AP_GPS: Improve comments and documentation (NFC)

libraries/AP_GPS/AP_GPS.h

@@ -134,9 +134,9 @@ public:
         uint16_t vdop;                      ///< vertical dilution of precision in cm
         uint8_t num_sats;                   ///< Number of visible satellites
         Vector3f velocity;                  ///< 3D velocity in m/s, in NED format
-        float speed_accuracy;               ///< 3D velocity accuracy estimate in m/s
-        float horizontal_accuracy;          ///< horizontal accuracy estimate in m
-        float vertical_accuracy;            ///< vertical accuracy estimate in m
+        float speed_accuracy;               ///< 3D velocity RMS accuracy estimate in m/s
+        float horizontal_accuracy;          ///< horizontal RMS accuracy estimate in m
+        float vertical_accuracy;            ///< vertical RMS accuracy estimate in m
         bool have_vertical_velocity:1;      ///< does GPS give vertical velocity? Set to true only once available.
         bool have_speed_accuracy:1;         ///< does GPS give speed accuracy? Set to true only once available.
         bool have_horizontal_accuracy:1;    ///< does GPS give horizontal position accuracy? Set to true only once available.
@@ -297,7 +297,7 @@ public:
         return last_message_time_ms(primary_instance);
     }
 
-	// return true if the GPS supports vertical velocity values
+    // return true if the GPS supports vertical velocity values
     bool have_vertical_velocity(uint8_t instance) const {
         return state[instance].have_vertical_velocity;
     }
@@ -398,7 +398,7 @@ protected:
 
 private:
     // returns the desired gps update rate in milliseconds
-    // this does not provide any gurantee that the GPS is updating at the requested
+    // this does not provide any guarantee that the GPS is updating at the requested
     // rate it is simply a helper for use in the backends for determining what rate
     // they should be configuring the GPS to run at
     uint16_t get_rate_ms(uint8_t instance) const;
@@ -407,7 +407,7 @@ private:
         // the time we got our last fix in system milliseconds
         uint32_t last_fix_time_ms;
 
-        // the time we got our last fix in system milliseconds
+        // the time we got our last message in system milliseconds
         uint32_t last_message_time_ms;
     };
     // Note allowance for an additional instance to contain blended data

libraries/AP_GPS/AP_GPS_ERB.h

@@ -46,42 +46,42 @@ private:
         uint16_t length;
     };
     struct PACKED erb_ver {
-        uint32_t time;
+        uint32_t time;      ///< GPS time of week of the navigation epoch [ms]
         uint8_t ver_high;
         uint8_t ver_medium;
         uint8_t ver_low;
     };
     struct PACKED erb_pos {
-        uint32_t time;
+        uint32_t time;      ///< GPS time of week of the navigation epoch [ms]
         double longitude;
         double latitude;
-        double altitude_ellipsoid;
-        double altitude_msl;
-        uint32_t horizontal_accuracy;
-        uint32_t vertical_accuracy;
+        double altitude_ellipsoid;    ///< Height above ellipsoid [m]
+        double altitude_msl;          ///< Height above mean sea level [m]
+        uint32_t horizontal_accuracy; ///< Horizontal accuracy estimate [mm]
+        uint32_t vertical_accuracy;   ///< Vertical accuracy estimate [mm]
     };
     struct PACKED erb_stat {
-        uint32_t time;
+        uint32_t time;      ///< GPS time of week of the navigation epoch [ms]
         uint16_t week;
-        uint8_t fix_type;
+        uint8_t fix_type;   ///< see erb_fix_type enum
         uint8_t fix_status;
         uint8_t satellites;
     };
     struct PACKED erb_dops {
-        uint32_t time;
-        uint16_t gDOP;
-        uint16_t pDOP;
-        uint16_t vDOP;
-        uint16_t hDOP;
+        uint32_t time;      ///< GPS time of week of the navigation epoch [ms]
+        uint16_t gDOP;      ///< Geometric DOP
+        uint16_t pDOP;      ///< Position DOP
+        uint16_t vDOP;      ///< Vertical DOP
+        uint16_t hDOP;      ///< Horizontal DOP
     };
     struct PACKED erb_vel {
-        uint32_t time;
-        int32_t vel_north;
-        int32_t vel_east;
-        int32_t vel_down;
-        uint32_t speed_2d;
-        int32_t heading_2d;
-        uint32_t speed_accuracy;
+        uint32_t time;      ///< GPS time of week of the navigation epoch [ms]
+        int32_t vel_north;  ///< North velocity component [cm/s]
+        int32_t vel_east;   ///< East velocity component [cm/s]
+        int32_t vel_down;   ///< Down velocity component [cm/s]
+        uint32_t speed_2d;  ///< Ground speed (2-D) [cm/s]
+        int32_t heading_2d; ///< Heading of motion 2-D [1e5 deg]
+        uint32_t speed_accuracy; ///< Speed accuracy Estimate [cm/s]
     };
 
     // Receive buffer

libraries/AP_GPS/AP_GPS_NOVA.h

@@ -114,26 +114,26 @@ private:
 
     struct PACKED bestpos
     {
-        uint32_t solstat;
-        uint32_t postype;
-        double lat;
-        double lng;
-        double hgt;
-        float undulation;
-        uint32_t datumid;
-        float latsdev;
-        float lngsdev;
-        float hgtsdev;
+        uint32_t solstat;      ///< Solution status
+        uint32_t postype;      ///< Position type
+        double lat;            ///< latitude (deg)
+        double lng;            ///< longitude (deg)
+        double hgt;            ///< height above mean sea level (m)
+        float undulation;      ///< relationship between the geoid and the ellipsoid (m)
+        uint32_t datumid;      ///< datum id number
+        float latsdev;         ///< latitude standard deviation (m)
+        float lngsdev;         ///< longitude standard deviation (m)
+        float hgtsdev;         ///< height standard deviation (m)
         // 4 bytes
-        uint8_t stnid[4];
-        float diffage;
-        float sol_age;
-        uint8_t svstracked;
-        uint8_t svsused;
-        uint8_t svsl1;
-        uint8_t svsmultfreq;
-        uint8_t resv;
-        uint8_t extsolstat;
+        uint8_t stnid[4];      ///< base station id
+        float diffage;         ///< differential position age (sec)
+        float sol_age;         ///< solution age (sec)
+        uint8_t svstracked;    ///< number of satellites tracked
+        uint8_t svsused;       ///< number of satellites used in solution
+        uint8_t svsl1;         ///< number of GPS plus GLONASS L1 satellites used in solution
+        uint8_t svsmultfreq;   ///< number of GPS plus GLONASS L2 satellites used in solution
+        uint8_t resv;          ///< reserved
+        uint8_t extsolstat;    ///< extended solution status - OEMV and greater only
         uint8_t galbeisigmask;
         uint8_t gpsglosigmask;
     };

libraries/AP_GPS/AP_GPS_SBP2.cpp

@@ -309,7 +309,7 @@ AP_GPS_SBP2::_attempt_state_update()
         state.vertical_accuracy     = (float) last_pos_llh.v_accuracy * 1.0e-3f;
 
         //
-        // Set flags appropriartely
+        // Set flags appropriately
         //
         state.have_vertical_velocity   = true;
         state.have_speed_accuracy      = !is_zero(state.speed_accuracy);