Control device, endoscope system, and position detection method

A control device comprising:

• a connection interface;
• and
• processing circuitry configured to:
• select candidate coordinates of a target element, wherein the target element is one of a magnetic field generation element or a magnetic field detection element;
• calculate a candidate vector based on coordinates of a reference element, the candidate coordinates, and a detection signal received via the connection interface from the magnetic field detection element in response to detection of a magnetic field generated by the magnetic field generation element, wherein the reference element is the other of the magnetic field generation element or the magnetic field detection element;
• calculate a vector norm error based on the candidate vector;
• update maximum likelihood coordinates to the candidate coordinates when the vector norm error is smaller than a minimum value of one or more previously-calculated vector norm errors;
• determine whether the vector norm error is within a first range;
• and
• select new candidate coordinates when the vector norm error is not within the first range.