Clarify RTL overview wording for pre-arm GPS and position checks

jinmussj · Hwurzburg · commit 97b4c53711be · 2026-04-22T06:16:49.000-05:00
The previous text could be read as an unconditional guarantee that default pre-arm checks always ensure a 3D GPS lock with sufficient HDOP and a working compass before arming. In practice, the exact arming and pre-arm gating depends on the selected mode and configuration. 

For example, arming in Stabilize can still be allowed under GPS/HDOP conditions that would not be accepted for a position-dependent mode.
diff --git a/copter/source/docs/rtl-mode.rst b/copter/source/docs/rtl-mode.rst
@@ -23,7 +23,7 @@ The altitude reference frame is set by either the rally point, if proceeding to
 
 If RTL is entered close to its return point, the altitude Copter climbs to may be limited to avoid unneeded climbs and descents. The :ref:`RTL_CONE_SLOPE<RTL_CONE_SLOPE>` parameter determines the slope of an inverted cone centered on the return point. This reduces the above return altitude according to: distance from return point * :ref:`RTL_CONE_SLOPE<RTL_CONE_SLOPE>`. So if the mode is entered 10m from the return point, using the default slope of "3", then the altitude rise would be limited to 30m before returning. It may be less depending on the other parameters, but not higher. If the slope were set to "0.5", then the initial climb would be no higher than 5m altitude before proceeding to the return point. A value of "0" disables this limit. "0.5" is the minimum slope. Again, 2m is the minimum return altitude.
 
-RTL mode requires a reliable position estimate to work properly, most commonly provided by GPS and compass. Default prearm checks will ensure a 3D GPS lock with sufficient HDOP is acquired and your mag is working as expected prior to arming. When using non-default arming checks, make sure you do have a sufficient GPS lock and / or a reliable position estimate for RTL to perform as expected.
+RTL mode requires a reliable position estimate to work properly, most commonly provided by GPS and compass. Default prearm checks will ensure a 3D GPS lock with sufficient HDOP is acquired and your mag is working as expected prior to arming, when required by the selected mode and configuration. When using non-default arming checks, make sure you do have a sufficient GPS lock and / or a reliable position estimate for RTL to perform as expected.
 
 
 RTL will command the copter to return to the home position, meaning that
