diff --git a/gtsam_unstable/slam/MagPoseFactor.h b/gtsam_unstable/slam/MagPoseFactor.h new file mode 100644 index 0000000000..da2a54ce99 --- /dev/null +++ b/gtsam_unstable/slam/MagPoseFactor.h @@ -0,0 +1,141 @@ +/* ---------------------------------------------------------------------------- + + * GTSAM Copyright 2010, Georgia Tech Research Corporation, + * Atlanta, Georgia 30332-0415 + * All Rights Reserved + * Authors: Frank Dellaert, et al. (see THANKS for the full author list) + + * See LICENSE for the license information + + * -------------------------------------------------------------------------- */ + +#pragma once + +#include +#include + +namespace gtsam { + +/** + * Factor to estimate rotation of a Pose2 or Pose3 given a magnetometer reading. + * This version uses the measurement model bM = scale * bRn * direction + bias, + * where bRn is the rotation of the body in the nav frame, and scale, direction, + * and bias are assumed to be known. If the factor is constructed with a + * body_P_sensor, then the magnetometer measurements and bias should be + * expressed in the sensor frame. + */ +template +class MagPoseFactor: public NoiseModelFactor1 { + private: + using This = MagPoseFactor; + using Base = NoiseModelFactor1; + using Point = typename POSE::Translation; ///< Could be a Vector2 or Vector3 depending on POSE. + using Rot = typename POSE::Rotation; + + const Point measured_; ///< The measured magnetometer data in the body frame. + const Point nM_; ///< Local magnetic field (mag output units) in the nav frame. + const Point bias_; ///< The bias vector (mag output units) in the body frame. + boost::optional body_P_sensor_; ///< The pose of the sensor in the body frame. + + static const int MeasDim = Point::RowsAtCompileTime; + static const int PoseDim = traits::dimension; + static const int RotDim = traits::dimension; + + /// Shorthand for a smart pointer to a factor. + using shared_ptr = boost::shared_ptr>; + + /// Concept check by type. + GTSAM_CONCEPT_TESTABLE_TYPE(POSE) + GTSAM_CONCEPT_POSE_TYPE(POSE) + + public: + ~MagPoseFactor() override {} + + /// Default constructor - only use for serialization. + MagPoseFactor() {} + + /** + * Construct the factor. + * @param pose_key of the unknown pose nPb in the factor graph + * @param measured magnetometer reading, a Point2 or Point3 + * @param scale by which a unit vector is scaled to yield a magnetometer reading + * @param direction of the local magnetic field, see e.g. http://www.ngdc.noaa.gov/geomag-web/#igrfwmm + * @param bias of the magnetometer, modeled as purely additive (after scaling) + * @param model of the additive Gaussian noise that is assumed + * @param body_P_sensor an optional transform of the magnetometer in the body frame + */ + MagPoseFactor(Key pose_key, + const Point& measured, + double scale, + const Point& direction, + const Point& bias, + const SharedNoiseModel& model, + const boost::optional& body_P_sensor) + : Base(model, pose_key), + measured_(body_P_sensor ? body_P_sensor->rotation() * measured : measured), + nM_(scale * direction.normalized()), + bias_(body_P_sensor ? body_P_sensor->rotation() * bias : bias), + body_P_sensor_(body_P_sensor) {} + + /// @return a deep copy of this factor. + NonlinearFactor::shared_ptr clone() const override { + return boost::static_pointer_cast( + NonlinearFactor::shared_ptr(new This(*this))); + } + + /// Implement functions needed for Testable. + + // Print out the factor. + void print(const std::string& s = "", const KeyFormatter& keyFormatter = DefaultKeyFormatter) const override { + Base::print(s, keyFormatter); + gtsam::print(Vector(nM_), "local