Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Calculation/Math2D.cs
===================================================================
diff -u
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Calculation/Math2D.cs	(revision 0)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Calculation/Math2D.cs	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -0,0 +1,128 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using Ringtoets.Piping.Data.Properties;
+
+namespace Ringtoets.Piping.Data.Calculation
+{
+    /// <summary>
+    /// This class contains general mathematical routines for 2D lines.
+    /// </summary>
+    public static class Math2D
+    {
+        /// <summary>
+        /// Constant which is used to precision errors in <see cref="double"/> comparisons.
+        /// </summary>
+        private const double epsilonForComparisons = 1e-8;
+
+        /// <summary>
+        /// Determines the intersection point of a line which passes through the <paramref name="line1Point1"/> and 
+        /// the <paramref name="line1Point2"/>; and a line which passes through the <paramref name="line2Point1"/>
+        /// and the <paramref name="line2Point2"/>.
+        /// </summary>
+        /// <param name="line1Point1">A <see cref="Point2D"/> which the first line passes through.</param>
+        /// <param name="line1Point2">Another <see cref="Point2D"/> which the first line passes through.</param>
+        /// <param name="line2Point1">A <see cref="Point2D"/> which the second line passes through.</param>
+        /// <param name="line2Point2">Another <see cref="Point2D"/> which the second line passes through.</param>
+        /// <returns>An <see cref="Point2D"/> with coordinates at the point where the lines intersect. Or <c>null</c> when no
+        /// intersection point exists (lines are parallel).</returns>
+        /// <remarks>
+        /// <para>Taken from: https://www.topcoder.com/community/data-science/data-science-tutorials/geometry-concepts-line-intersection-and-its-applications/ </para>
+        /// <para>Based on https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection </para>
+        /// </remarks>
+        /// <exception cref="ArgumentException">Thrown when <paramref name="line1Point1"/> equals <paramref name="line1Point2"/> or 
+        /// <paramref name="line2Point1"/> equals <paramref name="line2Point2"/>, which makes it impossible to determine
+        /// a line through the points.</exception>
+        public static Point2D LineIntersectionWithLine(Point2D line1Point1, Point2D line1Point2, Point2D line2Point1, Point2D line2Point2)
+        {
+            if (line1Point1.Equals(line1Point2) || line2Point1.Equals(line2Point2))
+            {
+                throw new ArgumentException(Resources.Math2D_LineIntersectionWithLine_Line_points_are_equal);
+            }
+
+            var aLine = line1Point2.Y - line1Point1.Y;
+            var bLine = line1Point1.X - line1Point2.X;
+            var cLine = aLine*line1Point1.X + bLine*line1Point1.Y;
+
+            var aOtherLine = line2Point2.Y - line2Point1.Y;
+            var bOtherLine = line2Point1.X - line2Point2.X;
+            var cOtherLine = aOtherLine*line2Point1.X + bOtherLine*line2Point1.Y;
+
+            var determinant = aLine*bOtherLine - aOtherLine*bLine;
+            if (Math.Abs(determinant) < epsilonForComparisons)
+            {
+                return null;
+            }
+
+            return new Point2D
+            {
+                X = (bOtherLine*cLine - bLine*cOtherLine)/determinant,
+                Y = (aLine*cOtherLine - aOtherLine*cLine)/determinant
+            };
+        }
+
+        /// <summary>
+        /// Determines the intersection points of a <see cref="IEnumerable{T}"/> of <see cref="Segment2D"/> with a vertical line
+        /// which is plotted at x=<paramref name="verticalLineX"/>.
+        /// </summary>
+        /// <param name="segments">A collection of segments that possibly intersect with the
+        /// vertical line at x=<paramref name="verticalLineX"/>.</param>
+        /// <param name="verticalLineX">The x coordinate of the vertical line.</param>
+        /// <returns>A <see cref="IEnumerable{T}"/> of <see cref="Point2D"/> with all intersection points of the 
+        /// <paramref name="segments"/> with the vertical line at x=<paramref name="verticalLineX"/>.</returns>
+        /// <remark>Segments which have length=0 or which are vertical, will not return an intersection point.</remark>
+        public static IEnumerable<Point2D> SegmentsIntersectionWithVerticalLine(IEnumerable<Segment2D> segments, double verticalLineX)
+        {
+            var intersectionPointY = new Collection<Point2D>();
+
+            foreach (Segment2D segment in segments.Where(s => s.ContainsX(verticalLineX)))
+            {
+                Point2D intersectionPoint = LineIntersectionWithVerticalLine(segment.FirstPoint, segment.SecondPoint, verticalLineX);
+
+                if (intersectionPoint != null)
+                {
+                    intersectionPointY.Add(intersectionPoint);
+                }
+            }
+
+            return intersectionPointY;
+        }
+
+        /// <summary>
+        /// Determines the intersection point of a line through the points <paramref name="point1"/> and
+        /// <paramref name="point2"/> with a vertical line at x=<paramref name="x"/>. If 
+        /// <paramref name="point1"/> equals <paramref name="point2"/>, then no intersection point 
+        /// will be returned.
