diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp b/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp
index 6f8364a696..749aa0e521 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp
@@ -43,19 +43,17 @@ void AP_OpticalFlow::update_position(float roll, float pitch, float sin_yaw, flo
 {
     float diff_roll     = roll  - _last_roll;
     float diff_pitch    = pitch - _last_pitch;
+    float change_x, change_y;   // actual change in x, y coordinates
 
     // only update position if surface quality is good and angle is not
     // over 45 degrees
     if( surface_quality >= 10 && fabsf(roll) <= FORTYFIVE_DEGREES
      && fabsf(pitch) <= FORTYFIVE_DEGREES ) {
-	altitude = max(altitude, 0);
-        // calculate expected x,y diff due to roll and pitch change
-        exp_change_x = diff_roll * radians_to_pixels;
-        exp_change_y = -diff_pitch * radians_to_pixels;
+	    altitude = max(altitude, 0);
 
-        // real estimated raw change from mouse
-        change_x = dx - exp_change_x;
-        change_y = dy - exp_change_y;
+        // change in position is actual change measured by sensor (i.e. dx, dy) minus expected change due to change in roll, pitch
+        change_x = dx - (diff_roll * radians_to_pixels);
+        change_y = dy - (-diff_pitch * radians_to_pixels);
 
         float avg_altitude = (altitude + _last_altitude)*0.5f;
 
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow.h b/libraries/AP_OpticalFlow/AP_OpticalFlow.h
index 53893aeb73..164fddb64b 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow.h
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow.h
@@ -57,17 +57,12 @@ public:
     void    update_position(float roll, float pitch, float sin_yaw, float cos_yaw, float altitude);
 
     // public variables
-    int16_t  raw_dx;            // raw sensor change in x and y position (i.e. unrotated)
-    int16_t  raw_dy;            // raw sensor change in x and y position (i.e. unrotated)
     uint8_t  surface_quality;   // image quality (below 15 you can't trust the dx,dy values returned)
     int16_t  dx,dy;             // rotated change in x and y position
     uint32_t last_update;       // millis() time of last update
     float    field_of_view;     // field of view in Radians
-    float    scaler;            // number returned from sensor when moved one pixel
 
     // public variables for reporting purposes
-    float    exp_change_x, exp_change_y;    // expected change in x, y coordinates
-    float    change_x, change_y;            // actual change in x, y coordinates
     float    x_cm, y_cm;                    // x,y position in cm
 
 protected:
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_ADNS3080.cpp b/libraries/AP_OpticalFlow/AP_OpticalFlow_ADNS3080.cpp
index e4a5951838..87cf0a51ce 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow_ADNS3080.cpp
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_ADNS3080.cpp
@@ -29,7 +29,6 @@ extern const AP_HAL::HAL& hal;
 AP_OpticalFlow_ADNS3080::AP_OpticalFlow_ADNS3080()
 {
     field_of_view = AP_OPTICALFLOW_ADNS3080_08_FOV;
-    scaler = AP_OPTICALFLOW_ADNS3080_SCALER_1600;
 }
 
 // Public Methods //////////////////////////////////////////////////////////////
@@ -176,6 +175,7 @@ void AP_OpticalFlow_ADNS3080::write_register(uint8_t address, uint8_t value)
 void AP_OpticalFlow_ADNS3080::update(void)
 {
     uint8_t motion_reg;
+    int16_t  raw_dx, raw_dy;    // raw sensor change in x and y position (i.e. unrotated)
     surface_quality = read_register(ADNS3080_SQUAL);
     hal.scheduler->delay_microseconds(50);
 
@@ -267,9 +267,9 @@ void AP_OpticalFlow_ADNS3080::update_conversion_factors()
 {
     // multiply this number by altitude and pixel change to get horizontal
     // move (in same units as altitude)
-    conv_factor = ((1.0f / (float)(ADNS3080_PIXELS_X * scaler))
+    conv_factor = ((1.0f / (float)(ADNS3080_PIXELS_X * AP_OPTICALFLOW_ADNS3080_SCALER_1600))
                    * 2.0f * tanf(field_of_view / 2.0f));
     // 0.00615
-    radians_to_pixels = (ADNS3080_PIXELS_X * scaler) / field_of_view;
+    radians_to_pixels = (ADNS3080_PIXELS_X * AP_OPTICALFLOW_ADNS3080_SCALER_1600) / field_of_view;
     // 162.99
 }