+ virtual double position () const { return 0.0; }
+ virtual double width () const { return 0.0; }
+ virtual double elevation () const { return 0.0; }
+
+ virtual PBD::AngularVector signal_position (uint32_t) const { return PBD::AngularVector(); }
+
+ virtual void reset () = 0;
+
+ /* azimut, width or elevation updated -> recalc signal_position -> emit Changed */
+ PBD::Signal0<void> SignalPositionChanged;