Add solver for april tag mapping

Takes in robot locations (at control loop frequency), and less frequent
localizations off of april tags. Builds a graph of constraints between
subsequent target detections and solves for the optimal target locations
on the field.

Change-Id: I1256f5914b7656d9e14735f9d994572688c3aaa8
Signed-off-by: Milind Upadhyay <milind.upadhyay@gmail.com>
diff --git a/frc971/vision/ceres/angle_local_parameterization.h b/frc971/vision/ceres/angle_local_parameterization.h
new file mode 100644
index 0000000..a81637c
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+++ b/frc971/vision/ceres/angle_local_parameterization.h
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2016 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+//   used to endorse or promote products derived from this software without
+//   specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: vitus@google.com (Michael Vitus)
+
+#ifndef CERES_EXAMPLES_POSE_GRAPH_2D_ANGLE_LOCAL_PARAMETERIZATION_H_
+#define CERES_EXAMPLES_POSE_GRAPH_2D_ANGLE_LOCAL_PARAMETERIZATION_H_
+
+#include "ceres/local_parameterization.h"
+#include "normalize_angle.h"
+
+namespace ceres {
+namespace examples {
+
+// Defines a local parameterization for updating the angle to be constrained in
+// [-pi to pi).
+class AngleLocalParameterization {
+ public:
+  template <typename T>
+  bool operator()(const T* theta_radians,
+                  const T* delta_theta_radians,
+                  T* theta_radians_plus_delta) const {
+    *theta_radians_plus_delta =
+        NormalizeAngle(*theta_radians + *delta_theta_radians);
+
+    return true;
+  }
+
+  static ceres::LocalParameterization* Create() {
+    return (new ceres::AutoDiffLocalParameterization<AngleLocalParameterization,
+                                                     1,
+                                                     1>);
+  }
+};
+
+}  // namespace examples
+}  // namespace ceres
+
+#endif  // CERES_EXAMPLES_POSE_GRAPH_2D_ANGLE_LOCAL_PARAMETERIZATION_H_