field (nM): "); + gtsam::print(Vector(measured_), "measured field (bM): "); + gtsam::print(Vector(bias_), "magnetometer bias: "); + } + + /// Equals function. + bool equals(const NonlinearFactor& expected, double tol=1e-9) const override { + const This *e = dynamic_cast (&expected); + return e != nullptr && Base::equals(*e, tol) && + gtsam::equal_with_abs_tol(this->measured_, e->measured_, tol) && + gtsam::equal_with_abs_tol(this->nM_, e->nM_, tol) && + gtsam::equal_with_abs_tol(this->bias_, e->bias_, tol); + } + + /// Implement functions needed to derive from Factor. + + /** + * Return the factor's error h(x) - z, and the optional Jacobian. Note that + * the measurement error is expressed in the body frame. + */ + Vector evaluateError(const POSE& nPb, boost::optional H = boost::none) const override { + // Predict the measured magnetic field h(x) in the *body* frame. + // If body_P_sensor was given, bias_ will have been rotated into the body frame. + Matrix H_rot = Matrix::Zero(MeasDim, RotDim); + const Point hx = nPb.rotation().unrotate(nM_, H_rot, boost::none) + bias_; + + if (H) { + // Fill in the relevant part of the Jacobian (just rotation columns). + *H = Matrix::Zero(MeasDim, PoseDim); + const size_t rot_col0 = nPb.rotationInterval().first; + (*H).block(0, rot_col0, MeasDim, RotDim) = H_rot; + } + + return (hx - measured_); + } + + private: + /// Serialization function. + friend class boost::serialization::access; + template + void serialize(ARCHIVE & ar, const unsigned int /*version*/) { + ar & boost::serialization::make_nvp("NoiseModelFactor1", + boost::serialization::base_object(*this)); + ar & BOOST_SERIALIZATION_NVP(measured_); + ar & BOOST_SERIALIZATION_NVP(nM_); + ar & BOOST_SERIALIZATION_NVP(bias_); + ar & BOOST_SERIALIZATION_NVP(body_P_sensor_); + } +}; // \class MagPoseFactor + +} /// namespace gtsam diff --git a/gtsam_unstable/slam/tests/testMagPoseFactor.cpp b/gtsam_unstable/slam/tests/testMagPoseFactor.cpp new file mode 100644 index 0000000000..7cfe74df21 --- /dev/null +++ b/gtsam_unstable/slam/tests/testMagPoseFactor.cpp @@ -0,0 +1,126 @@ +/* ---------------------------------------------------------------------------- + + * GTSAM Copyright 2010, Georgia Tech Research Corporation, + * Atlanta, Georgia 30332-0415 + * All Rights Reserved + * Authors: Frank Dellaert, et al. (see THANKS for the full author list) + + * See LICENSE for the license information + + * -------------------------------------------------------------------------- */ + +#include +#include +#include +#include +#include +#include +#include + +using namespace gtsam; + +// ***************************************************************************** +// Magnetic field in the nav frame (NED), with units of nT. +Point3 nM(22653.29982, -1956.83010, 44202.47862); + +// Assumed scale factor (scales a unit vector to magnetometer units of nT). +double scale = 255.0 / 50000.0; + +// Ground truth Pose2/Pose3 in the nav frame. +Pose3 n_P3_b = Pose3(Rot3::Yaw(-0.1), Point3(-3, 12, 5)); +Pose2 n_P2_b = Pose2(Rot2(-0.1), Point2(-3, 12)); +Rot3 n_R3_b = n_P3_b.rotation(); +Rot2 n_R2_b = n_P2_b.rotation(); + +// Sensor bias (nT). +Point3 bias3(10, -10, 50); +Point2 bias2 = bias3.head(2); + +Point3 dir3(nM.normalized()); +Point2 dir2(nM.head(2).normalized()); + +// Compute the measured field in the sensor frame. +Point3 measured3 = n_R3_b.inverse() * (scale * dir3) + bias3; + +// The 2D magnetometer will measure the "NE" field components. +Point2 measured2 = n_R2_b.inverse() * (scale * dir2) + bias2; + +SharedNoiseModel model2 = noiseModel::Isotropic::Sigma(2, 