Index: Ringtoets/Piping/src/Ringtoets.Piping.IO/Calculation/Math2D.cs
===================================================================
diff -u -r602479eb3666493485aee246d56b08958a6fc958 -rf69d756f50ae1464a1a11f0780b6d6aa646f3114
--- Ringtoets/Piping/src/Ringtoets.Piping.IO/Calculation/Math2D.cs	(.../Math2D.cs)	(revision 602479eb3666493485aee246d56b08958a6fc958)
+++ Ringtoets/Piping/src/Ringtoets.Piping.IO/Calculation/Math2D.cs	(.../Math2D.cs)	(revision f69d756f50ae1464a1a11f0780b6d6aa646f3114)
@@ -1,5 +1,6 @@
 using System;
 using Ringtoets.Piping.Data;
+using Ringtoets.Piping.IO.Properties;
 
 namespace Ringtoets.Piping.IO.Calculation
 {
@@ -11,36 +12,43 @@
         /// <summary>
         /// Constant which is used to precision errors in <see cref="double"/> comparisons.
         /// </summary>
-        public const double EpsilonForComparisons = 1e-8;
+        private const double epsilonForComparisons = 1e-8;
 
         /// <summary>
-        /// Determines the intersection point of a line which passes through the <paramref name="firstPoint"/> and 
-        /// the <paramref name="secondPoint"/>; and a line which passes through the <paramref name="thirdPoint"/>
-        /// and the <paramref name="fourthPoint"/>. When the lines are parallel, then <c>null</c> will be returned,
-        /// as no intersection point exists.
+        /// 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="firstPoint">A <see cref="Point2D"/> which the first line passes through.</param>
-        /// <param name="secondPoint">Another <see cref="Point2D"/> which the first line passes through.</param>
-        /// <param name="thirdPoint">A <see cref="Point2D"/> which the second line passes through.</param>
-        /// <param name="fourthPoint">Another <see cref="Point2D"/> which the second line passes through.</param>
+        /// <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>
-        public static Point2D LineIntersectionWithLine(Point2D firstPoint, Point2D secondPoint, Point2D thirdPoint, Point2D fourthPoint)
+        /// <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)
         {
-            var aLine = secondPoint.Y - firstPoint.Y;
-            var bLine = firstPoint.X - secondPoint.X;
-            var cLine = aLine*firstPoint.X + bLine*firstPoint.Y;
+            if (line1Point1.Equals(line1Point2) || line2Point1.Equals(line2Point2))
+            {
+                throw new ArgumentException(Resources.Math2D_LineIntersectionWithLine_Line_points_are_equal);
+            }
 
-            var aOtherLine = fourthPoint.Y - thirdPoint.Y;
-            var bOtherLine = thirdPoint.X - fourthPoint.X;
-            var cOtherLine = aOtherLine*thirdPoint.X + bOtherLine*thirdPoint.Y;
+            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)
+            if (Math.Abs(determinant) < epsilonForComparisons)
             {
                 return null;
             }