observation.h

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#ifndef IMU_FILTER_OBSERVATION_H
#define IMU_FILTER_OBSERVATION_H

#include <ros/ros.h>
#include <Eigen/Geometry>
#include <imu_filter/imu_state.h>

namespace imu_filter
{
        //* Base class for EKF observation model
        class Observation
        {
                public:
                        static const size_t Dimension = 7;
                        typedef Eigen::Matrix<double, Dimension, 1> Vector;
                        typedef Eigen::Matrix<double, Dimension, Dimension> CovMat;
                        typedef Eigen::Matrix<double, Dimension, ImuState::Dimension> JacMat;

                        Observation() : 
                                observation_( Vector::Zero() ),
                                measCov_( CovMat::Zero() ),
                                measJacobian_( JacMat::Zero() ),
                                body2ImuTransform_( Eigen::Affine3d::Identity() ),
                                lastBodyTransform_( Eigen::Affine3d::Identity() ),
                                lastWorld2Imu_( Eigen::Affine3d::Identity() ),
                                deltaTransform_( Eigen::Affine3d::Identity() )
                        {
                        }

                        virtual ~Observation()
                        {
                        }

                        void set( const Vector & v ) { observation_ = v; }

                        const Vector & vector() const { return observation_; }

                        void setCovariance( const CovMat & covariance  ) { measCov_ = covariance; }

                        void setCovarianceFromStdDev( const Vector & stdDevs )
                        {
                                measCov_.setZero();
                                for( int i = 0; i < stdDevs.rows(); i++ )
                                        measCov_( i, i ) = utils::square( stdDevs[ i ] );
                        }

                        const CovMat & covariance() const { return measCov_; }
                        
                        const JacMat & jacobian() const { return measJacobian_; }

        
                        void setBody2ImuTransform( const Eigen::Quaterniond & q, const Eigen::Vector3d & t ) 
                        { 
                                body2ImuTransform_.linear() = q.toRotationMatrix();
                                body2ImuTransform_.translation() = t;
                        }

                        void setBody2ImuTransform( const Eigen::Affine3d & T ) { body2ImuTransform_ = T; }

                        const Eigen::Affine3d & body2ImuTransform() const { return body2ImuTransform_; }

                        void updateLastStateInformation( const ImuState & state )
                        {
                                lastWorld2Imu_.linear() = state.orientation().toRotationMatrix();
                                lastWorld2Imu_.translation() = state.position();
                        }

                        const Eigen::Affine3d & lastWorld2Imu() const { return lastWorld2Imu_; }

                        virtual void updateJacobian( const ImuState & state ) = 0;

                protected:
                        Vector  observation_;
                        CovMat  measCov_;
                        JacMat  measJacobian_;

                        Eigen::Affine3d         body2ImuTransform_;

                        Eigen::Affine3d         lastBodyTransform_;

                        // last state information of the IMU to create the pseudo measurement
                        Eigen::Affine3d         lastWorld2Imu_;

                        // delta transformation between last and current IMU frame, computed from last two full body transformations
                        Eigen::Affine3d         deltaTransform_;

                        // compute delta translation and delta position between last imu measures
                        void computeDeltaFromAbsolute( const Eigen::Affine3d & currentObservation )
                        {
                                // compute delta transformation of the IMU w.r.t. to the last measurements 
                                deltaTransform_ = body2ImuTransform_.inverse() * lastBodyTransform_.inverse() * currentObservation * body2ImuTransform_; 
                        }

                        void updateObservationFromDelta()
                        {
                                Eigen::Affine3d pseudoTrans     = lastWorld2Imu_ * deltaTransform_;

                                Eigen::Quaterniond pseudoQ;
                                pseudoQ = pseudoTrans.rotation();
                                pseudoQ.normalize();

                                observation_.head<4>() = pseudoQ.coeffs();
                                observation_.tail<3>() = pseudoTrans.translation();
                        }
        };

}

#endif