+        /// </summary>
+        /// <param name="point1">A <see cref="Point2D"/> which the line passes through.</param>
+        /// <param name="point2">Another <see cref="Point2D"/> which the line passes through.</param>
+        /// <param name="x">The x coordinate of the vertical line.</param>
+        /// <returns>The intersection point between the line through <paramref name="point1"/> and
+        /// <paramref name="point2"/> and the vertical line at x=<paramref name="x"/>; or null if
+        /// the line through <paramref name="point1"/> and <paramref name="point2"/> is vertical or
+        /// the points are equal.</returns>
+        private static Point2D LineIntersectionWithVerticalLine(Point2D point1, Point2D point2, double x)
+        {
+            var verticalLineFirstPoint = new Point2D
+            {
+                X = x,
+                Y = 0
+            };
+            var verticalLineSecondPoint = new Point2D
+            {
+                X = x,
+                Y = 1
+            };
+
+            try
+            {
+                return LineIntersectionWithLine(point1, point2, verticalLineFirstPoint, verticalLineSecondPoint);
+            }
+            catch (ArgumentException)
+            {
+                return null;
+            }
+        }
+    }
+}
\ No newline at end of file
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Exceptions/RingtoetsPipingSurfaceLineException.cs
===================================================================
diff -u
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Exceptions/RingtoetsPipingSurfaceLineException.cs	(revision 0)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Exceptions/RingtoetsPipingSurfaceLineException.cs	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -0,0 +1,33 @@
+using System;
+
+namespace Ringtoets.Piping.Data.Exceptions
+{
+    /// <summary>
+    /// The exception that is thrown when operations on <see cref="RingtoetsPipingSurfaceLine"/> encounter 
+    /// an error.
+    /// </summary>
+    public class RingtoetsPipingSurfaceLineException : Exception
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RingtoetsPipingSurfaceLineException"/> class.
+        /// </summary>
+        public RingtoetsPipingSurfaceLineException(){}
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RingtoetsPipingSurfaceLineException"/> class
+        /// with a specified error message.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        public RingtoetsPipingSurfaceLineException(string message) : base(message){}
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RingtoetsPipingSurfaceLineException"/> class
+        /// with a specified error message and a reference to the inner exception that is
+        /// the cause of this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="inner">The exception that is the cause of the current exception, 
+        /// or a null reference if no inner exception is specified.</param>
+        public RingtoetsPipingSurfaceLineException(string message, Exception inner) : base(message, inner) { }
+    }
+}
\ No newline at end of file
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Point2D.cs
===================================================================
diff -u -r2da86d14cee084c7d6bfa52136d387cdcdb0a025 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Point2D.cs	(.../Point2D.cs)	(revision 2da86d14cee084c7d6bfa52136d387cdcdb0a025)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Point2D.cs	(.../Point2D.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -87,7 +87,7 @@
         /// </summary>
         /// <param name="other">A <see cref="Point2D"/> to compare with.</param>
         /// <returns>True if the coordinates of the <see cref="Point3D"/> matches the coordinate of <paramref name="other"/>. False otherwise.</returns>
-        protected bool Equals(Point2D other)
+        private bool Equals(Point2D other)
         {
             return X.Equals(other.X) && Y.Equals(other.Y);
         }
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Properties/Resources.Designer.cs
===================================================================
diff -u -r394db7c1bd905eb7444b9b2c47bcb5111bb63af6 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision 394db7c1bd905eb7444b9b2c47bcb5111bb63af6)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -1,7 +1,7 @@
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
-//     Runtime Version:4.0.30319.18444
+//     Runtime Version:4.0.30319.34209
 //
 //     Changes to this file may cause incorrect behavior and will be lost if
 //     the code is regenerated.
@@ -106,6 +106,25 @@
         }
         
         /// <summary>
+        ///   Looks up a localized string similar to Punten voor een lijn moeten uit elkaar liggen om een lijn te kunnen vormen..
+        /// </summary>
+        internal static string Math2D_LineIntersectionWithLine_Line_points_are_equal {
+            get {
+                return ResourceManager.GetString("Math2D_LineIntersectionWithLine_Line_points_are_equal", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to Kan geen hoogte bepalen op het punt L={0}, omdate de dwarsdoorsnede verticaal loopt op dat punt..
+        /// </summary>
+        internal static string RingtoetsPipingSurfaceLine_Cannot_determine_reliable_z_when_surface_line_is_vertical_in_l {
+            get {
+                return ResourceManager.GetString("RingtoetsPipingSurfaceLine_Cannot_determine_reliable_z_when_surface_line_is_verti" +
+                        "cal_in_l", resourceCulture);
+            }
+        }
+        
+        /// <summary>
         ///   Looks up a localized string similar to Voor het maken van een segment zijn twee punten nodig..
