Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/Deltares.LayerOnSlopeTool.LayerCreator.Tests.csproj
===================================================================
diff -u -r3183 -r3185
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/Deltares.LayerOnSlopeTool.LayerCreator.Tests.csproj	(.../Deltares.LayerOnSlopeTool.LayerCreator.Tests.csproj)	(revision 3183)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/Deltares.LayerOnSlopeTool.LayerCreator.Tests.csproj	(.../Deltares.LayerOnSlopeTool.LayerCreator.Tests.csproj)	(revision 3185)
@@ -30,6 +30,7 @@
   <ItemGroup>
     <Compile Include="LayerCreatorTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="SurfacelineProcessorTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="..\Copying.AGPL.licenseheader">
Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/LayerCreator.cs
===================================================================
diff -u -r3183 -r3185
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/LayerCreator.cs	(.../LayerCreator.cs)	(revision 3183)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/LayerCreator.cs	(.../LayerCreator.cs)	(revision 3185)
@@ -201,7 +201,8 @@
 
         private SurfaceLine DetermineSurfaceLineForGivenLayerData(SurfaceLine originalSurfaceLine, double layerThickness)
         {
-            return originalSurfaceLine.CreateLoweredSurfaceLineForGivenLayerThickness(layerThickness);
+            var surfacelineProcessor = new SurfacelineProcessor(originalSurfaceLine);
+            return surfacelineProcessor.CreateLoweredSurfaceLine(layerThickness);
         }
     }
 
Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/SurfacelineProcessorTests.cs
===================================================================
diff -u
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/SurfacelineProcessorTests.cs	(revision 0)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/SurfacelineProcessorTests.cs	(revision 3185)
@@ -0,0 +1,253 @@
+// Copyright (C) Stichting Deltares 2020. All rights reserved.
+//
+// This file is part of the Dam Engine.
+//
+// The Dam Engine is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using Deltares.LayerOnSlopeTool.Data;
+using NUnit.Framework;
+
+namespace Deltares.LayerOnSlopeTool.LayerCreator.Tests
+{
+    [TestFixture]
+    public class SurfacelineProcessorTests
+    {
+        private const double tolerance = 0.001;
+
+        [Test]
+        public void TestDetermineLoweredSurfaceLineForGivenLayerThickness()
+        {
+            var originalSurfaceLine = CreateSimpleStraightSurfaceLine();
+            var surfacelineProcessor = new SurfacelineProcessor(originalSurfaceLine);
+            var loweredSurfaceLine = surfacelineProcessor.CreateLoweredSurfaceLine(1);
+            Assert.AreEqual(11, loweredSurfaceLine.SurfaceLinePoints.Count);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].ZCoordinate, tolerance);
+            Assert.AreEqual(5, loweredSurfaceLine.SurfaceLinePoints[1].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[1].ZCoordinate, tolerance);
+            Assert.AreEqual(10, loweredSurfaceLine.SurfaceLinePoints[2].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[2].ZCoordinate, tolerance);
+            Assert.AreEqual(12, loweredSurfaceLine.SurfaceLinePoints[3].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[3].ZCoordinate, tolerance);
+            Assert.AreEqual(14, loweredSurfaceLine.SurfaceLinePoints[4].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[4].ZCoordinate, tolerance);
+            Assert.AreEqual(14.01, loweredSurfaceLine.SurfaceLinePoints[5].XCoordinate, tolerance);
+            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[5].ZCoordinate, tolerance);
+            Assert.AreEqual(15, loweredSurfaceLine.SurfaceLinePoints[6].XCoordinate, tolerance);
+            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[6].ZCoordinate, tolerance);
+            Assert.AreEqual(15.99, loweredSurfaceLine.SurfaceLinePoints[7].XCoordinate, tolerance);
+            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[7].ZCoordinate, tolerance);
+            Assert.AreEqual(16, loweredSurfaceLine.SurfaceLinePoints[8].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[8].ZCoordinate, tolerance);
+            Assert.AreEqual(22, loweredSurfaceLine.SurfaceLinePoints[9].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[9].ZCoordinate, tolerance);
+            Assert.AreEqual(30, loweredSurfaceLine.SurfaceLinePoints[10].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[10].ZCoordinate, tolerance);
+
+        }
+
+        [Test]
+        public void TestDetermineLoweredSurfaceLineForGivenLayerThicknessWithAckwardPoints()
+        {
+            var originalSurfaceLine = CreateSimpleStraightSurfaceLineWithAckwardPoints();
+            var surfacelineProcessor = new SurfacelineProcessor(originalSurfaceLine);
+            var loweredSurfaceLine = surfacelineProcessor.CreateLoweredSurfaceLine(1);
+            Assert.AreEqual(11, loweredSurfaceLine.SurfaceLinePoints.Count);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].ZCoordinate, tolerance);
+            Assert.AreEqual(5, loweredSurfaceLine.SurfaceLinePoints[1].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[1].ZCoordinate, tolerance);
+            Assert.AreEqual(10, loweredSurfaceLine.SurfaceLinePoints[2].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[2].ZCoordinate, tolerance);
