A location tracking system, comprising: a memory, which is configured to store (i) one or more first impedance-magnitudes, measured at a first electrical frequency between a probe located at a location in an organ of a patient and one or more body-surface electrodes, and (ii) one or more second impedance-magnitudes, measured at a second electrical frequency between the probe located at the location and the one or more body-surface electrodes, wherein the second electrical frequency is different from the first electrical frequency; and a processor configured to: acquire from a calibration tool, prior to inserting the probe, a set of calibration impedance-magnitudes at the first and second electrical frequencies between the calibration tool located at calibration locations and the one or more body-surface electrodes, and acquire corresponding calibration locations; estimate, based on the acquired calibration impedance-magnitudes, one or more calibration zero-frequency impedance-magnitudes between the calibration tool and the one or more body-surface electrodes; estimate, based on the first and second impedance-magnitudes, one or more probe zero-frequency impedance-magnitudes between the probe and the one or more body-surface electrodes; and estimate the location of the probe in the organ by comparing the one or more probe zero-frequency impedance-magnitudes to the calibration zero-frequency impedance-magnitudes. a memory, which is configured to store (i) one or more first impedance-magnitudes, measured at a first electrical frequency between a probe located at a location in an organ of a patient and one or more body-surface electrodes, and (ii) one or more second impedance-magnitudes, measured at a second electrical frequency between the probe located at the location and the one or more body-surface electrodes, wherein the second electrical frequency is different from the first electrical frequency; and a processor configured to: acquire from a calibration tool, prior to inserting the probe, a set of calibration impedance-magnitudes at the first and acquire from a calibration tool, prior to inserting the probe, a set of calibration impedance-magnitudes at the first and second electrical frequencies between the calibration tool located at calibration locations and the one or more body-surface electrodes, and acquire corresponding calibration locations; estimate, based on the acquired calibration impedance-magnitudes, one or more calibration zero-frequency impedance-magnitudes between the calibration tool and the one or more body-surface electrodes; estimate, based on the first and second impedance-magnitudes, one or more probe zero-frequency impedance-magnitudes between the probe and the one or more body-surface electrodes; and estimate the location of the probe in the organ by comparing the one or more probe zero-frequency impedance-magnitudes to the calibration zero-frequency impedance-magnitudes. estimate, based on the acquired calibration impedance-magnitudes, one or more calibration zero-frequency impedance-magnitudes between the calibration tool and the one or more body-surface electrodes; estimate, based on the first and second impedance-magnitudes, one or more probe zero-frequency impedance-magnitudes between the probe and the one or more body-surface electrodes; and estimate the location of the probe in the organ by comparing the one or more probe zero-frequency impedance-magnitudes to the calibration zero-frequency impedance-magnitudes.