         /// </summary>
         internal static string Segment2D_Constructor_Segment_must_be_created_with_two_points {
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Properties/Resources.resx
===================================================================
diff -u -r394db7c1bd905eb7444b9b2c47bcb5111bb63af6 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Properties/Resources.resx	(.../Resources.resx)	(revision 394db7c1bd905eb7444b9b2c47bcb5111bb63af6)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Properties/Resources.resx	(.../Resources.resx)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -138,4 +138,10 @@
   <data name="LognormalDistribution_Mean_must_be_greater_equal_to_zero" xml:space="preserve">
     <value>Gemiddelde moet groter zijn dan 0.</value>
   </data>
+  <data name="Math2D_LineIntersectionWithLine_Line_points_are_equal" xml:space="preserve">
+    <value>Punten voor een lijn moeten uit elkaar liggen om een lijn te kunnen vormen.</value>
+  </data>
+  <data name="RingtoetsPipingSurfaceLine_Cannot_determine_reliable_z_when_surface_line_is_vertical_in_l" xml:space="preserve">
+    <value>Kan geen hoogte bepalen op het punt L={0}, omdate de dwarsdoorsnede verticaal loopt op dat punt.</value>
+  </data>
 </root>
\ No newline at end of file
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Ringtoets.Piping.Data.csproj
===================================================================
diff -u -r394db7c1bd905eb7444b9b2c47bcb5111bb63af6 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Ringtoets.Piping.Data.csproj	(.../Ringtoets.Piping.Data.csproj)	(revision 394db7c1bd905eb7444b9b2c47bcb5111bb63af6)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Ringtoets.Piping.Data.csproj	(.../Ringtoets.Piping.Data.csproj)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -38,6 +38,9 @@
     </DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
+    <Reference Include="Deltares.WTIPiping">
+      <HintPath>..\..\..\..\lib\Plugins\Wti\Deltares.WTIPiping.dll</HintPath>
+    </Reference>
     <Reference Include="MathNet.Numerics, Version=3.8.0.0, Culture=neutral, processorArchitecture=MSIL">
       <HintPath>..\..\..\..\packages\MathNet.Numerics.3.8.0\lib\net40\MathNet.Numerics.dll</HintPath>
       <Private>True</Private>
@@ -50,6 +53,8 @@
     <Compile Include="..\..\..\..\Core\Common\src\Core.Common.Version\GlobalAssembly.cs">
       <Link>Properties\GlobalAssembly.cs</Link>
     </Compile>
+    <Compile Include="Calculation\Math2D.cs" />
+    <Compile Include="Exceptions\RingtoetsPipingSurfaceLineException.cs" />
     <Compile Include="PipingData.cs" />
     <Compile Include="PipingFailureMechanism.cs" />
     <Compile Include="PipingOutput.cs" />
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/RingtoetsPipingSurfaceLine.cs
===================================================================
diff -u -r5462a7ee52b9491f269d489a094d359f4f02f270 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/RingtoetsPipingSurfaceLine.cs	(.../RingtoetsPipingSurfaceLine.cs)	(revision 5462a7ee52b9491f269d489a094d359f4f02f270)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/RingtoetsPipingSurfaceLine.cs	(.../RingtoetsPipingSurfaceLine.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -1,8 +1,12 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 
 using MathNet.Numerics.LinearAlgebra.Double;
+using Ringtoets.Piping.Data.Calculation;
+using Ringtoets.Piping.Data.Exceptions;
+using Ringtoets.Piping.Data.Properties;
 
 namespace Ringtoets.Piping.Data
 {
@@ -64,6 +68,34 @@
         }
 
         /// <summary>
+        /// Gets the height of the projected <see cref="RingtoetsPipingSurfaceLine"/> at a L=<paramref name="l"/>.
+        /// </summary>
+        /// <param name="l">The L coordinate from where to take the height of the <see cref="RingtoetsPipingSurfaceLine"/>.</param>
+        /// <returns>The height of the <see cref="RingtoetsPipingSurfaceLine"/> at L=<paramref name="l"/>.</returns>
+        /// <exception cref="RingtoetsPipingSurfaceLineException">Thrown when the <see cref="RingtoetsPipingSurfaceLine"/>
+        /// intersection point at <paramref name="l"/> have a significant difference in their y coordinate.</exception>
+        public double GetZAtL(double l)
+        {
+            var projectGeometryToLz = ProjectGeometryToLZ().ToArray();
+            var segments = new Collection<Segment2D>();
+            for (int i = 1; i < projectGeometryToLz.Length; i++)
+            {
+                segments.Add(new Segment2D(projectGeometryToLz[i-1], projectGeometryToLz[i]));   
+            }
+
+            var intersectionPoints = Math2D.SegmentsIntersectionWithVerticalLine(segments, l).OrderBy(p => p.Y).ToArray();
+            var equalIntersections = Math.Abs(intersectionPoints.First().Y - intersectionPoints.Last().Y) < 1e-8;
+
+            if (equalIntersections)
+            {
+                return intersectionPoints.First().Y;
+            }
+
+            var message = string.Format(Resources.RingtoetsPipingSurfaceLine_Cannot_determine_reliable_z_when_surface_line_is_vertical_in_l, l);
+            throw new RingtoetsPipingSurfaceLineException(message);
+        }
+
+        /// <summary>
         /// Projects the points in <see cref="Points"/> to localized coordinate (LZ-plane) system.