+            Assert.AreEqual(12, loweredSurfaceLine.SurfaceLinePoints[3].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[3].ZCoordinate, tolerance);
+            Assert.AreEqual(14, loweredSurfaceLine.SurfaceLinePoints[4].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[4].ZCoordinate, tolerance);
+            Assert.AreEqual(14.01, loweredSurfaceLine.SurfaceLinePoints[5].XCoordinate, tolerance);
+            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[5].ZCoordinate, tolerance);
+            Assert.AreEqual(15.5, loweredSurfaceLine.SurfaceLinePoints[6].XCoordinate, tolerance);
+            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[6].ZCoordinate, tolerance);
+            Assert.AreEqual(15.99, loweredSurfaceLine.SurfaceLinePoints[7].XCoordinate, tolerance);
+            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[7].ZCoordinate, tolerance);
+            Assert.AreEqual(16, loweredSurfaceLine.SurfaceLinePoints[8].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[8].ZCoordinate, tolerance);
+            Assert.AreEqual(22, loweredSurfaceLine.SurfaceLinePoints[9].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[9].ZCoordinate, tolerance);
+            Assert.AreEqual(30, loweredSurfaceLine.SurfaceLinePoints[10].XCoordinate, tolerance);
+            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[10].ZCoordinate, tolerance);
+
+        }
+
+        private SurfaceLine CreateSimpleStraightSurfaceLine()
+        {
+            var surfaceLine = new SurfaceLine();
+            surfaceLine.SurfaceLineId = "SimpleStraightSurfaceLine";
+            var point = new SurfaceLinePoint
+            {
+                XCoordinate = 0,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.SurfaceLevelOutside
+            };
+            surfaceLine.SurfaceLinePoints.Add(point);
+            var pointA = new SurfaceLinePoint
+            {
+                XCoordinate = 5,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(pointA);
+            var point1 = new SurfaceLinePoint
+            {
+                XCoordinate = 10,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeToeAtRiver
+            };
+            surfaceLine.SurfaceLinePoints.Add(point1);
+            var point2 = new SurfaceLinePoint
+            {
+                XCoordinate = 12,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeTopAtRiver
+            };
+            surfaceLine.SurfaceLinePoints.Add(point2);
+            var point3 = new SurfaceLinePoint
+            {
+                XCoordinate = 14,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeTopAtPolder
+            };
+            surfaceLine.SurfaceLinePoints.Add(point3);
+            var point3A = new SurfaceLinePoint
+            {
+                XCoordinate = 15,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(point3A);
+            var point4 = new SurfaceLinePoint
+            {
+                XCoordinate = 16,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeToeAtPolder
+            };
+            surfaceLine.SurfaceLinePoints.Add(point4);
+            var point4A = new SurfaceLinePoint
+            {
+                XCoordinate = 22,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(point4A);
+            var point5 = new SurfaceLinePoint
+            {
+                XCoordinate = 30,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.SurfaceLevelInside
+            };
+            surfaceLine.SurfaceLinePoints.Add(point5);
+            return surfaceLine;
+        }
+
+        private SurfaceLine CreateSimpleStraightSurfaceLineWithAckwardPoints()
+        {
+            var surfaceLine = new SurfaceLine();
+            surfaceLine.SurfaceLineId = "SimpleStraightSurfaceLine";
+            var point = new SurfaceLinePoint
+            {
+                XCoordinate = 0,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.SurfaceLevelOutside
+            };
+            surfaceLine.SurfaceLinePoints.Add(point);
+            var pointA = new SurfaceLinePoint
+            {
+                XCoordinate = 5,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(pointA);
+            var point1 = new SurfaceLinePoint
+            {
+                XCoordinate = 10,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeToeAtRiver
+            };
+            surfaceLine.SurfaceLinePoints.Add(point1);
+            var point2 = new SurfaceLinePoint
+            {
+                XCoordinate = 12,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeTopAtRiver
+            };
+            surfaceLine.SurfaceLinePoints.Add(point2);
+            var point3 = new SurfaceLinePoint
+            {
+                XCoordinate = 14,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeTopAtPolder
+            };
+            surfaceLine.SurfaceLinePoints.Add(point3);
+            var point3A = new SurfaceLinePoint
+            {
+                // is less than 0.01 meter beyond the point that is to be lowered with offset of 0.01 m. So this point should NOT be found in the lowered line
+                XCoordinate = 14.001,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(point3A);
+            var point3B = new SurfaceLinePoint
+            {
+                // make this 15.5 instead of 15 to be different from ordinary SimpleStraightSurfaceLine.
