diff --git a/src/rigidbodymotion.hh b/src/rigidbodymotion.hh
index 04ea26e93b46db3e30ea919ed7a1755ba5deec80..3247433a1a8b09de155e46b6e174046792bcb91e 100644
--- a/src/rigidbodymotion.hh
+++ b/src/rigidbodymotion.hh
@@ -8,6 +8,9 @@
 template <int dim, class ctype=double>
 struct RigidBodyMotion
 {
+    /** \brief Type of an infinitesimal rigid body motion */
+    typedef Dune::FieldVector<ctype, (dim==3) ? 6 : 3> TangentVector;
+
     // Translational part
     Dune::FieldVector<ctype, dim> r;
 
diff --git a/src/rotation.hh b/src/rotation.hh
index c632da95d2f4439a3a6e25562a120b62afa91333..c20900fa4959dc4c0a0ec43c5fe487a6523527b7 100644
--- a/src/rotation.hh
+++ b/src/rotation.hh
@@ -34,6 +34,9 @@ class Rotation<3,T> : public Quaternion<T>
 
 public:
 
+    /** \brief Member of the corresponding Lie algebra.  This really is a skew-symmetric matrix */
+    typedef Dune::FieldVector<T,3> TangentVector;
+
     /** \brief Default constructor creates the identity element */
     Rotation()
         : Quaternion<T>(0,0,0,1)