diff --git a/libraries/AP_InertialNav/AP_InertialNav.h b/libraries/AP_InertialNav/AP_InertialNav.h
index afcdc62a4f..d34457c41d 100644
--- a/libraries/AP_InertialNav/AP_InertialNav.h
+++ b/libraries/AP_InertialNav/AP_InertialNav.h
@@ -104,6 +104,14 @@ public:
      */
     virtual float       get_altitude() const = 0;
 
+    /**
+     * get_hgt_ctrl_limit - get maximum height to be observed by the control loops in cm and a validity flag
+     * this is used to limit height during optical flow navigation
+     * it will return invalid when no limiting is required
+     * @return
+     */
+    virtual bool       get_hgt_ctrl_limit(float& limit) const = 0;
+
     /**
      * get_velocity_z - returns the current climbrate.
      *