+                XCoordinate = 15.5,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(point3B);
+            var point3C = new SurfaceLinePoint
+            {
+                // is less than 0.01 meter in front off the point that is to be lowered with offset of -0.01 m. So this point should NOT be found in the lowered line
+                XCoordinate = 15.999,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(point3C);
+            var point4 = new SurfaceLinePoint
+            {
+                XCoordinate = 16,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.DikeToeAtPolder
+            };
+            surfaceLine.SurfaceLinePoints.Add(point4);
+            var point4A = new SurfaceLinePoint
+            {
+                XCoordinate = 22,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.None
+            };
+            surfaceLine.SurfaceLinePoints.Add(point4A);
+            var point5 = new SurfaceLinePoint
+            {
+                XCoordinate = 30,
+                ZCoordinate = 0,
+                PointType = CharacteristicPointType.SurfaceLevelInside
+            };
+            surfaceLine.SurfaceLinePoints.Add(point5);
+            return surfaceLine;
+        }
+    }
+}
\ No newline at end of file
Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/Deltares.LayerOnSlopeTool.LayerCreator.csproj
===================================================================
diff -u -r3183 -r3185
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/Deltares.LayerOnSlopeTool.LayerCreator.csproj	(.../Deltares.LayerOnSlopeTool.LayerCreator.csproj)	(revision 3183)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/Deltares.LayerOnSlopeTool.LayerCreator.csproj	(.../Deltares.LayerOnSlopeTool.LayerCreator.csproj)	(revision 3185)
@@ -46,6 +46,7 @@
   <ItemGroup>
     <Compile Include="LayerCreator.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="SurfacelineProcessor.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Copying.AGPL.licenseheader" />
Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.Data/SurfaceLine.cs
===================================================================
diff -u -r3184 -r3185
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.Data/SurfaceLine.cs	(.../SurfaceLine.cs)	(revision 3184)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.Data/SurfaceLine.cs	(.../SurfaceLine.cs)	(revision 3185)
@@ -19,7 +19,6 @@
 // Stichting Deltares and remain full property of Stichting Deltares at all times.
 // All rights reserved.
 
-using System;
 using System.Collections.Generic;
 
 namespace Deltares.LayerOnSlopeTool.Data
@@ -88,92 +87,5 @@
             return surfaceLinePoint;
         }
 
-        /// <summary>
-        /// Creates the lowered surface line for given layer thickness.
-        /// </summary>
-        /// <param name="layerThickness">The layer thickness.</param>
-        /// <returns></returns>
-        public SurfaceLine CreateLoweredSurfaceLineForGivenLayerThickness(double layerThickness)
-        {
-            const double tolerance = 1e-4;
-            const double horizontalOffset = 0.01;
-            var loweredSurfaceLine = new SurfaceLine();
-            var dikeTopPolder = GetSurfaceLinePointByType(CharacteristicPointType.DikeTopAtPolder);
-            var dikeToePolder = GetSurfaceLinePointByType(CharacteristicPointType.DikeToeAtPolder);
-            foreach (var point in SurfaceLinePoints)
-            {
-                if (point.XCoordinate <= dikeTopPolder.XCoordinate)
-                {
-                    HandlePointsUpToAndIncludingDikeTopPolder(layerThickness, point, loweredSurfaceLine, dikeTopPolder, tolerance, horizontalOffset);
-                }
-                else
-                {
-                    // Handle all points between dike top polder and dike toe polder (taking into account the horizontal offset).
