GPS Navigation

The GPS Navigation tab configures GPS RTH and Loiter -- the fixed-wing navigation controller behind both, and behind the Failsafe tab's GPS Rescue procedure too. It only appears once GPS is active, which means the GPS Protocol on the GPS tab matches a port (see When GPS is active).

These settings used to be CLI-only, then briefly lived on the Failsafe tab; they moved here because they aren't failsafe-specific -- GPS RTH and GPS LOITER (whether switched on by hand or started by the Failsafe tab's GPS Rescue procedure) all use them.

Arming without a GPS fix

When the Failsafe tab's GPS Rescue procedure or a GPS RTH switch is set up, the first arm after power-up is blocked until the GPS has a fix (the GPS arming disable flag). Re-arming later in the same power cycle doesn't need one.

If you can't get a lock at the field, turn on Allow arming without GPS fix (gps_rescue_allow_arming_without_fix, default OFF) at the top of this tab. On the radio it is Arm w/o GPS Fix on the Lua suite's GPS Navigation page.

The home point is only recorded at arming, with a fix and at least 5 satellites, so a flight armed without a fix has no home, even if the GPS locks later:

• A GPS Rescue failsafe falls back to self-leveling with the motor off, like Land/Drop, instead of flying home.
• The GPS RTH switch flies level and doesn't turn toward home.
• GPS LOITER still works once a fix arrives, since it orbits where it was switched on.

Turn the setting off again once GPS is working, so the arming check protects your next flights.

Settings

Field	Setting	Default	Meaning
RTH Altitude	nav_rth_altitude	50m	Altitude RTH climbs or descends toward
Loiter Radius	nav_loiter_radius	75m	Orbit radius for GPS LOITER
Loiter Direction	nav_loiter_direction	CW	Orbit direction, clockwise or counter-clockwise
Min Satellites	nav_min_sats	6	Minimum satellite count for navigation to run. Once navigating, one fewer is tolerated, and short dropouts are ridden through (see GPS RTH and Loiter)
Max Bank Angle	nav_max_bank_angle	25°	Largest bank the navigation commands
Max Pitch Angle	nav_max_pitch_angle	15°	Largest pitch the navigation commands

Two more, under Expert:

Field	Setting	Default	Meaning
Bearing Gain	nav_bearing_kp	200	Bank per degree of course error, percent
Altitude Gain	nav_altitude_kp	100	Pitch per metre of altitude error, percent

See GPS RTH and Loiter for how these are actually used, their defaults' practical effect, and known limits -- this tab is just where you set them. Home point capture (when RTH's "home" is recorded) is a GPS tab setting, not one of these.