A tracking system comprising at least two trackers wherein a first tracker is able to sense positional information of a second tracker in a first reference frame and the second tracker is able to sense positional information of the first tracker in a second reference frame, wherein: the tracking system further comprises a central processor or a distributed setup of processors, positional information of both first and second trackers is configured to be acquired at the same time or with a time difference that is compensated, positional information of both first and second trackers enables calculation of a pose of one tracker with respect to the reference frame of the other tracker , the calculation being over-determined as the positional information of the first tracker in the second reference frame is the inverse of the positional information of the second tracker in the first reference frame, the tracking system further comprising: means for the central processors or the distributed setup of processors to combine the positional information provided to either the central processors or the distributed setup of processors of at least two trackers and to compute a rigid transformation of one reference frame with respect to the other reference frame, wherein the central processor or the distributed setup of processors is configured to estimate the quality of the rigid transformation and/or to reduce measurement noise and/or to improve a quality of the rigid transformation by using the over-determination, each of the trackers comprising: means to send their positional information to either a central processor or to a distributed setup of processors. the tracking system further comprises a central processor or a distributed setup of processors, positional information of both first and second trackers is configured to be acquired at the same time or with a time difference that is compensated, positional information of both first and second trackers enables calculation of a pose of one tracker with respect to the reference frame of the other tracker , the calculation being over-determined as the positional information of the first tracker in the second reference frame is the inverse of the positional information of the second tracker in the first reference frame, the tracking system further comprising: means for the central processors or the distributed setup of processors to combine the positional information provided to either the central processors or the distributed setup of processors of at least two trackers and to compute a rigid transformation of one reference frame with respect to the other reference frame, wherein the central processor or the distributed setup of processors is configured to estimate the quality of the rigid transformation and/or to reduce measurement noise and/or to improve a quality of the rigid transformation by using the over-determination, each of the trackers comprising: means to send their positional information to either a central processor or to a distributed setup of processors. means for the central processors or the distributed setup of processors to combine the positional information provided to either the central processors or the distributed setup of processors of at least two trackers and to compute a rigid transformation of one reference frame with respect to the other reference frame, wherein the central processor or the distributed setup of processors is configured to estimate the quality of the rigid transformation and/or to reduce measurement noise and/or to improve a quality of the rigid transformation by using the over-determination, each of the trackers comprising: means to send their positional information to either a central processor or to a distributed setup of processors. <EOS>