-                    if (point.XCoordinate > dikeTopPolder.XCoordinate + horizontalOffset && point.XCoordinate < dikeToePolder.XCoordinate - horizontalOffset)
-                    {
-                        var newPointLowered = new SurfaceLinePoint
-                        {
-                            XCoordinate = point.XCoordinate,
-                            ZCoordinate = point.ZCoordinate - layerThickness,
-                            PointType = point.PointType
-                        };
-                        loweredSurfaceLine.SurfaceLinePoints.Add(newPointLowered);
-                    }
-                    else
-                    {
-                        HandlePointsAtDikeToePolderAndBeyond(layerThickness, point, dikeToePolder, tolerance, horizontalOffset, loweredSurfaceLine);
-                    }
-                }
-            }
-            return loweredSurfaceLine;
-        }
-
-        private static void HandlePointsAtDikeToePolderAndBeyond(double layerThickness, SurfaceLinePoint point,
-            SurfaceLinePoint dikeToePolder, double tolerance, double horizontalOffset, SurfaceLine loweredSurfaceLine)
-        {
-            if (Math.Abs(point.XCoordinate - dikeToePolder.XCoordinate) < tolerance)
-            {
-                var newPointAtDikeToe = new SurfaceLinePoint
-                {
-                    XCoordinate = point.XCoordinate - horizontalOffset,
-                    ZCoordinate = point.ZCoordinate - layerThickness,
-                    PointType = CharacteristicPointType.None
-                };
-                loweredSurfaceLine.SurfaceLinePoints.Add(newPointAtDikeToe);
-            }
-
-            if (point.XCoordinate >= dikeToePolder.XCoordinate)
-            {
-                var newPointBeyondDikeToe = new SurfaceLinePoint
-                {
-                    XCoordinate = point.XCoordinate,
-                    ZCoordinate = point.ZCoordinate,
-                    PointType = point.PointType
-                };
-                loweredSurfaceLine.SurfaceLinePoints.Add(newPointBeyondDikeToe);
-            }
-        }
-
-        private static void HandlePointsUpToAndIncludingDikeTopPolder(double layerThickness, SurfaceLinePoint point,
-            SurfaceLine loweredSurfaceLine, SurfaceLinePoint dikeTopPolder, double tolerance, double horizontalOffset)
-        {
-            var newPointUpToDikeTop = new SurfaceLinePoint
-            {
-                XCoordinate = point.XCoordinate,
-                ZCoordinate = point.ZCoordinate,
-                PointType = point.PointType
-            };
-            loweredSurfaceLine.SurfaceLinePoints.Add(newPointUpToDikeTop);
-            if (Math.Abs(point.XCoordinate - dikeTopPolder.XCoordinate) < tolerance)
-            {
-                var newPointAtDikeTop = new SurfaceLinePoint
-                {
-                    XCoordinate = point.XCoordinate + horizontalOffset,
-                    ZCoordinate = point.ZCoordinate - layerThickness,
-                    PointType = CharacteristicPointType.None
-                };
-                loweredSurfaceLine.SurfaceLinePoints.Add(newPointAtDikeTop);
-            }
-        }
     }
 }
\ No newline at end of file
Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/LayerCreatorTests.cs
===================================================================
diff -u -r3184 -r3185
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/LayerCreatorTests.cs	(.../LayerCreatorTests.cs)	(revision 3184)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator.Tests/LayerCreatorTests.cs	(.../LayerCreatorTests.cs)	(revision 3185)
@@ -112,220 +112,5 @@
             Assert.IsTrue(lines[0].Contains("Handling location"));
         }
 
-        [Test]
-        public void TestDetermineLoweredSurfaceLineForGivenLayerThickness()
-        {
-            var originalSurfaceLine = CreateSimpleStraightSurfaceLine();
-            var loweredSurfaceLine = originalSurfaceLine.CreateLoweredSurfaceLineForGivenLayerThickness(1);
-            Assert.AreEqual(11,loweredSurfaceLine.SurfaceLinePoints.Count);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].ZCoordinate, Diff);
-            Assert.AreEqual(5, loweredSurfaceLine.SurfaceLinePoints[1].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[1].ZCoordinate, Diff);
-            Assert.AreEqual(10, loweredSurfaceLine.SurfaceLinePoints[2].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[2].ZCoordinate, Diff);
