--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/geom/Lines.java	Fri May 11 07:24:12 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/geom/Lines.java	Fri May 11 08:45:11 2012 +0000
@@ -35,15 +35,13 @@
      * @return area of polygon with four vertices.
      */
     public static double area(Point2D p1, Point2D p2, Point2D p3, Point2D p4) {
-        double[] x = new double[] {p1.getX(), p2.getX(), p3.getX(), p4.getX() };
-        double[] y = new double[] {p1.getY(), p2.getY(), p3.getY(), p4.getY() };
+        double[] x = new double[] {p1.getX(), p2.getX(), p3.getX(), p4.getX(), p1.getX() };
+        double[] y = new double[] {p1.getY(), p2.getY(), p3.getY(), p4.getY(), p1.getY() };
         double area = 0d;
-        int j = 3;
         for (int i=0; i <4; i++) {
-            area += (x[j] + x[i]) * (y[j] - y[i]);
-            j = i;
+            area += (x[i] * y[i+1]) - (x[i+1] * y[i]);
         }
-        return area * 0.5d;
+        return Math.abs(area * 0.5d);
     }