Steerable segmented endoscope and method of insertion

A method for determining the three dimensional shape of an instrument during or after insertion of said instrument into a body cavity, wherein said instrument comprises an elongate body comprising a selectively steerable distal tip, and a plurality of pivotably coupled and automatically controlled segments proximal to said selectively steerable distal tip, wherein adjacent segments of the plurality of segments are pivotable about two intersecting, independent axes, said method comprising:

• advancing said instrument into said body cavity;
• providing axial position data to a controller, wherein said axial position data is relative to a datum;
• providing angular position data to said controller from a respective segment controller associated with each of said plurality of automatically controlled segments, the angular position data comprising relative angular positions of the adjacent segments of the plurality of segments;
• and
• generating in electronic memory of said controller a three-dimensional model of a shape of said instrument using the provided axial position data and the angular position data.