-            Assert.AreEqual(12, loweredSurfaceLine.SurfaceLinePoints[3].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[3].ZCoordinate, Diff);
-            Assert.AreEqual(14, loweredSurfaceLine.SurfaceLinePoints[4].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[4].ZCoordinate, Diff);
-            Assert.AreEqual(14.01, loweredSurfaceLine.SurfaceLinePoints[5].XCoordinate, Diff);
-            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[5].ZCoordinate, Diff);
-            Assert.AreEqual(15, loweredSurfaceLine.SurfaceLinePoints[6].XCoordinate, Diff);
-            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[6].ZCoordinate, Diff);
-            Assert.AreEqual(15.99, loweredSurfaceLine.SurfaceLinePoints[7].XCoordinate, Diff);
-            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[7].ZCoordinate, Diff);
-            Assert.AreEqual(16, loweredSurfaceLine.SurfaceLinePoints[8].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[8].ZCoordinate, Diff);
-            Assert.AreEqual(22, loweredSurfaceLine.SurfaceLinePoints[9].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[9].ZCoordinate, Diff);
-            Assert.AreEqual(30, loweredSurfaceLine.SurfaceLinePoints[10].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[10].ZCoordinate, Diff);
-
-        }
-
-        [Test]
-        public void TestDetermineLoweredSurfaceLineForGivenLayerThicknessWithAckwardPoints()
-        {
-            var originalSurfaceLine = CreateSimpleStraightSurfaceLineWithAckwardPoints();
-            var loweredSurfaceLine = originalSurfaceLine.CreateLoweredSurfaceLineForGivenLayerThickness(1);
-            Assert.AreEqual(11, loweredSurfaceLine.SurfaceLinePoints.Count);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[0].ZCoordinate, Diff);
-            Assert.AreEqual(5, loweredSurfaceLine.SurfaceLinePoints[1].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[1].ZCoordinate, Diff);
-            Assert.AreEqual(10, loweredSurfaceLine.SurfaceLinePoints[2].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[2].ZCoordinate, Diff);
-            Assert.AreEqual(12, loweredSurfaceLine.SurfaceLinePoints[3].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[3].ZCoordinate, Diff);
-            Assert.AreEqual(14, loweredSurfaceLine.SurfaceLinePoints[4].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[4].ZCoordinate, Diff);
-            Assert.AreEqual(14.01, loweredSurfaceLine.SurfaceLinePoints[5].XCoordinate, Diff);
-            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[5].ZCoordinate, Diff);
-            Assert.AreEqual(15.5, loweredSurfaceLine.SurfaceLinePoints[6].XCoordinate, Diff);
-            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[6].ZCoordinate, Diff);
-            Assert.AreEqual(15.99, loweredSurfaceLine.SurfaceLinePoints[7].XCoordinate, Diff);
-            Assert.AreEqual(-1, loweredSurfaceLine.SurfaceLinePoints[7].ZCoordinate, Diff);
-            Assert.AreEqual(16, loweredSurfaceLine.SurfaceLinePoints[8].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[8].ZCoordinate, Diff);
-            Assert.AreEqual(22, loweredSurfaceLine.SurfaceLinePoints[9].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[9].ZCoordinate, Diff);
-            Assert.AreEqual(30, loweredSurfaceLine.SurfaceLinePoints[10].XCoordinate, Diff);
-            Assert.AreEqual(0, loweredSurfaceLine.SurfaceLinePoints[10].ZCoordinate, Diff);
-
-        }
-        private SurfaceLine CreateSimpleStraightSurfaceLine()
-        {
-            var surfaceLine = new SurfaceLine();
-            surfaceLine.SurfaceLineId = "SimpleStraightSurfaceLine";
-            var point = new SurfaceLinePoint
-            {
-                XCoordinate = 0, ZCoordinate = 0, PointType = CharacteristicPointType.SurfaceLevelOutside
-            };
-            surfaceLine.SurfaceLinePoints.Add(point);
-            var pointA = new SurfaceLinePoint
-            {
-                XCoordinate = 5,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(pointA);
-            var point1 = new SurfaceLinePoint
-            {
-                XCoordinate = 10,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeToeAtRiver
-            };
-            surfaceLine.SurfaceLinePoints.Add(point1);
-            var point2 = new SurfaceLinePoint
-            {
-                XCoordinate = 12,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeTopAtRiver
-            };
-            surfaceLine.SurfaceLinePoints.Add(point2);
-            var point3 = new SurfaceLinePoint
-            {
