diff --git a/APMrover2/GCS_Mavlink.pde b/APMrover2/GCS_Mavlink.pde
index 7375cddfdf..a4aa65e151 100644
--- a/APMrover2/GCS_Mavlink.pde
+++ b/APMrover2/GCS_Mavlink.pde
@@ -1,5 +1,8 @@
 // -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 
+// default sensors are present and healthy: gyro, accelerometer, rate_control, attitude_stabilization, yaw_position, altitude control, x/y position control, motor_control
+#define MAVLINK_SENSOR_PRESENT_DEFAULT (MAV_SYS_STATUS_SENSOR_3D_GYRO | MAV_SYS_STATUS_SENSOR_3D_ACCEL | MAV_SYS_STATUS_SENSOR_ANGULAR_RATE_CONTROL | MAV_SYS_STATUS_SENSOR_ATTITUDE_STABILIZATION | MAV_SYS_STATUS_SENSOR_YAW_POSITION | MAV_SYS_STATUS_SENSOR_XY_POSITION_CONTROL | MAV_SYS_STATUS_SENSOR_MOTOR_OUTPUTS)
+
 // use this to prevent recursion during sensor init
 static bool in_mavlink_delay;
 
@@ -104,34 +107,23 @@ static NOINLINE void send_attitude(mavlink_channel_t chan)
 
 static NOINLINE void send_extended_status1(mavlink_channel_t chan, uint16_t packet_drops)
 {
-    uint32_t control_sensors_present = 0;
+    uint32_t control_sensors_present;
     uint32_t control_sensors_enabled;
     uint32_t control_sensors_health;
 
+    // default sensors present
+    control_sensors_present = MAVLINK_SENSOR_PRESENT_DEFAULT;
+
     // first what sensors/controllers we have
-    control_sensors_present |= (1<<0); // 3D gyro present
-    control_sensors_present |= (1<<1); // 3D accelerometer present
     if (g.compass_enabled) {
-        control_sensors_present |= (1<<2); // compass present
+        control_sensors_present |= MAV_SYS_STATUS_SENSOR_3D_MAG; // compass present
     }
-    control_sensors_present |= (1<<3); // absolute pressure sensor present
-    if (g_gps != NULL && g_gps->status() >= GPS::NO_FIX) {
-        control_sensors_present |= (1<<5); // GPS present
+    if (g_gps != NULL && g_gps->status() > GPS::NO_GPS) {
+        control_sensors_present |= MAV_SYS_STATUS_SENSOR_GPS;
     }
-    control_sensors_present |= (1<<10); // 3D angular rate control
-    control_sensors_present |= (1<<11); // attitude stabilisation
-    control_sensors_present |= (1<<12); // yaw position
-    control_sensors_present |= (1<<13); // altitude control
-    control_sensors_present |= (1<<14); // X/Y position control
-    control_sensors_present |= (1<<15); // motor control
 
-    // now what sensors/controllers are enabled
-
-    // first the sensors
-    control_sensors_enabled = control_sensors_present & 0x1FF;
-
-    // now the controllers
-    control_sensors_enabled = control_sensors_present & 0x1FF;
+    // all present sensors enabled by default except rate control, attitude stabilization, yaw, altitude, position control and motor output which we will set individually
+    control_sensors_enabled = control_sensors_present & (~MAV_SYS_STATUS_SENSOR_ANGULAR_RATE_CONTROL & ~MAV_SYS_STATUS_SENSOR_ATTITUDE_STABILIZATION & ~MAV_SYS_STATUS_SENSOR_YAW_POSITION & ~MAV_SYS_STATUS_SENSOR_XY_POSITION_CONTROL & ~MAV_SYS_STATUS_SENSOR_MOTOR_OUTPUTS);
 
     switch (control_mode) {
     case MANUAL:
@@ -140,33 +132,31 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan, uint16_t pack
 
     case LEARNING:
     case STEERING:
-        control_sensors_enabled |= (1<<10); // 3D angular rate control
-        control_sensors_enabled |= (1<<11); // attitude stabilisation
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_ANGULAR_RATE_CONTROL; // 3D angular rate control
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_ATTITUDE_STABILIZATION; // attitude stabilisation
         break;
 
     case AUTO:
     case RTL:
     case GUIDED:
-        control_sensors_enabled |= (1<<10); // 3D angular rate control
-        control_sensors_enabled |= (1<<11); // attitude stabilisation
-        control_sensors_enabled |= (1<<12); // yaw position
-        control_sensors_enabled |= (1<<13); // altitude control
-        control_sensors_enabled |= (1<<14); // X/Y position control
-        control_sensors_enabled |= (1<<15); // motor control
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_ANGULAR_RATE_CONTROL; // 3D angular rate control
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_ATTITUDE_STABILIZATION; // attitude stabilisation
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_YAW_POSITION; // yaw position
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_XY_POSITION_CONTROL; // X/Y position control
+        control_sensors_enabled |= MAV_SYS_STATUS_SENSOR_MOTOR_OUTPUTS; // motor control
         break;
 
     case INITIALISING:
         break;
     }
 
-    // at the moment all sensors/controllers are assumed healthy
-    control_sensors_health = control_sensors_present;
-
-    if (!compass.healthy) {
-        control_sensors_health &= ~(1<<2); // compass
+    // default to all healthy except compass and gps which we set individually
+    control_sensors_health = control_sensors_present & (~MAV_SYS_STATUS_SENSOR_3D_MAG & ~MAV_SYS_STATUS_SENSOR_GPS);
+    if (g.compass_enabled && compass.healthy && ahrs.use_compass()) {
+        control_sensors_health |= MAV_SYS_STATUS_SENSOR_3D_MAG;
     }
-    if (!compass.use_for_yaw()) {
-        control_sensors_enabled &= ~(1<<2); // compass
+    if (g_gps != NULL && g_gps->status() > GPS::NO_GPS) {
+        control_sensors_health |= MAV_SYS_STATUS_SENSOR_GPS;
     }
 
     int16_t battery_current = -1;