Class MovementDetectorPos

• Defined in File MovementDetectorPos.hpp

Inheritance Relationships

Base Type

• public navtk::inertial::MovementDetectorPlugin (Class MovementDetectorPlugin)

Class Documentation

class MovementDetectorPos : public navtk::inertial::MovementDetectorPlugin

Accepts position data and attempts to detect movement based on delta positions.

Public Functions

MovementDetectorPos(const double speed_cutoff = 0.2, const double zero_corr_distance = 100.0)

Constructor.

See also

process(). Minimum value is 1, and anything less will be silently replaced.

Parameters

• speed_cutoff – Nominal speed threshold for platform to be considered moving, in m/s. Speed in all axes must be below this value to be classified as stationary over the period between 2 position inputs.

• zero_corr_distance – Threshold distance between two sequential position measurements at which they are considered uncorrelated, in m. Correlation between the the two measurements is linearly scaled based on the norm distance between the two points;

virtual MovementStatus process(not_null<std::shared_ptr<aspn_xtensor::AspnBase>> data) override

Add another position measurement and possibly update status.

When a new measurement is received, the NED speed is calculated and if under speed_cutoff in all axes status is set to MovementStatus::NOT_MOVING. Otherwise, the delta position is compared to the covariance of the difference measurements. If the change in position in any single axis is greater than the 3 sigma bounds, status is set to MovementStatus::MOVING. For all other cases status is set to MovementStatus::POSSIBLY_MOVING. The covariance of the differenced measurements is calculated as

\( \sigma_{diff}^2 = \sigma^2_{k-1} + \sigma^2_{k} - 2 \rho \sigma_{k - 1} \sigma_{k} \)

where \( \rho \), the correlation coefficient, is

\( 1 - \frac{\left|\Delta p_{k-1, k}\right|}{z} \)

and \( z \) is the value of the zero_corr_distance constructor parameter.

Parameters

data – Position measurement to process. Must dynamic cast to a MeasurementPosition or will be ignored.

Returns

Best estimate of movement status based on the last 2 measurements received. If data is tagged with a time earlier than the last measurement received (defined as a dt < 1e-20), a warning will be generated, or an error thrown, depending on the value of navtk::ErrorMode.

virtual aspn_xtensor::TypeTimestamp get_time() override

Time of last measurement received.

Returns

Last time; to_type_timestamp(0, 0) if no measurements yet received.