-                XCoordinate = 14,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeTopAtPolder
-            };
-            surfaceLine.SurfaceLinePoints.Add(point3);
-            var point3A = new SurfaceLinePoint
-            {
-                XCoordinate = 15,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(point3A);
-            var point4 = new SurfaceLinePoint
-            {
-                XCoordinate = 16,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeToeAtPolder
-            };
-            surfaceLine.SurfaceLinePoints.Add(point4);
-            var point4A = new SurfaceLinePoint
-            {
-                XCoordinate = 22,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(point4A);
-            var point5 = new SurfaceLinePoint
-            {
-                XCoordinate = 30,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.SurfaceLevelInside
-            };
-            surfaceLine.SurfaceLinePoints.Add(point5);
-            return surfaceLine;
-        }
-
-        private SurfaceLine CreateSimpleStraightSurfaceLineWithAckwardPoints()
-        {
-            var surfaceLine = new SurfaceLine();
-            surfaceLine.SurfaceLineId = "SimpleStraightSurfaceLine";
-            var point = new SurfaceLinePoint
-            {
-                XCoordinate = 0,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.SurfaceLevelOutside
-            };
-            surfaceLine.SurfaceLinePoints.Add(point);
-            var pointA = new SurfaceLinePoint
-            {
-                XCoordinate = 5,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(pointA);
-            var point1 = new SurfaceLinePoint
-            {
-                XCoordinate = 10,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeToeAtRiver
-            };
-            surfaceLine.SurfaceLinePoints.Add(point1);
-            var point2 = new SurfaceLinePoint
-            {
-                XCoordinate = 12,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeTopAtRiver
-            };
-            surfaceLine.SurfaceLinePoints.Add(point2);
-            var point3 = new SurfaceLinePoint
-            {
-                XCoordinate = 14,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeTopAtPolder
-            };
-            surfaceLine.SurfaceLinePoints.Add(point3);
-            var point3A = new SurfaceLinePoint
-            {
-                // is less than 0.01 meter beyond the point that is to be lowered with offset of 0.01 m. So this point should NOT be found in the lowered line
-                XCoordinate = 14.001,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(point3A);
-            var point3B = new SurfaceLinePoint
-            {
-                // make this 15.5 instead of 15 to be different from ordinary SimpleStraightSurfaceLine.
-                XCoordinate = 15.5,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(point3B);
-            var point3C = new SurfaceLinePoint
-            {
-                // is less than 0.01 meter in front off the point that is to be lowered with offset of -0.01 m. So this point should NOT be found in the lowered line
-                XCoordinate = 15.999,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(point3C);
-            var point4 = new SurfaceLinePoint
-            {
-                XCoordinate = 16,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.DikeToeAtPolder
-            };
-            surfaceLine.SurfaceLinePoints.Add(point4);
-            var point4A = new SurfaceLinePoint
-            {
-                XCoordinate = 22,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.None
-            };
-            surfaceLine.SurfaceLinePoints.Add(point4A);
-            var point5 = new SurfaceLinePoint
-            {
-                XCoordinate = 30,
-                ZCoordinate = 0,
-                PointType = CharacteristicPointType.SurfaceLevelInside
-            };
-            surfaceLine.SurfaceLinePoints.Add(point5);
-            return surfaceLine;
-        }
     }
 }
\ No newline at end of file
Index: DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/SurfacelineProcessor.cs
===================================================================
diff -u
--- DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/SurfacelineProcessor.cs	(revision 0)
+++ DamTools/LayerOnSlopeTool/trunk/src/Deltares.LayerOnSlopeTool.LayerCreator/SurfacelineProcessor.cs	(revision 3185)
@@ -0,0 +1,134 @@
+// Copyright (C) Stichting Deltares 2019. All rights reserved.
+//
+// This file is part of the Dam Engine.
