diff --git a/libraries/AP_Math/definitions.h b/libraries/AP_Math/definitions.h
index 3194dc607d..88199349d5 100644
--- a/libraries/AP_Math/definitions.h
+++ b/libraries/AP_Math/definitions.h
@@ -110,6 +110,7 @@ static const double WGS84_E = (sqrt(2 * WGS84_F - WGS84_F * WGS84_F));
 // speed and distance conversions
 #define KNOTS_TO_METERS_PER_SECOND 0.51444
 #define FEET_TO_METERS 0.3048
+#define METRES_TO_FEET 3.280839895013123
 
 // Convert amps milliseconds to milliamp hours
 // Amp.millisec to milliAmp.hour = 1/1E3(ms->s) * 1/3600(s->hr) * 1000(A->mA)