diff --git a/libraries/AP_Math/location.cpp b/libraries/AP_Math/location.cpp
index eaac6d6114..6ee488d3d5 100644
--- a/libraries/AP_Math/location.cpp
+++ b/libraries/AP_Math/location.cpp
@@ -24,9 +24,6 @@
 #include <stdlib.h>
 #include "AP_Math.h"
 
-// radius of earth in meters
-#define RADIUS_OF_EARTH 6378100
-
 // scaling factor from 1e-7 degrees to meters at equater
 // == 1.0e-7 * DEG_TO_RAD * RADIUS_OF_EARTH
 #define LOCATION_SCALING_FACTOR 0.011131884502145034f