         /// Z-values are retained, and the first point is put a L=0.
         /// </summary>
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/Segment2D.cs
===================================================================
diff -u -r72802865521b0ddd696ff95ab01573feb4bd0cb0 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/Segment2D.cs	(.../Segment2D.cs)	(revision 72802865521b0ddd696ff95ab01573feb4bd0cb0)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/Segment2D.cs	(.../Segment2D.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -59,7 +59,7 @@
         /// <returns><c>true</c> if the <see cref="Segment2D"/> is vertical. <c>false</c> otherwise.</returns>
         public bool IsVertical()
         {
-            return Math.Abs(FirstPoint.X - SecondPoint.X) < 1e-8 && !FirstPoint.Y.Equals(SecondPoint.Y);
+            return Math.Abs(FirstPoint.X - SecondPoint.X) < 1e-8 && Math.Abs(FirstPoint.Y - SecondPoint.Y) >= 1e-8;
         }
 
         /// <summary>
Index: Ringtoets/Piping/src/Ringtoets.Piping.IO/Builders/SoilLayer2D.cs
===================================================================
diff -u -r72802865521b0ddd696ff95ab01573feb4bd0cb0 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.IO/Builders/SoilLayer2D.cs	(.../SoilLayer2D.cs)	(revision 72802865521b0ddd696ff95ab01573feb4bd0cb0)
+++ Ringtoets/Piping/src/Ringtoets.Piping.IO/Builders/SoilLayer2D.cs	(.../SoilLayer2D.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -4,7 +4,7 @@
 using System.Linq;
 using System.Linq.Expressions;
 using Ringtoets.Piping.Data;
-using Ringtoets.Piping.IO.Calculation;
+using Ringtoets.Piping.Data.Calculation;
 using Ringtoets.Piping.IO.Properties;
 
 namespace Ringtoets.Piping.IO.Builders
Fisheye: Tag 712a020ea0330ece24849c2710641c1ce399ed61 refers to a dead (removed) revision in file `Ringtoets/Piping/src/Ringtoets.Piping.IO/Calculation/Math2D.cs'.
Fisheye: No comparison available.  Pass `N' to diff?
Index: Ringtoets/Piping/src/Ringtoets.Piping.IO/Properties/Resources.Designer.cs
===================================================================
diff -u -r1efcd2277f5a38d44a78e4a9286eec35134fe8dd -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.IO/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision 1efcd2277f5a38d44a78e4a9286eec35134fe8dd)
+++ Ringtoets/Piping/src/Ringtoets.Piping.IO/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -178,15 +178,6 @@
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Punten voor een lijn moeten uit elkaar liggen om een lijn te kunnen vormen..
-        /// </summary>
-        public static string Math2D_LineIntersectionWithLine_Line_points_are_equal {
-            get {
-                return ResourceManager.GetString("Math2D_LineIntersectionWithLine_Line_points_are_equal", resourceCulture);
-            }
-        }
-        
-        /// <summary>
         ///   Looks up a localized string similar to Kon profiel &apos;{0}&apos; niet opbouwen vanuit de gegevens uit de database..
