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added comments to imu preintegration

release/4.3a0
Luca 2014-11-12 19:06:16 -05:00
parent 1c97d1270d
commit c6c611ae11
1 changed files with 13 additions and 3 deletions
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16
gtsam/navigation/ImuFactor.h
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@ -58,7 +58,7 @@ namespace gtsam {
class PreintegratedMeasurements {
public:
imuBias::ConstantBias biasHat; ///< Acceleration and angular rate bias values used during preintegration
Matrix measurementCovariance; ///< (Raw measurements uncertainty) Covariance of the vector [integrationError measuredAcc measuredOmega] in R^(9X9)
Matrix measurementCovariance; ///< (continuous-time uncertainty) Covariance of the vector [integrationError measuredAcc measuredOmega] in R^(9X9)
Vector3 deltaPij; ///< Preintegrated relative position (does not take into account velocity at time i, see deltap+, in [2]) (in frame i)
Vector3 deltaVij; ///< Preintegrated relative velocity (in global frame)
@ -217,11 +217,21 @@ namespace gtsam {
H_vel_pos, H_vel_vel, H_vel_angles,
H_angles_pos, H_angles_vel, H_angles_angles;
// first order uncertainty propagation
// first order uncertainty propagation:
// the deltaT allows to pass from continuous time noise to discrete time noise
// measurementCovariance_discrete = measurementCovariance_contTime * (1/deltaT)
// Gt * Qt * G =(approx)= measurementCovariance_discrete * deltaT^2 = measurementCovariance_contTime * deltaT
PreintMeasCov = F * PreintMeasCov * F.transpose() + measurementCovariance * deltaT ;
// Extended version, without approximation: Gt * Qt * G =(approx)= measurementCovariance_contTime * deltaT
//
// Matrix G(9,9);
// G << I_3x3 * deltaT, Z_3x3, Z_3x3,
// Z_3x3, deltaRij.matrix() * deltaT, Z_3x3,
// Z_3x3, Z_3x3, Jrinv_theta_j * Jr_theta_incr * deltaT;
//
// PreintMeasCov = F * PreintMeasCov * F.transpose() + G * (1/deltaT) * measurementCovariance * G.transpose();
// Update preintegrated measurements
/* ----------------------------------------------------------------------------------------------------------------------- */
if(!use2ndOrderIntegration_){