diff --git a/libraries/AP_Compass/Compass_learn.cpp b/libraries/AP_Compass/Compass_learn.cpp
index abf067bb21..f1492d8794 100644
--- a/libraries/AP_Compass/Compass_learn.cpp
+++ b/libraries/AP_Compass/Compass_learn.cpp
@@ -37,16 +37,8 @@ void CompassLearn::update(void)
             return;
         }
 
-        // setup the expected earth field at this location
-        float declination_deg=0, inclination_deg=0, intensity_gauss=0;
-        AP_Declination::get_mag_field_ef(loc.lat*1.0e-7, loc.lng*1.0e-7, intensity_gauss, declination_deg, inclination_deg);
-
-        // create earth field
-        mag_ef = Vector3f(intensity_gauss*1000, 0.0, 0.0);
-        Matrix3f R;
-
-        R.from_euler(0.0f, -ToRad(inclination_deg), ToRad(declination_deg));
-        mag_ef = R * mag_ef;
+        // setup the expected earth field in mGauss at this location
+        mag_ef = AP_Declination::get_earth_field_ga(loc) * 1000;
 
         sem = hal.util->new_semaphore();
 
@@ -68,8 +60,9 @@ void CompassLearn::update(void)
         }
 
         // set initial error to field intensity
+        float intensity = mag_ef.length();
         for (uint16_t i=0; i<num_sectors; i++) {
-            errors[i] = intensity_gauss*1000;
+            errors[i] = intensity;
         }
         
         hal.scheduler->register_io_process(FUNCTOR_BIND_MEMBER(&CompassLearn::io_timer, void));