A data processing method of determining the position, in particular location and/or orientation, of a medical device relative to a multitactic detection device for detecting the position of the medical device, the data processing method being executed by a computer and comprising the following steps: a) acquiring medical device position data comprising medical device position information describing a position of the medical device relative to a detection surface in which the detection device is located b) acquiring detection device geometry data comprising detection device geometry information describing a geometry of the detection device c) acquiring detection device geometry uncertainty data comprising detection device geometry uncertainty information describing a detection device geometry uncertainty associated with the geometry of the detection device described by the detection device geometry information, wherein the detection device geometry uncertainty is defined relative to an uncertainty surface d) acquiring surface relative position data comprising surface relative position information describing the relative position between the detection surface and the uncertainty surface e) determining, based on the medical device position data and the detection device geometry data and the detection device geometry uncertainty data and the surface relative position data, medical device position uncertainty data comprising medical device position uncertainty information describing a medical device position uncertainty associated with the position of the medical device, wherein the medical device position uncertainty is defined relative to the uncertainty surface.