         /// </summary>
         public static string PipingSoilProfileReader_Could_not_build_profile_0_from_layer_definitions {
Index: Ringtoets/Piping/src/Ringtoets.Piping.IO/Properties/Resources.resx
===================================================================
diff -u -r1efcd2277f5a38d44a78e4a9286eec35134fe8dd -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.IO/Properties/Resources.resx	(.../Resources.resx)	(revision 1efcd2277f5a38d44a78e4a9286eec35134fe8dd)
+++ Ringtoets/Piping/src/Ringtoets.Piping.IO/Properties/Resources.resx	(.../Resources.resx)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -189,9 +189,6 @@
   <data name="PipingSoilProfileReader_Critical_Unexpected_value_on_column" xml:space="preserve">
     <value>Kritieke fout opgetreden bij het uitlezen van waarden uit kolommen in de database.</value>
   </data>
-  <data name="Math2D_LineIntersectionWithLine_Line_points_are_equal" xml:space="preserve">
-    <value>Punten voor een lijn moeten uit elkaar liggen om een lijn te kunnen vormen.</value>
-  </data>
   <data name="SoilLayer2DReader_Geometry_contains_no_valid_xml" xml:space="preserve">
     <value>Het XML document dat de geometrie beschrijft voor de laag is niet geldig.</value>
   </data>
Index: Ringtoets/Piping/src/Ringtoets.Piping.IO/Ringtoets.Piping.IO.csproj
===================================================================
diff -u -r069921ae1e06e13d8e5e19dd9caa5e8f7b9e1f35 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/src/Ringtoets.Piping.IO/Ringtoets.Piping.IO.csproj	(.../Ringtoets.Piping.IO.csproj)	(revision 069921ae1e06e13d8e5e19dd9caa5e8f7b9e1f35)
+++ Ringtoets/Piping/src/Ringtoets.Piping.IO/Ringtoets.Piping.IO.csproj	(.../Ringtoets.Piping.IO.csproj)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -47,7 +47,6 @@
     <Compile Include="Builders\SoilLayer2DConversionException.cs" />
     <Compile Include="Builders\SoilProfileBuilder1D.cs" />
     <Compile Include="Builders\SoilProfileBuilder2D.cs" />
-    <Compile Include="Calculation\Math2D.cs" />
     <Compile Include="Exceptions\CriticalFileReadException.cs" />
     <Compile Include="Exceptions\LineParseException.cs" />
     <Compile Include="Exceptions\PipingSoilProfileReadException.cs" />
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Calculation/Math2DTest.cs
===================================================================
diff -u
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Calculation/Math2DTest.cs	(revision 0)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Calculation/Math2DTest.cs	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -0,0 +1,208 @@
+using System;
+using System.Collections;
+using System.Linq;
+using NUnit.Framework;
+using Ringtoets.Piping.Data.Calculation;
+
+namespace Ringtoets.Piping.Data.Test.Calculation
+{
+    [TestFixture]
+    public class Math2DTest
+    {
+        #region testcases
+
+        /// <summary>
+        /// Test cases for intersecting segments. The <see cref="Array"/> contains pairs of <see cref="double"/>,
+        /// which represent the coordinate of a point. Each pair of coordinates form a segment. 
+        /// The last 2 double values are the expected intersection points.
+        /// </summary>
+        private static IEnumerable IntersectingSegments()
+        {
+            // \/
+            // /\
+            var testCaseDatadata1 = new TestCaseData(new[]
+            {
+                new Point2D(0.0,0.0),
+                new Point2D(1.0,1.0),
+                new Point2D(1.0,0.0),
+                new Point2D(0.0,1.0),
+                new Point2D(0.5,0.5)
+            }, "IntersectingSegments 1");
+            yield return testCaseDatadata1; 
+
+            // __
+            //  /
+            // /
+            var testCaseDatadata2 = new TestCaseData(new[]
+            {
+                new Point2D(0.0,0.0),
+                new Point2D(1.0,1.0),
+                new Point2D(0.0,1.0),
+                new Point2D(1.0,1.0),
+                new Point2D(1.0,1.0)
+            }, "IntersectingSegments 2");
+            yield return testCaseDatadata2;
+
+            // 
+            //  /
+            // /__
+            var testCaseDatadata3 = new TestCaseData(new[]
+            {
+                new Point2D(0.0,0.0),
+                new Point2D(1.0,0.0),
+                new Point2D(0.0,0.0),
+                new Point2D(1.0,1.0),
+                new Point2D(0.0,0.0)
+            }, "IntersectingSegments 3");
+            yield return testCaseDatadata3;
+        }
+
+        /// <summary>
+        /// Test cases for parallel segments. The <see cref="Array"/> contains pairs of <see cref="double"/>,
+        /// which represent the coordinate of a point. Each pair of coordinates form a segment.
+        /// </summary>
+        private static IEnumerable ParallelSegments()
+        {
+
+            // __
+            // __
+            var testCaseDatadata1 = new TestCaseData(new[]
+            {
+                new Point2D(0.0, 0.0),
+                new Point2D(1.0, 0.0),
+                new Point2D(0.0, 1.0),
+                new Point2D(1.0, 1.0)
+            }, "ParallelSegments");
+            yield return testCaseDatadata1; 
+
+            
+           // ____ (connected in single point)
+            var testCaseDatadata2 = new TestCaseData(new[]
+            {
+                new Point2D(0.0, 0.0),
+                new Point2D(1.0, 0.0),
+                new Point2D(1.0, 0.0),
+                new Point2D(2.0, 0.0)
+            }, "ParallelSegments, connected in single point");
+            yield return testCaseDatadata2;
+
+
+            // __ (overlap)
+            var testCaseDatadata3 = new TestCaseData(new[]
+            {
+                new Point2D(0.0, 0.0),
+                new Point2D(1.0, 0.0),
+                new Point2D(0.5, 0.0),
+                new Point2D(1.5, 0.0)
+            }, "ParallelSegments, overlap");
+            yield return testCaseDatadata3;
+        }
+
+        /// <summary>
+        /// Test cases for non intersecting segments. The <see cref="Array"/> contains pairs of <see cref="double"/>,
+        /// which represent the coordinate of a point. Each pair of coordinates form a segment.
