An impact motion tracking system for tracking an object in a three-dimensional space, whereby: - a motion tracking sensor comprises a housing, a magnetic measurement module (32, 32') and an inertial measurement module; - a transmitter module generates magnetic fields; - said magnetic measurement module (32, 32') measures magnetic fields generated by said transmitter module, said magnetic measurement modules (32, 32') has a fixed positional relationship with at least one object portion of said object (10, 20); - said inertial measurement module measures at least one of a linear acceleration and an angular acceleration, said inertial measurement module has a fixed positional relationship with said at least one object portion (10, 20); - an electronic processor receives measured signals from said motion tracking sensor; - said electronic processor derives an impact motion information for said object portion (10, 20) based on received measured signals from said inertial measurement module; - said electronic processor derives a magnetic motion information for said object portion (10, 20) based on received measured signals from said magnetic measurement module; - said electronic processor periodically calibrates impact motion information with magnetic motion information; characterized in that - said object being at least one of a crash test dummy and a vehicle to be crashed; - one magnetic measurement module serves as reference magnetic measurement module for said object portion (10, 20); and said electronic processor periodically calibrates magnetic motion information from other magnetic measurement modules with referential magnetic motion information from said reference magnetic measurement module. - a motion tracking sensor comprises a housing, a magnetic measurement module (32, 32') and an inertial measurement module; - a transmitter module generates magnetic fields; - said magnetic measurement module (32, 32') measures magnetic fields generated by said transmitter module, said magnetic measurement modules (32, 32') has a fixed positional relationship with at least one object portion of said object (10, 20); - said inertial measurement module measures at least one of a linear acceleration and an angular acceleration, said inertial measurement module has a fixed positional relationship with said at least one object portion (10, 20); - an electronic processor receives measured signals from said motion tracking sensor; - said electronic processor derives an impact motion information for said object portion (10, 20) based on received measured signals from said inertial measurement module; - said electronic processor derives a magnetic motion information for said object portion (10, 20) based on received measured signals from said magnetic measurement module; - said electronic processor periodically calibrates impact motion information with magnetic motion information; characterized in that - said object being at least one of a crash test dummy and a vehicle to be crashed; - one magnetic measurement module serves as reference magnetic measurement module for said object portion (10, 20); and said electronic processor periodically calibrates magnetic motion information from other magnetic measurement modules with referential magnetic motion information from said reference magnetic measurement module.