So instead of updating plane.guided_WP_loc and then calling
set_guided_WP(void) to copy that state into plane.next_WP_loc we pass
the new location in the call to set_guided_WP(const Location &loc).
avoidance was the only place which was not entirely over-writing
plane.guided_WP_loc. However, plane.next_WP_loc was updated to be the
current location when we entered guided mode. If we update the
horizontal/vertical avoidance now it is relative to the current
location, not the guided wp location, which could be quite important.
when we switch away from the blended GPS instance we need to ensure we
don't switch to a GPS that is timing out, and may be the instance that
is triggering the disable of blending
this improves 4 things in the POSITION1 controller based on logs from
4.2.0beta2. The changes are designed to increase the tolerance to
an incorrect value for Q_TRANS_DECEL, reducing landing overshoot
1) we fix the initialisation of the acceleration. The
init_xy_controller() function assumes zero accel, so we need to
call set_accel_desired_xy_cmss() just after that init to get the
correct accel. Thanks to Leonard for this fix
2) if we decel more than expected due to too low Q_TRANS_DECEL we
need to reduce the target speed, rather than putting the nose down
3) lower the default Q_P_JERK_XY to a value more appropriate for most
quadplanes (Leonard suggested a value of 2)
4) fixed the pitch envelope from Q_BACKTRANS_MS to start after the
airbrake phase is complete
we need to setup last_fw_mode_ms and last_fw_nav_pitch_cd when we
enter POSITION1 mode so that the expanding envelope pitch limit from
Q_BACKTRANS_MS is applied correctly