+//
+// The Dam Engine is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using System;
+using Deltares.LayerOnSlopeTool.Data;
+
+namespace Deltares.LayerOnSlopeTool.LayerCreator
+{
+    /// <summary></summary>
+    public class SurfacelineProcessor
+    {
+        private const double tolerance = 1e-4;
+        private const double horizontalOffset = 0.01;
+        private readonly SurfaceLine surfaceLine;
+        private SurfaceLinePoint dikeTopPolder;
+        private SurfaceLinePoint dikeToePolder;
+
+        /// <summary>Initializes a new instance of the <see cref="SurfacelineProcessor"/> class.</summary>
+        /// <param name="orgSurfaceLine">The org surface line.</param>
+        public SurfacelineProcessor(SurfaceLine orgSurfaceLine)
+        {
+            surfaceLine = orgSurfaceLine;
+            dikeTopPolder = surfaceLine.GetSurfaceLinePointByType(CharacteristicPointType.DikeTopAtPolder);
+            dikeToePolder = surfaceLine.GetSurfaceLinePointByType(CharacteristicPointType.DikeToeAtPolder);
+
+        }
+
+        /// <summary>Creates the lowered surface line.</summary>
+        /// <param name="layerThickness">The layer thickness.</param>
+        /// <returns></returns>
+        public SurfaceLine CreateLoweredSurfaceLine(double layerThickness)
+        {
+            var loweredSurfaceLine = new SurfaceLine();
+            foreach (var point in surfaceLine.SurfaceLinePoints)
+            {
+                if (point.XCoordinate <= dikeTopPolder.XCoordinate)
+                {
+                    HandlePointsUpToAndIncludingDikeTopPolder(layerThickness, point, loweredSurfaceLine);
+                }
+                else
+                {
+                    if (point.XCoordinate > dikeTopPolder.XCoordinate + horizontalOffset && 
+                        point.XCoordinate < dikeToePolder.XCoordinate - horizontalOffset)
+                    {
+                        HandlePointsBetweenDiketopPolderAndDikeToePolder(layerThickness, point, loweredSurfaceLine);
+                    }
+                    else
+                    {
+                        HandlePointsAtDikeToePolderAndBeyond(layerThickness, point, loweredSurfaceLine);
+                    }
+                }
+            }
+            return loweredSurfaceLine;
+        }
+
+        private static void HandlePointsBetweenDiketopPolderAndDikeToePolder(double layerThickness, 
+            SurfaceLinePoint point, SurfaceLine loweredSurfaceLine)
+        {
+            var newPointLowered = new SurfaceLinePoint
+            {
+                XCoordinate = point.XCoordinate,
+                ZCoordinate = point.ZCoordinate - layerThickness,
+                PointType = point.PointType
+            };
+            loweredSurfaceLine.SurfaceLinePoints.Add(newPointLowered);
+        }
+
+        private void HandlePointsAtDikeToePolderAndBeyond(double layerThickness, 
+            SurfaceLinePoint point, SurfaceLine loweredSurfaceLine)
+        {
+            if (Math.Abs(point.XCoordinate - dikeToePolder.XCoordinate) < tolerance)
+            {
+                var newPointAtDikeToe = new SurfaceLinePoint
+                {
+                    XCoordinate = point.XCoordinate - horizontalOffset,
+                    ZCoordinate = point.ZCoordinate - layerThickness,
+                    PointType = CharacteristicPointType.None
+                };
+                loweredSurfaceLine.SurfaceLinePoints.Add(newPointAtDikeToe);
+            }
+
+            if (point.XCoordinate >= dikeToePolder.XCoordinate)
+            {
+                var newPointBeyondDikeToe = new SurfaceLinePoint
+                {
+                    XCoordinate = point.XCoordinate,
+                    ZCoordinate = point.ZCoordinate,
+                    PointType = point.PointType
+                };
+                loweredSurfaceLine.SurfaceLinePoints.Add(newPointBeyondDikeToe);
+            }
+        }
+
+        private void HandlePointsUpToAndIncludingDikeTopPolder(double layerThickness, SurfaceLinePoint point,
+            SurfaceLine loweredSurfaceLine)
+        {
+            var newPointUpToDikeTop = new SurfaceLinePoint
+            {
+                XCoordinate = point.XCoordinate,
+                ZCoordinate = point.ZCoordinate,
+                PointType = point.PointType
+            };
+            loweredSurfaceLine.SurfaceLinePoints.Add(newPointUpToDikeTop);
+            if (Math.Abs(point.XCoordinate - dikeTopPolder.XCoordinate) < tolerance)
+            {
+                var newPointAtDikeTop = new SurfaceLinePoint
+                {
+                    XCoordinate = point.XCoordinate + horizontalOffset,
+                    ZCoordinate = point.ZCoordinate - layerThickness,
+                    PointType = CharacteristicPointType.None
+                };
+                loweredSurfaceLine.SurfaceLinePoints.Add(newPointAtDikeTop);
+            }
+        }
+    }
+}
\ No newline at end of file