diff --git a/APMrover2/APMrover2.pde b/APMrover2/APMrover2.pde
index 8e2fad2e1d..382124c85f 100644
--- a/APMrover2/APMrover2.pde
+++ b/APMrover2/APMrover2.pde
@@ -363,7 +363,6 @@ static int32_t          gps_base_alt;
 ////////////////////////////////////////////////////////////////////////////////
 // Constants
 const	float radius_of_earth 	= 6378100;	// meters
-const	float gravity 			= 9.81;		// meters/ sec^2
 
 
 // true if we have a position estimate from AHRS
diff --git a/APMrover2/GCS_Mavlink.pde b/APMrover2/GCS_Mavlink.pde
index 07814b3864..bd3f2fb96f 100644
--- a/APMrover2/GCS_Mavlink.pde
+++ b/APMrover2/GCS_Mavlink.pde
@@ -355,9 +355,9 @@ static void NOINLINE send_raw_imu1(mavlink_channel_t chan)
     mavlink_msg_raw_imu_send(
         chan,
         micros(),
-        accel.x * 1000.0 / gravity,
-        accel.y * 1000.0 / gravity,
-        accel.z * 1000.0 / gravity,
+        accel.x * 1000.0 / GRAVITY_MSS,
+        accel.y * 1000.0 / GRAVITY_MSS,
+        accel.z * 1000.0 / GRAVITY_MSS,
         gyro.x * 1000.0,
         gyro.y * 1000.0,
         gyro.z * 1000.0,
@@ -1647,9 +1647,9 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
 
             // m/s/s
             Vector3f accels;
-            accels.x = packet.xacc * (gravity/1000.0);
-            accels.y = packet.yacc * (gravity/1000.0);
-            accels.z = packet.zacc * (gravity/1000.0);
+            accels.x = packet.xacc * (GRAVITY_MSS/1000.0);
+            accels.y = packet.yacc * (GRAVITY_MSS/1000.0);
+            accels.z = packet.zacc * (GRAVITY_MSS/1000.0);
             
             ins.set_gyro(gyros);