Copter: rename WP_TKOFF_NAV_ALT to WP_NAVALT_MIN

this is in preparation for using the same parameter for landing as
well

ArduCopter/Parameters.cpp

@@ -963,12 +963,12 @@ const AP_Param::Info Copter::var_info[] = {
  */
 const AP_Param::GroupInfo ParametersG2::var_info[] = {
 
-    // @Param: TKOFF_NAV_ALT
-    // @DisplayName: Takeoff navigation altitude
-    // @Description: This is the altitude in meters above the takeoff point that attitude changes for navigation can begin
+    // @Param: WP_NAVALT_MIN
+    // @DisplayName: Minimum navigation altitude
+    // @Description: This is the altitude in meters above which for navigation can begin. This applies in auto takeoff and auto landing.
     // @Range: 0 5
     // @User: Standard
-    AP_GROUPINFO("WP_TKOFF_NAV_ALT", 1, ParametersG2, takeoff_nav_alt, 0),
+    AP_GROUPINFO("WP_NAVALT_MIN", 1, ParametersG2, wp_navalt_min, 0),
 
     // @Group: BTN_
     // @Path: ../libraries/AP_Button/AP_Button.cpp

ArduCopter/Parameters.h

@@ -546,7 +546,7 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
     // altitude at which nav control can start in takeoff
-    AP_Float takeoff_nav_alt;
+    AP_Float wp_navalt_min;
 
     // button checking
     AP_Button button;

ArduCopter/control_auto.cpp

@@ -139,7 +139,7 @@ void Copter::auto_takeoff_start(const Location& dest_loc)
     // clear i term when we're taking off
     set_throttle_takeoff();
 
-    // get initial alt for TKOFF_NAV_ALT
+    // get initial alt for WP_NAVALT_MIN
     auto_takeoff_set_start_alt();
 }
 

ArduCopter/control_guided.cpp

@@ -74,7 +74,7 @@ bool Copter::guided_takeoff_start(float final_alt_above_home)
     // clear i term when we're taking off
     set_throttle_takeoff();
 
-    // get initial alt for WP_TKOFF_NAV_ALT
+    // get initial alt for WP_NAVALT_MIN
     auto_takeoff_set_start_alt();
     
     return true;

ArduCopter/takeoff.cpp

@@ -150,21 +150,21 @@ void Copter::auto_takeoff_set_start_alt(void)
     auto_takeoff_no_nav_alt_cm = inertial_nav.get_altitude();
     
     if (!motors.armed() || !ap.auto_armed || !motors.get_interlock() || ap.land_complete) {
-        // we are not flying, add the takeoff_nav_alt
-        auto_takeoff_no_nav_alt_cm += g2.takeoff_nav_alt * 100;
+        // we are not flying, add the wp_navalt_min
+        auto_takeoff_no_nav_alt_cm += g2.wp_navalt_min * 100;
     }
 }
 
 
 /*
   call attitude controller for automatic takeoff, limiting roll/pitch
-  if below takeoff_nav_alt
+  if below wp_navalt_min
  */
 void Copter::auto_takeoff_attitude_run(float target_yaw_rate)
 {
     float nav_roll, nav_pitch;
     
-    if (g2.takeoff_nav_alt > 0 && inertial_nav.get_altitude() < auto_takeoff_no_nav_alt_cm) {
+    if (g2.wp_navalt_min > 0 && inertial_nav.get_altitude() < auto_takeoff_no_nav_alt_cm) {
         // we haven't reached the takeoff navigation altitude yet
         nav_roll = 0;
         nav_pitch = 0;