0.25); +SharedNoiseModel model3 = noiseModel::Isotropic::Sigma(3, 0.25); + +// Make up a rotation and offset of the sensor in the body frame. +Pose2 body_P2_sensor(Rot2(-0.30), Point2(1.0, -2.0)); +Pose3 body_P3_sensor(Rot3::RzRyRx(Vector3(1.5, 0.9, -1.15)), Point3(-0.1, 0.2, 0.3)); +// ***************************************************************************** + +// ***************************************************************************** +TEST(MagPoseFactor, Constructors) { + MagPoseFactor f2a(Symbol('X', 0), measured2, scale, dir2, bias2, model2, boost::none); + MagPoseFactor f3a(Symbol('X', 0), measured3, scale, dir3, bias3, model3, boost::none); + + // Try constructing with a body_P_sensor set. + MagPoseFactor f2b = MagPoseFactor( + Symbol('X', 0), measured2, scale, dir2, bias2, model2, body_P2_sensor); + MagPoseFactor f3b = MagPoseFactor( + Symbol('X', 0), measured3, scale, dir3, bias3, model3, body_P3_sensor); + + f2b.print(); + f3b.print(); +} + +// ***************************************************************************** +TEST(MagPoseFactor, JacobianPose2) { + Matrix H2; + + // Error should be zero at the groundtruth pose. + MagPoseFactor f(Symbol('X', 0), measured2, scale, dir2, bias2, model2, boost::none); + CHECK(gtsam::assert_equal(Z_2x1, f.evaluateError(n_P2_b, H2), 1e-5)); + CHECK(gtsam::assert_equal(gtsam::numericalDerivative11 // + (boost::bind(&MagPoseFactor::evaluateError, &f, _1, boost::none), n_P2_b), H2, 1e-7)); +} + +// ***************************************************************************** +TEST(MagPoseFactor, JacobianPose3) { + Matrix H3; + + // Error should be zero at the groundtruth pose. + MagPoseFactor f(Symbol('X', 0), measured3, scale, dir3, bias3, model3, boost::none); + CHECK(gtsam::assert_equal(Z_3x1, f.evaluateError(n_P3_b, H3), 1e-5)); + CHECK(gtsam::assert_equal(gtsam::numericalDerivative11 // + (boost::bind(&MagPoseFactor::evaluateError, &f, _1, boost::none), n_P3_b), H3, 1e-7)); +} + +// ***************************************************************************** +TEST(MagPoseFactor, body_P_sensor2) { + Matrix H2; + + // Because body_P_sensor is specified, we need to rotate the raw measurement + // from the body frame into the sensor frame "s". + const Rot2 nRs = n_R2_b * body_P2_sensor.rotation(); + const Point2 sM = nRs.inverse() * (scale * dir2) + bias2; + MagPoseFactor f = MagPoseFactor(Symbol('X', 0), sM, scale, dir2, bias2, model2, body_P2_sensor); + CHECK(gtsam::assert_equal(Z_2x1, f.evaluateError(n_P2_b, H2), 1e-5)); + CHECK(gtsam::assert_equal(gtsam::numericalDerivative11 // + (boost::bind(&MagPoseFactor::evaluateError, &f, _1, boost::none), n_P2_b), H2, 1e-7)); +} + +// ***************************************************************************** +TEST(MagPoseFactor, body_P_sensor3) { + Matrix H3; + + // Because body_P_sensor is specified, we need to rotate the raw measurement + // from the body frame into the sensor frame "s". + const Rot3 nRs = n_R3_b * body_P3_sensor.rotation(); + const Point3 sM = nRs.inverse() * (scale * dir3) + bias3; + MagPoseFactor f = MagPoseFactor(Symbol('X', 0), sM, scale, dir3, bias3, model3, body_P3_sensor); + CHECK(gtsam::assert_equal(Z_3x1, f.evaluateError(n_P3_b, H3), 1e-5)); + CHECK(gtsam::assert_equal(gtsam::numericalDerivative11 // + (boost::bind(&MagPoseFactor::evaluateError, &f, _1, boost::none), n_P3_b), H3, 1e-7)); +} + +// ***************************************************************************** +int main() { + TestResult tr; + return TestRegistry::runAllTests(tr); +} +// *****************************************************************************