A system for accounting for electromagnetic, EM, distortion with an EM tracking system, comprising: a database storing distortion fingerprints that characterize distortion morphologies associated with each of one or more known EM distorters, the distorters being tools, devices or combinations thereof that cause distortions to an EM field; a sensor array configured to sense EM energy in a target volume and collect it as data; and an EM sensing correction module configured to: analyze the data from the sensor array to detect EM distorters in the target volume, wherein the EM sensing correction module is configured to compare distortion fingerprints stored in the database with the data from the sensor array to identify and locate a known EM distorter or a combination of known EM distorters causing distortion in an EM field in the target volume, characterised in that the EM sensing correction module is further configured to: determine an error contribution to an overall error of the EM field introduced by the detected distorter by comparing a baseline error map representing a baseline error in a clean environment having no distortions with an overall error measured using the data from the sensor array, and compensate for the error contribution and/or generate an error map intra-operatively showing the error contribution of the distorter and visualizing regions of low and high error measurements in the target volume by combining the baseline error map of the clean environment with the distortion morphology associated with the identified and located distorter. a database storing distortion fingerprints that characterize distortion morphologies associated with each of one or more known EM distorters, the distorters being tools, devices or combinations thereof that cause distortions to an EM field; a sensor array configured to sense EM energy in a target volume and collect it as data; and an EM sensing correction module configured to: analyze the data from the sensor array to detect EM distorters in the target volume, wherein the EM sensing correction module is configured to compare distortion fingerprints stored in the database with the data from the sensor array to identify and locate a known EM distorter or a combination of known EM distorters causing distortion in an EM field in the target volume, characterised in that the EM sensing correction module is further configured to: determine an error contribution to an overall error of the EM field introduced by the detected distorter by comparing a baseline error map representing a baseline error in a clean environment having no distortions with an overall error measured using the data from the sensor array, and compensate for the error contribution and/or generate an error map intra-operatively showing the error contribution of the distorter and visualizing regions of low and high error measurements in the target volume by combining the baseline error map of the clean environment with the distortion morphology associated with the identified and located distorter. compensate for the error contribution and/or generate an error map intra-operatively showing the error contribution of the distorter and visualizing regions of low and high error measurements in the target volume by combining the baseline error map of the clean environment with the distortion morphology associated with the identified and located distorter. <EOS>