1. A method of determining a position of a probe that has been inserted into a body of a subject, comprising the steps of: providing a processing unit and a probe model; maintaining the probe model with a model of topologies comprising a range of shapes assumable by said probe; determining an apparent conformation of said probe in said body with the processing unit; using the processing unit and the probe model to establish that said apparent conformation is outside said range; using the processing unit to reference said probe model to determine a true conformation of said probe; using the processing unit to adjust said apparent conformation to said true conformation and displaying said true conformation.