diff --git a/gtsam_unstable/geometry/Similarity3.cpp b/gtsam_unstable/geometry/Similarity3.cpp
index 819c51fee..8e3e97067 100644
--- a/gtsam_unstable/geometry/Similarity3.cpp
+++ b/gtsam_unstable/geometry/Similarity3.cpp
@@ -24,7 +24,7 @@
 namespace gtsam {
 
 using std::vector;
-using PointPairs = vector<Point3Pair>;
+typedef PointPairs = vector<Point3Pair>;
 
 namespace {
 /// Subtract centroids from point pairs.
diff --git a/gtsam_unstable/gtsam_unstable.i b/gtsam_unstable/gtsam_unstable.i
index b5d9133cd..1ca73bbe6 100644
--- a/gtsam_unstable/gtsam_unstable.i
+++ b/gtsam_unstable/gtsam_unstable.i
@@ -164,12 +164,23 @@ class BearingS2 {
 };
 
 #include <gtsam_unstable/geometry/Similarity3.h>
+class PointPairs
+{
+  PointPairs();
+  size_t size() const;
+  bool empty() const;
+  gtsam::Point3Pair at(size_t n) const;
+  void push_back(const gtsam::Point3Pair& point_pair);
+};
+
 class Similarity3 {
   Similarity3();
   Similarity3(double s);
   Similarity3(const gtsam::Rot3& R, const gtsam::Point3& t, double s);
   Similarity3(const Matrix& R, const Vector& t, double s);
   Similarity3(const Matrix& T);
+
+  static Similarity3 Align(const gtsam::PointPairs & abPointPairs);
 };
   
 #include <gtsam_unstable/geometry/SimWall2D.h>
diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index b50701464..3d6bf1702 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -41,6 +41,7 @@ set(ignore
     gtsam::BetweenFactorPose2s
     gtsam::BetweenFactorPose3s
     gtsam::Point2Vector
+    gtsam::PointPairs
     gtsam::Pose3Vector
     gtsam::KeyVector
     gtsam::BinaryMeasurementsUnit3
diff --git a/python/gtsam/specializations.h b/python/gtsam/specializations.h
index 431697aac..04c1aa82c 100644
--- a/python/gtsam/specializations.h
+++ b/python/gtsam/specializations.h
@@ -6,6 +6,7 @@ py::bind_vector<std::vector<gtsam::Key, tbb::tbb_allocator<gtsam::Key> > >(m_, "
 py::bind_vector<std::vector<gtsam::Key> >(m_, "KeyVector");
 #endif
 py::bind_vector<std::vector<gtsam::Point2, Eigen::aligned_allocator<gtsam::Point2> > >(m_, "Point2Vector");
+py::bind_vector<std::vector<gtsam::Point3Pair> >(m_, "PointPairs");
 py::bind_vector<std::vector<gtsam::Pose3> >(m_, "Pose3Vector");
 py::bind_vector<std::vector<boost::shared_ptr<gtsam::BetweenFactor<gtsam::Pose3> > > >(m_, "BetweenFactorPose3s");
 py::bind_vector<std::vector<boost::shared_ptr<gtsam::BetweenFactor<gtsam::Pose2> > > >(m_, "BetweenFactorPose2s");