AP_Camera: added CAM_TRIGG_DIST parameter

for triggering every N meters of GPS distance travelled

libraries/AP_Camera/AP_Camera.cpp

@@ -41,6 +41,13 @@ const AP_Param::GroupInfo AP_Camera::var_info[] PROGMEM = {
     // @User: Standard
     AP_GROUPINFO("SERVO_OFF",   3, AP_Camera, _servo_off_pwm, AP_CAMERA_SERVO_OFF_PWM),
 
+    // @Param: TRIGG_DIST
+    // @DisplayName: Camera trigger distance
+    // @Description: Distance in meters between camera triggers. If this value is non-zero then the camera will trigger whenever the GPS position changes by this number of meters regardless of what mode the APM is in
+    // @User: Standard
+    // @Range: 0 1000
+    AP_GROUPINFO("TRIGG_DIST",  4, AP_Camera, _trigg_dist, 0),
+
     AP_GROUPEND
 };
 
@@ -209,3 +216,24 @@ AP_Camera::control_msg(mavlink_message_t* msg)
 }
 
 
+// update location, for triggering by GPS distance moved
+void AP_Camera::update_location(const struct Location &loc)
+{
+    if (_trigg_dist == 0.0f) {
+        return;
+    }
+    if (_last_location.lat == 0 && _last_location.lng == 0) {
+        _last_location = loc;
+        return;
+    }
+    if (_last_location.lat == loc.lat && _last_location.lng == loc.lng) {
+        // we haven't moved - this can happen as update_location() may
+        // be called without a new GPS fix
+        return;
+    }
+    if (get_distance(&loc, &_last_location) < _trigg_dist) {
+        return;
+    }
+    _last_location = loc;
+    trigger_pic();
+}

libraries/AP_Camera/AP_Camera.h

@@ -54,6 +54,8 @@ public:
     void            configure_msg(mavlink_message_t* msg);
     void            control_msg(mavlink_message_t* msg);
 
+    void update_location(const struct Location &loc);
+
     static const struct AP_Param::GroupInfo        var_info[];
 
 private:
@@ -70,6 +72,9 @@ private:
     void            throttle_pic();     // pictures blurry? use this trigger. Turns off the throttle until for # of cycles of medium loop then takes the picture and re-enables the throttle.
     void            distance_pic();     // pictures blurry? use this trigger. Turns off the throttle until closer to waypoint then takes the picture and re-enables the throttle.
     void            transistor_pic();   // hacked the circuit to run a transistor? use this trigger to send output.
+    
+    AP_Float        _trigg_dist;     // distance between trigger points (meters)
+    struct Location _last_location;
 
 };