diff --git a/ArduCopter/navigation.pde b/ArduCopter/navigation.pde
index ba9e01b84d..59c068d41e 100644
--- a/ArduCopter/navigation.pde
+++ b/ArduCopter/navigation.pde
@@ -304,7 +304,7 @@ static bool waypoint_valid(Location &wp)
 static void
 get_loiter_accel(int16_t accel_req_forward, int16_t accel_req_right)
 {
-    float z_accel_meas = -AP_INTERTIALNAV_GRAVITY * 100;    // gravity in cm/s/s
+    float z_accel_meas = -GRAVITY_MSS * 100;    // gravity in cm/s/s
 
     // update angle targets that will be passed to stabilize controller
     auto_roll = constrain((accel_req_right/(-z_accel_meas))*(18000/M_PI), -4500, 4500);
diff --git a/libraries/AP_InertialNav/AP_InertialNav.cpp b/libraries/AP_InertialNav/AP_InertialNav.cpp
index 741957b2c3..af0f58af1e 100644
--- a/libraries/AP_InertialNav/AP_InertialNav.cpp
+++ b/libraries/AP_InertialNav/AP_InertialNav.cpp
@@ -51,7 +51,7 @@ void AP_InertialNav::update(float dt)
     accel_ef = _ahrs->get_accel_ef();
 
     // remove influence of gravity
-    accel_ef.z += AP_INTERTIALNAV_GRAVITY;
+    accel_ef.z += GRAVITY_MSS;
     accel_ef *= 100;
 
     // remove xy if not enabled
diff --git a/libraries/AP_InertialNav/AP_InertialNav.h b/libraries/AP_InertialNav/AP_InertialNav.h
index 395a6f8143..ad2f06d0dc 100644
--- a/libraries/AP_InertialNav/AP_InertialNav.h
+++ b/libraries/AP_InertialNav/AP_InertialNav.h
@@ -8,7 +8,6 @@
 #include <AP_Baro.h>                    // ArduPilot Mega Barometer Library
 #include <AP_Buffer.h>                  // FIFO buffer library
 
-#define AP_INTERTIALNAV_GRAVITY 9.80665f
 #define AP_INTERTIALNAV_TC_XY   3.0f // default time constant for complementary filter's X & Y axis
 #define AP_INTERTIALNAV_TC_Z    5.0f // default time constant for complementary filter's Z axis
 
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp
index 1d3fd9ba17..1c6d3e6dca 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp
@@ -6,7 +6,7 @@ const extern AP_HAL::HAL& hal;
 
 AP_InertialSensor_Stub::AP_InertialSensor_Stub() {
         Vector3f accels;
-        accels.z = -9.808;
+        accels.z = -GRAVITY_MSS;
         set_accel(accels);
     }