A method for an X-ray-based calibration and adjustment of axis systems by means of an X-ray system comprising a radiation source and a radiation detector , comprising: establishing a kinematic model of the X-ray system with all the kinematic relations for a first position (51t1) on the movement trajectory and describing the same using a first set of kinematic parameters and using parameters to be calibrated, wherein the first set of kinematic parameters and the parameters to be calibrated define a first equation of a system of equations; setting the starting values for the parameters to be calibrated; and calibrating comprising: establishing an X-ray projection of a calibration body for the first position (51t1) on the movement trajectory in order to acquire a first measuring result for at least one feature of the calibration body ; and comparing the first measuring result to a respective reference in order to determine an error measure; and solving the system of equations in order to determine the parameters to be calibrated; wherein the X-ray system comprises at least one robot or multi-element robot ; wherein the robot or multi-element robot moves the radiation source , an object or the detector such that the radiation source , the object and/or the radiation detector are movable in dependence on machine parameters for driving the robot; and wherein the kinematic parameters of the set of kinematic parameters describe the kinematic model of the entire system comprising at least the robot or multi-element robot , wherein the kinematic parameters comprise non-variable kinematic parameters comprising a leg length of a component of the robot or multi-element robot , and variable kinematic parameters comprising the machine parameters which describe the movement or position of the respective joint of the robot or multi-element robot . establishing a kinematic model of the X-ray system with all the kinematic relations for a first position (51t1) on the movement trajectory and describing the same using a first set of kinematic parameters and using parameters to be calibrated, wherein the first set of kinematic parameters and the parameters to be calibrated define a first equation of a system of equations; setting the starting values for the parameters to be calibrated; and calibrating comprising: establishing an X-ray projection of a calibration body for the first position (51t1) on the movement trajectory in order to acquire a first measuring result for at least one feature of the calibration body ; and comparing the first measuring result to a respective reference in order to determine an error measure; and solving the system of equations in order to determine the parameters to be calibrated; establishing an X-ray projection of a calibration body for the first position (51t1) on the movement trajectory in order to acquire a first measuring result for at least one feature of the calibration body ; and comparing the first measuring result to a respective reference in order to determine an error measure; and solving the system of equations in order to determine the parameters to be calibrated; wherein the X-ray system comprises at least one robot or multi-element robot ; wherein the robot or multi-element robot moves the radiation source , an object or the detector such that the radiation source , the object and/or the radiation detector are movable in dependence on machine parameters for driving the robot; and wherein the kinematic parameters of the set of kinematic parameters describe the kinematic model of the entire system comprising at least the robot or multi-element robot , wherein the kinematic parameters comprise non-variable kinematic parameters comprising a leg length of a component of the robot or multi-element robot , and variable kinematic parameters comprising the machine parameters which describe the movement or position of the respective joint of the robot or multi-element robot . <EOS>