A system comprising: a first catheter (110) configured for insertion into an organ in the body of a patient and comprising one or more measuring electrodes (PME) multiple sets of current injection electrodes (CIE) configured for attachment relative to the body in the body of a patient one electronic control system coupled to multiple electrode assemblies current injection (CIE) and one or more measuring electrodes (PME) and configured to: cause current to flow between said plural sets of electrodes current injection (CIE ) to generate a field in the organ in response to current flow, measuring the field at multiple locations within the organ using the one or more measurement electrodes (PME) in response to current flow, measuring the field in multiple additional electrodes in the body a tracking system configured for positions within the body of said one or more measuring electrodes (PME) a processing system coupled to the electronics and configured to: model the field using field measurements of one or more measurement electrodes (PME) and positions within the body of one or more measurement electrodes expected signals to determine measurements of the field in additional locations within the body using the field model and determining a position of said one or more additional electrodes in the body based on measurements made by the additional electrodes and measures of expected signals certain field.Un sistema que comprende: un primer catéter (110) configurado para su inserción en un órgano en el cuerpo de un paciente y que comprende uno o más electrodos de medición (PME) múltiples conjuntos de electrodos de inyección de corriente (CIE) configurados para su fijación en relación con el órgano en el cuerpo de un paciente un sistema de control electrónico acoplado a los múltiples conjuntos de electrodos de inyección de corriente (CIE) y a uno o más electrodos de medición (PME) y configurado para: hacer que la corriente fluya entre dichos múltiples conjuntos de electrod
