction) * current.Z + fraction * next.Z);
                 }
 
-                // if both ofsets are negative the waterline goes back
+                // if both offsets are negative, the waterline goes back
                 if ((leftOffset < 0) && (rightOffset < 0))
                 {
                     double fraction = rightOffset / (rightOffset + leftOffset);
@@ -808,9 +814,8 @@
 
     private static bool NoPointSameXzLocation(IEnumerable<Point2D> collection, Point2D point)
     {
-        return !collection.Any(
-                   p => Math.Abs(p.X - point.X) < GeometryConstants.Accuracy &&
-                        Math.Abs(p.Z - point.Z) < GeometryConstants.Accuracy);
+        return !collection.Any(p => Math.Abs(p.X - point.X) < GeometryConstants.Accuracy &&
+                                    Math.Abs(p.Z - point.Z) < GeometryConstants.Accuracy);
     }
 
     private List<Point2D> IntersectWithPointsListCore(IList<Point2D> list, bool closePointString)