+        /// </summary>
+        private static readonly Point2D[][] NonIntersectingSegments =
+        {
+            //  |
+            // ___
+            new[]
+            {
+                new Point2D(0.0,0.0),
+                new Point2D(1.0,0.0),
+                new Point2D(0.5,1.0),
+                new Point2D(0.5,0.5),
+                new Point2D(0.5,0.0)
+            }
+        };
+
+        #endregion
+
+        [Test]
+        [TestCaseSource("IntersectingSegments")]
+        public void LineIntersectionWithLine_DifferentLineSegmentsWithIntersections_ReturnsPoint(Point2D[] points, string testname = "")
+        {
+            // Call
+            var result = Math2D.LineIntersectionWithLine(points[0], points[1], points[2], points[3]);
+
+            // Assert
+            Assert.AreEqual(points[4], result);
+        }
+
+        [Test]
+        [TestCaseSource("ParallelSegments")]
+        // String testname was added because the Teamcity report only counts the unique signatures that were tested
+        public void LineIntersectionWithLine_DifferentParallelLineSegments_ReturnsNoPoint(Point2D[] points, string testname="")
+        {
+            // Call
+            var result = Math2D.LineIntersectionWithLine(points[0], points[1], points[2], points[3]);
+
+            // Assert
+            Assert.IsNull(result);
+        }
+
+        [Test]
+        [TestCaseSource("NonIntersectingSegments")]
+        public void LineIntersectionWithLine_DifferentLineSegmentsWithNoIntersection_ReturnsPoint(Point2D[] points)
+        {
+            // Call
+            var result = Math2D.LineIntersectionWithLine(points[0], points[1], points[2], points[3]);
+
+            // Assert
+            Assert.AreEqual(points[4], result);
+        }
+
+        [Test]
+        public void LineIntersectionWithLine_WithEqualPoints_ThrowsArgumentException()
+        {
+            // Call
+            TestDelegate testA = () => Math2D.LineIntersectionWithLine(new Point2D(0,0), new Point2D(0,0), new Point2D(1,0), new Point2D(0,1));
+            TestDelegate testB = () => Math2D.LineIntersectionWithLine(new Point2D(0, 1), new Point2D(0, 0), new Point2D(1, 1), new Point2D(1, 1));
+
+            // Assert
+            var exceptionA = Assert.Throws<ArgumentException>(testA);
+            var exceptionB = Assert.Throws<ArgumentException>(testB);
+            Assert.AreEqual(Properties.Resources.Math2D_LineIntersectionWithLine_Line_points_are_equal, exceptionA.Message);
+            Assert.AreEqual(Properties.Resources.Math2D_LineIntersectionWithLine_Line_points_are_equal,exceptionB.Message);
+        }
+
+        [Test]
+        public void LineIntersectionWithLine_InterSectionsHigherUpX_ReturnsIntersectionWithTolerance()
+        {
+            // Setup
+            var y1 = 5.925;
+            var y2 = 5.890;
+            var start = 133;
+
+            // Call
+            var result = Math2D.LineIntersectionWithLine(new Point2D(start, y1), new Point2D(start + 1, y2), new Point2D(start + 0.5, 0), new Point2D(start + 0.5, 1));
+
+            // Assert
+            Assert.AreEqual((y1+y2)/2, result.Y, 1e-8);
+        }
+
+        [Test]
+        [TestCase(2.5, new [] {3.3})]
+        [TestCase(1.1, new double[0])]
+        [TestCase(5.5, new double[0])]
+        [TestCase(-1.5, new []{1.5, 3.75})]
+        public void SegmentsIntersectionWithVerticalLine_SegmentsCollectionNotIntersecting_ReturnsEmptyCollection(double x, double[] intersectionHeights)
+        {
+            // Setup
+            var segments = new[]
+            {
+                new Segment2D(new Point2D(2.2,3.3), new Point2D(3.3,3.3)),
+                new Segment2D(new Point2D(1.1,5.0), new Point2D(1.1,2.0)), // vertical
+                new Segment2D(new Point2D(5.5,2.0), new Point2D(5.5,2.0)), // no length
+                new Segment2D(new Point2D(-2.0,1.0), new Point2D(-1.0,2.0)),
+                new Segment2D(new Point2D(-1.0,2.0), new Point2D(-2.0,5.5))
+            };
+
+            // Call
+            var result = Math2D.SegmentsIntersectionWithVerticalLine(segments, x);
+
+            // Assert
+            Assert.AreEqual(intersectionHeights.Select(y => new Point2D(x, y)), result);
+        }
+    }
+}
\ No newline at end of file
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Exceptions/RingtoetsPipingSurfaceLineExceptionTest.cs
===================================================================
diff -u
