In general, in one aspect, a method is disclosed for determining information about a position of an object. The method includes: (i) causing current to flow between each of three or more sets of current-injecting electrodes on a first catheter inserted into an organ in a patients body, the organ having a periphery (ii) in response to current flow caused by each set of current injecting electrodes, measuring an electrical signal at each of one or more measuring electrodes located on one or more additional catheters inserted into the organ in the patients body and (iii) determining the position of each of one or more of the measuring electrodes on the additional catheters relative to the first catheter based on the measured signals from the one or more measuring electrodes.
