A method for determining a shape of a bendable instrument can include placing the bendable instrument in a neutral position； moving a first control element a first amount until slack is removed from the first control element； moving a second control element a second amount until slack is removed from the second control element； sensing a position of the first control element after moving the first control element the first amount, the sensed position of the first control element being defined as a first control element calibration position； sensing a position of the second control element after moving the second control element the second amount, the sensed position of the second control element being defined as a second control element calibration position. The method can further include bending the instrument by moving one or both of the first control element and the second control element from the respective first control element calibration position and the second control element calibration position； and determining a resulting shape of the bendable instrument based on a distance one or both of the first control element and the second control element respectively moved from the first control element calibration position and second control element calibration.
