Struct Hold 

pub struct Hold {
    pub sigma: Meters,
}

The position hold an unaided filter fuses to keep its tilt. Equation (28″).

Without horizontal aiding nothing observes tilt, so a vehicle that loses GNSS in flight loses its attitude on the schedule ImuNoise sets while the true error may still be small. With no horizontal measurement judged within Timeouts::dead_reckoning_after, which a start that has heard none meets from its first step, no Eskf::fuse_stationary accepted, and the tilt σ past 3°, the filter fuses its own position estimate from the step the hold engaged, every 0.2 s at sigma. Bounding position bounds velocity, so a velocity error can no longer hide a tilt error, and the accelerometer levels the filter. PX4’s fake position (fake_pos_control.cpp:47-82 at c4e4ef98) and ArduPilot’s AID_NONE (AP_NavEKF3_Control.cpp:416-420 at 368dc0c4) do the same.

It assumes the vehicle stays near where the hold engaged. A hover meets that; a sustained acceleration reads as tilt error, and sigma is the trade between the two, which is the mission’s: how far a vehicle flies on without aiding is what it is flying for. A vehicle that keeps moving without GNSS, a car or a fixed-wing, should turn it off: on UrbanNav’s car the hold took the F9P’s position NEES from 1.02 to 32 (decision).

The hold is an assumption, not a sensor: Status stays DeadReckoning, and horizontal position and velocity each stay invalid in Validity, however tight the covariance the hold leaves, until a measurement of that quantity is accepted or adopted. A stationary claim, a fix the gate turns down or a velocity does not validate position; a stationary claim does bound velocity, and so does the second position fix the gate passes, which has checked the velocity that carried the estimate from the first. The first GNSS fix or velocity after it that the gate turns down is adopted at once rather than after Config::recovery’s timeout, since what the gate would be judging it against is the hold. A source whose recovery is off is never adopted. A caller’s reset_position_to or reset_velocity_to ends it for its quantity, until the hold next fuses. On by default, as Coast is; Config::hold = None is the opt-out.

Fields

sigma: Meters

The σ of the held position on each horizontal axis.

Trait Implementations

impl Clone for Hold

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Hold

impl Debug for Hold

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Hold

fn default() -> Self

PX4’s EKF2_NOAID_NOISE (src/modules/ekf2/module.yaml:67-75 at c4e4ef98) and ArduPilot’s EK3_NOAID_M_NSE (AP_NavEKF3.cpp:447-453 at 368dc0c4) both default to 10 m.

impl PartialEq for Hold

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Hold