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Exceptions/RingtoetsPipingSurfaceLineExceptionTest.cs	(revision 0)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Exceptions/RingtoetsPipingSurfaceLineExceptionTest.cs	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -0,0 +1,70 @@
+using System;
+using NUnit.Framework;
+using Ringtoets.Piping.Data.Exceptions;
+
+namespace Ringtoets.Piping.Data.Test.Exceptions
+{
+    [TestFixture]
+    public class RingtoetsPipingSurfaceLineExceptionExceptionTest
+    {
+        [Test]
+        [SetCulture("en-US")]
+        public void DefaultConstructor_ExpectedValues()
+        {
+            // Call
+            var exception = new RingtoetsPipingSurfaceLineException();
+
+            // Assert
+            Assert.IsInstanceOf<Exception>(exception);
+            var expectedMessage = string.Format("Exception of type '{0}' was thrown.", exception.GetType());
+            Assert.AreEqual(expectedMessage, exception.Message);
+            CollectionAssert.IsEmpty(exception.Data);
+            Assert.IsNull(exception.HelpLink);
+            Assert.IsNull(exception.InnerException);
+            Assert.IsNull(exception.Source);
+            Assert.IsNull(exception.StackTrace);
+            Assert.IsNull(exception.TargetSite);
+        }
+
+        [Test]
+        public void MessageConstructor_ExpectedValues()
+        {
+            // Setup
+            const string messageText = "<insert exception message>";
+
+            // Call
+            var exception = new RingtoetsPipingSurfaceLineException(messageText);
+
+            // Assert
+            Assert.IsInstanceOf<Exception>(exception);
+            Assert.AreEqual(messageText, exception.Message);
+            CollectionAssert.IsEmpty(exception.Data);
+            Assert.IsNull(exception.HelpLink);
+            Assert.IsNull(exception.InnerException);
+            Assert.IsNull(exception.Source);
+            Assert.IsNull(exception.StackTrace);
+            Assert.IsNull(exception.TargetSite);
+        }
+
+        [Test]
+        public void MessageAndInnerExceptionConstructor_ExpectedValues()
+        {
+            // Setup
+            var innerException = new Exception();
+            const string messageText = "<insert exception message>";
+
+            // Call
+            var exception = new RingtoetsPipingSurfaceLineException(messageText, innerException);
+
+            // Assert
+            Assert.IsInstanceOf<Exception>(exception);
+            Assert.AreEqual(messageText, exception.Message);
+            CollectionAssert.IsEmpty(exception.Data);
+            Assert.IsNull(exception.HelpLink);
+            Assert.AreEqual(innerException, exception.InnerException);
+            Assert.IsNull(exception.Source);
+            Assert.IsNull(exception.StackTrace);
+            Assert.IsNull(exception.TargetSite);
+        }
+    }
+} 
\ No newline at end of file
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Ringtoets.Piping.Data.Test.csproj
===================================================================
diff -u -r394db7c1bd905eb7444b9b2c47bcb5111bb63af6 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Ringtoets.Piping.Data.Test.csproj	(.../Ringtoets.Piping.Data.Test.csproj)	(revision 394db7c1bd905eb7444b9b2c47bcb5111bb63af6)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Ringtoets.Piping.Data.Test.csproj	(.../Ringtoets.Piping.Data.Test.csproj)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -48,6 +48,8 @@
     <Reference Include="System.Numerics" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Calculation\Math2DTest.cs" />
+    <Compile Include="Exceptions\RingtoetsPipingSurfaceLineExceptionTest.cs" />
     <Compile Include="PipingDataTest.cs" />
     <Compile Include="PipingFailureMechanismTest.cs" />
     <Compile Include="PipingOutputTest.cs" />
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/RingtoetsPipingSurfaceLineTest.cs
===================================================================
diff -u -r5462a7ee52b9491f269d489a094d359f4f02f270 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/RingtoetsPipingSurfaceLineTest.cs	(.../RingtoetsPipingSurfaceLineTest.cs)	(revision 5462a7ee52b9491f269d489a094d359f4f02f270)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/RingtoetsPipingSurfaceLineTest.cs	(.../RingtoetsPipingSurfaceLineTest.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -3,6 +3,7 @@
 using System.Linq;
 
 using NUnit.Framework;
+using Ringtoets.Piping.Data.Exceptions;
 
 namespace Ringtoets.Piping.Data.Test
 {
@@ -157,6 +158,53 @@
         }
 
         [Test]
+        public void GetZAtL_SurfaceLineContainsPointAtL_ReturnsZOfPoint()
