diff --git a/ellipsoide.py b/ellipsoide.py
index 1cf1a7d..a58e444 100644
--- a/ellipsoide.py
+++ b/ellipsoide.py
@@ -166,6 +166,22 @@ class EllipsoidTriaxial:
 
         return x, y, z
 
+    def ell2cart_P(self, lamb, beta):
+
+        """
+        Panou 2013, 241
+
+        :param lamb: ellipsoidische Länge
+        :param beta: reduzierte ellipsoidische Breite
+        :return: kartesische Koordinaten x y z
+        """
+
+        x = self.ax * np.sqrt(np.cos(beta) ** 2 + self.Ee ** 2 / self.Ex ** 2 * np.sin(beta) ** 2) * np.cos(lamb)
+        y = self.ay * np.cos(beta) * np.sin(lamb)
+        z = self.b * np.sin(beta) * np.sqrt(1 - self.Ee ** 2 / self.Ex ** 2 * np.cos(lamb) ** 2)
+
+        return x, y, z
+
     def cart2ell(self, x, y, z):
         """
         Panou 2014 15ff.