AP_Camera: stop adjusting logged altitudes manually, use location met…

…hods

libraries/AP_Camera/AP_Camera_Logging.cpp

@@ -28,19 +28,22 @@ void AP_Camera_Backend::Write_CameraInfo(enum LogMessages msg, uint64_t timestam
         // completely ignore this failure!  AHRS will provide its best guess.
     }
 
-    int32_t altitude, altitude_rel, altitude_gps;
-    if (current_loc.relative_alt) {
-        altitude = current_loc.alt+ahrs.get_home().alt;
-        altitude_rel = current_loc.alt;
-    } else {
-        altitude = current_loc.alt;
-        altitude_rel = current_loc.alt - ahrs.get_home().alt;
+    int32_t altitude_cm = 0;
+    if (!current_loc.get_alt_cm(Location::AltFrame::ABSOLUTE, altitude_cm)) {
+        // ignore this problem...
     }
+    int32_t altitude_rel_cm = 0;
+    if (!current_loc.get_alt_cm(Location::AltFrame::ABOVE_HOME, altitude_rel_cm)) {
+        // ignore this problem...
+    }
+
+
+    int32_t altitude_gps_cm = 0;
     const AP_GPS &gps = AP::gps();
     if (gps.status() >= AP_GPS::GPS_OK_FIX_3D) {
-        altitude_gps = gps.location().alt;
-    } else {
-        altitude_gps = 0;
+        if (!gps.location().get_alt_cm(Location::AltFrame::ABSOLUTE, altitude_gps_cm)) {
+            // ignore this problem...
+        }
     }
 
     // if timestamp is zero set to current system time
@@ -57,9 +60,9 @@ void AP_Camera_Backend::Write_CameraInfo(enum LogMessages msg, uint64_t timestam
         gps_week    : gps.time_week(),
         latitude    : current_loc.lat,
         longitude   : current_loc.lng,
-        altitude    : altitude,
-        altitude_rel: altitude_rel,
-        altitude_gps: altitude_gps,
+        altitude    : altitude_cm,
+        altitude_rel: altitude_rel_cm,
+        altitude_gps: altitude_gps_cm,
         roll        : (int16_t)ahrs.roll_sensor,
         pitch       : (int16_t)ahrs.pitch_sensor,
         yaw         : (uint16_t)ahrs.yaw_sensor