+        {
+            // Setup
+            var testZ = new Random(22).NextDouble();
+
+            var surfaceLine = new RingtoetsPipingSurfaceLine();
+            var l = 2.0;
+            surfaceLine.SetGeometry(new[]
+            {
+                new Point3D { X = 0.0, Y = 0.0, Z = 2.2 }, 
+                new Point3D { X = l, Y = 0.0, Z = testZ },
+                new Point3D { X = 3.0, Y = 0.0, Z = 7.7 },
+            });
+
+            // Call
+            var result = surfaceLine.GetZAtL(l);
+
+            // Assert
+            Assert.AreEqual(testZ, result);
+        }
+
+        [Test]
+        public void GetZAtL_SurfaceLineVerticalAtL_ThrowsRingtoetsPipingSurfaceLineException()
+        {
+            // Setup
+            var testZ = new Random(22).NextDouble();
+
+            var surfaceLine = new RingtoetsPipingSurfaceLine();
+            var l = 2.0;
+            surfaceLine.SetGeometry(new[]
+            {
+                new Point3D { X = 0.0, Y = 0.0, Z = 2.2 }, 
+                new Point3D { X = l, Y = 0.0, Z = testZ },
+                new Point3D { X = l, Y = 0.0, Z = testZ+1 },
+                new Point3D { X = 3.0, Y = 0.0, Z = 7.7 },
+            });
+
+            // Call
+            TestDelegate test = () => surfaceLine.GetZAtL(l);
+
+            // Assert
+            var exception = Assert.Throws<RingtoetsPipingSurfaceLineException>(test);
+            var message = string.Format(Properties.Resources.RingtoetsPipingSurfaceLine_Cannot_determine_reliable_z_when_surface_line_is_vertical_in_l, l);
+            Assert.AreEqual(message, exception.Message);
+        }
+
+        [Test]
         public void ToString_ReturnName()
         {
             // Setup
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Segment2DTest.cs
===================================================================
diff -u -rf69d756f50ae1464a1a11f0780b6d6aa646f3114 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Segment2DTest.cs	(.../Segment2DTest.cs)	(revision f69d756f50ae1464a1a11f0780b6d6aa646f3114)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/Segment2DTest.cs	(.../Segment2DTest.cs)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -84,6 +84,37 @@
         }
 
         [Test]
+        [TestCase(1e-9, false)]
+        [TestCase(1e-8 + 1e-10, true)]
+        [TestCase(1e-8 - 1e-10, false)]
+        [TestCase(1e-7, true)]
+        [TestCase(1, true)]
+        public void IsVertical_DifferencesInY_ReturnsExpectedValue(double difference, bool isVertical)
+        {
+            // Setup
+            var random = new Random(22);
+            var x = random.NextDouble();
+            var y = random.NextDouble();
+            var firstPoint = new Point2D
+            {
+                X = x,
+                Y = y
+            };
+            var secondPoint = new Point2D
+            {
+                X = x,
+                Y = y+difference
+            };
+            var segment = new Segment2D(firstPoint, secondPoint);
+
+            // Call
+            var result = segment.IsVertical();
+
+            // Assert
+            Assert.AreEqual(isVertical, result);
+        }
+
+        [Test]
         public void Equals_SameSegment_ReturnsTrue()
         {
             // Setup
Fisheye: Tag 712a020ea0330ece24849c2710641c1ce399ed61 refers to a dead (removed) revision in file `Ringtoets/Piping/test/Ringtoets.Piping.IO.Test/Calculation/Math2DTest.cs'.
Fisheye: No comparison available.  Pass `N' to diff?
Index: Ringtoets/Piping/test/Ringtoets.Piping.IO.Test/Ringtoets.Piping.IO.Test.csproj
===================================================================
diff -u -ra6ba313236d0ff8d2f219fc8249b700b1eade338 -r712a020ea0330ece24849c2710641c1ce399ed61
--- Ringtoets/Piping/test/Ringtoets.Piping.IO.Test/Ringtoets.Piping.IO.Test.csproj	(.../Ringtoets.Piping.IO.Test.csproj)	(revision a6ba313236d0ff8d2f219fc8249b700b1eade338)
+++ Ringtoets/Piping/test/Ringtoets.Piping.IO.Test/Ringtoets.Piping.IO.Test.csproj	(.../Ringtoets.Piping.IO.Test.csproj)	(revision 712a020ea0330ece24849c2710641c1ce399ed61)
@@ -53,7 +53,6 @@
     <Compile Include="Builders\SoilProfileBuilder1DTest.cs" />
     <Compile Include="Builders\SoilProfileBuilder2DTest.cs" />
     <Compile Include="Builders\SoilProfileBuilderExceptionTest.cs" />
-    <Compile Include="Calculation\Math2DTest.cs" />
     <Compile Include="Exceptions\CriticalFileReadExceptionTest.cs" />
     <Compile Include="Exceptions\LineParseExceptionTest.cs" />
     <Compile Include="Exceptions\PipingSoilProfileReadExceptionTest.cs" />