Merge branch 'master' of https://github.com/PX4/Firmware into vtol_merge

src/modules/uORB/topics/home_position.h

@@ -61,7 +61,7 @@ struct home_position_s
 
 	double lat;				/**< Latitude in degrees 			*/
 	double lon;				/**< Longitude in degrees			*/
-	float alt;				/**< Altitude in meters				*/
+	float alt;				/**< Altitude in meters	(AMSL)		*/
 
 	float x;				/**< X coordinate in meters			*/
 	float y;				/**< Y coordinate in meters			*/

src/modules/uORB/topics/mission.h

@@ -83,7 +83,7 @@ struct mission_item_s {
 	bool altitude_is_relative;	/**< true if altitude is relative from start point	*/
 	double lat;			/**< latitude in degrees				*/
 	double lon;			/**< longitude in degrees				*/
-	float altitude;			/**< altitude in meters					*/
+	float altitude;			/**< altitude in meters	(AMSL)			*/
 	float yaw;			/**< in radians NED -PI..+PI, NAN means don't change yaw		*/
 	float loiter_radius;		/**< loiter radius in meters, 0 for a VTOL to hover     */
 	int8_t loiter_direction;	/**< 1: positive / clockwise, -1, negative.		*/

src/modules/uORB/topics/vehicle_command.h

@@ -65,7 +65,7 @@ enum VEHICLE_CMD {
 	VEHICLE_CMD_NAV_TAKEOFF = 22, /* Takeoff from ground / hand |Minimum pitch (if airspeed sensor present), desired pitch without sensor| Empty| Empty| Yaw angle (if magnetometer present), ignored without magnetometer| Latitude| Longitude| Altitude|  */
 	VEHICLE_CMD_NAV_ROI = 80, /* Sets the region of interest (ROI) for a sensor set or the vehicle itself. This can then be used by the vehicles control system to control the vehicle attitude and the attitude of various sensors such as cameras. |Region of intereset mode. (see MAV_ROI enum)| MISSION index/ target ID. (see MAV_ROI enum)| ROI index (allows a vehicle to manage multiple ROI's)| Empty| x the location of the fixed ROI (see MAV_FRAME)| y| z|  */
 	VEHICLE_CMD_NAV_PATHPLANNING = 81, /* Control autonomous path planning on the MAV. |0: Disable local obstacle avoidance / local path planning (without resetting map), 1: Enable local path planning, 2: Enable and reset local path planning| 0: Disable full path planning (without resetting map), 1: Enable, 2: Enable and reset map/occupancy grid, 3: Enable and reset planned route, but not occupancy grid| Empty| Yaw angle at goal, in compass degrees, [0..360]| Latitude/X of goal| Longitude/Y of goal| Altitude/Z of goal|  */
-	VEHICLE_CMD_NAV_GUIDED_LIMITS=90, /* set limits for external control |timeout - maximum time (in seconds) that external controller will be allowed to control vehicle. 0 means no timeout| absolute altitude min (in meters, WGS84) - if vehicle moves below this alt, the command will be aborted and the mission will continue.  0 means no lower altitude limit| absolute altitude max (in meters)- if vehicle moves above this alt, the command will be aborted and the mission will continue.  0 means no upper altitude limit| horizontal move limit (in meters, WGS84) - if vehicle moves more than this distance from it's location at the moment the command was executed, the command will be aborted and the mission will continue. 0 means no horizontal altitude limit| Empty| Empty| Empty|  */
+	VEHICLE_CMD_NAV_GUIDED_LIMITS=90, /* set limits for external control |timeout - maximum time (in seconds) that external controller will be allowed to control vehicle. 0 means no timeout| absolute altitude min (in meters, AMSL) - if vehicle moves below this alt, the command will be aborted and the mission will continue.  0 means no lower altitude limit| absolute altitude max (in meters)- if vehicle moves above this alt, the command will be aborted and the mission will continue.  0 means no upper altitude limit| horizontal move limit (in meters, AMSL) - if vehicle moves more than this distance from it's location at the moment the command was executed, the command will be aborted and the mission will continue. 0 means no horizontal altitude limit| Empty| Empty| Empty|  */
 	VEHICLE_CMD_NAV_GUIDED_MASTER=91, /* set id of master controller |System ID| Component ID| Empty| Empty| Empty| Empty| Empty|  */
 	VEHICLE_CMD_NAV_GUIDED_ENABLE=92, /* hand control over to an external controller |On / Off (> 0.5f on)| Empty| Empty| Empty| Empty| Empty| Empty|  */
 	VEHICLE_CMD_NAV_LAST = 95, /* NOP - This command is only used to mark the upper limit of the NAV/ACTION commands in the enumeration |Empty| Empty| Empty| Empty| Empty| Empty| Empty|  */

src/modules/uORB/topics/vehicle_gps_position.h

@@ -79,7 +79,7 @@ struct vehicle_gps_position_s {
 	bool vel_ned_valid;				/**< Flag to indicate if NED speed is valid */
 
 	uint64_t timestamp_time;			/**< Timestamp for time information */
-	uint64_t time_gps_usec;				/**< Timestamp (microseconds in GPS format), this is the timestamp which comes from the gps module   */
+	uint64_t time_gps_usec;				/**< Timestamp (microseconds in GPS format), this is the timestamp which comes from the gps module. It might be unavailable right after cold start, indicated by a value of 0 */
 
 	uint8_t satellites_used;			/**< Number of satellites used */
 };