ardupilot/ArduCopter/navigation.cpp

#include "Copter.h"

// run_nav_updates - top level call for the autopilot
// ensures calculations such as "distance to waypoint" are calculated before autopilot makes decisions
// To-Do - rename and move this function to make it's purpose more clear
void Copter::run_nav_updates(void)
{
    // calculate distance and bearing for reporting and autopilot decisions
    calc_home_distance_and_bearing();

    flightmode->update_navigation();
}

// calc_home_distance_and_bearing - calculate distance and bearing to home for reporting and autopilot decisions
void Copter::calc_home_distance_and_bearing()
{
    // calculate home distance and bearing
    if (position_ok()) {
        Vector3f home = pv_location_to_vector(ahrs.get_home());
        Vector3f curr = inertial_nav.get_position();
        home_distance = get_horizontal_distance_cm(curr, home);
        home_bearing = get_bearing_cd(curr,home);

        // update super simple bearing (if required) because it relies on home_bearing
        update_super_simple_bearing(false);
    }
}