AC_PrecLand: small improvements in comments

libraries/AC_PrecLand/AC_PrecLand.cpp

@@ -93,7 +93,7 @@ const AP_Param::GroupInfo AC_PrecLand::var_info[] = {
 
     // @Param: LAG
     // @DisplayName: Precision Landing sensor lag
-    // @Description: Precision Landing sensor lag in ms, to cope with variable landing_target latency
+    // @Description: Precision Landing sensor lag, to cope with variable landing_target latency
     // @Range: 0.02 0.250
     // @Increment: 1
     // @Units: s
@@ -283,7 +283,7 @@ void AC_PrecLand::run_estimator(float rangefinder_alt_m, bool rangefinder_alt_va
                 _target_vel_rel_est_NE.y = -inertial_data_delayed->inertialNavVelocity.y;
             }
 
-            // Update if a new LOS measurement is available
+            // Update if a new Line-Of-Sight measurement is available
             if (construct_pos_meas_using_rangefinder(rangefinder_alt_m, rangefinder_alt_valid)) {
                 _target_pos_rel_est_NE.x = _target_pos_rel_meas_NED.x;
                 _target_pos_rel_est_NE.y = _target_pos_rel_meas_NED.y;
@@ -310,7 +310,7 @@ void AC_PrecLand::run_estimator(float rangefinder_alt_m, bool rangefinder_alt_va
                 _ekf_y.predict(dt, -vehicleDelVel.y, _accel_noise*dt);
             }
 
-            // Update if a new LOS measurement is available
+            // Update if a new Line-Of-Sight measurement is available
             if (construct_pos_meas_using_rangefinder(rangefinder_alt_m, rangefinder_alt_valid)) {
                 float xy_pos_var = sq(_target_pos_rel_meas_NED.z*(0.01f + 0.01f*AP::ahrs().get_gyro().length()) + 0.02f);
                 if (!target_acquired()) {

libraries/AC_PrecLand/AC_PrecLand.h

@@ -105,7 +105,7 @@ private:
     // run target position estimator
     void run_estimator(float rangefinder_alt_m, bool rangefinder_alt_valid);
 
-    // If a new measurement was retreived, sets _target_pos_rel_meas_NED and returns true
+    // If a new measurement was retrieved, sets _target_pos_rel_meas_NED and returns true
     bool construct_pos_meas_using_rangefinder(float rangefinder_alt_m, bool rangefinder_alt_valid);
 
     // get vehicle body frame 3D vector from vehicle to target.  returns true on success, false on failure
@@ -124,7 +124,7 @@ private:
     AP_Float                    _yaw_align;         // Yaw angle from body x-axis to sensor x-axis.
     AP_Float                    _land_ofs_cm_x;     // Desired landing position of the camera forward of the target in vehicle body frame
     AP_Float                    _land_ofs_cm_y;     // Desired landing position of the camera right of the target in vehicle body frame
-    AP_Float                    _accel_noise;       // accelometer process noise
+    AP_Float                    _accel_noise;       // accelerometer process noise
     AP_Vector3f                 _cam_offset;        // Position of the camera relative to the CG
 
     uint32_t                    _last_update_ms;    // system time in millisecond when update was last called

libraries/AC_PrecLand/AC_PrecLand_Companion.h

@@ -7,6 +7,8 @@
 /*
  * AC_PrecLand_Companion - implements precision landing using target vectors provided
  *                         by a companion computer (i.e. Odroid) communicating via MAVLink
+ *                         The companion computer must provide "Line-Of-Sight" measurements
+ *                         in the form of LANDING_TARGET mavlink messages.
  */
 
 class AC_PrecLand_Companion : public AC_PrecLand_Backend