Finding elongation of expandable distal end of catheter

A system comprising:

• a shaft extending along a longitudinal axis including a distal end;
• an expandable assembly coupled to the distal end of the shaft, the expandable assembly comprising:
• a position signal transmitter;
• and
• a position signal receiver;
• one or more processors configured to receive signals from the position signal transmitter and the position signal receiver;
• and
• a non-transitory computer readable medium comprising instructions that, when executed by one or more processors, are configured to cause the system to:
• estimate, based at least in part on signals received from the position signal transmitter of the expandable assembly, a position and longitudinal direction of the position signal transmitter, the expandable assembly disposed along the longitudinal axis;
• estimate, based at least in part on signals received from the position signal receiver disposed on the expandable assembly, a position of the position signal receiver;
• project an estimated position of the position signal receiver on an axis defined by the estimated longitudinal direction of the position signal transmitter;
• and
• correct the estimated position of the position signal receiver by projecting the estimated position of the position signal receiver on the axis defined by the estimated longitudinal direction of the position signal transmitter.