In [1], the authors of this paper presented the state-of-the-art regarding the five-axis measuring systems and simulation methods used for determination of measurement uncertainty. The simulation model for correction and modeling of probe head errors in five-axis measuring systems was proposed. Besides correction, it can be used to simulate probe head errors for any probe orientation which can find such orientation of probes that gives the best accuracy. Such an approach may contribute to manufacturers' costs reduction through minimization of the risk of wrong decisions when stating the workpiece's compliance with its geometrical specifications. Development of this model was a first step towards creation of fully functional virtual model of five-axis CMM. However, few steps more have to be taken before the final implementation of this model. Firstly, the machine kinematics model has to be connected with the model of probe head kinematics, next, the geometric calibration of the thus-constructed five-axis system kinematic chain has to be performed. At the end, the model has to be extended in order to take into account all other possible errors related to the functioning of the probe (for example influences of usage of different stylus lengths and ball diameters, repeatability of head and probe calibration processes, probe head hysteresis), influences of the measured work piece, metrological software being used, and external interfering factors (mainly the influence of ambient conditions).  
A virtual machine for five-axis coordinate system should include three possible modes of operation of such a system: measurement in three-axis mode with fixed probe orientation, measurement done using only rotational movements of head, and measurement involving CMM movement and head rotations. For the first mode, the virtual model of typical three-axis CMM could easily be adapted. In this case, the biggest problem is infinite orientation possibilities for the probe head. It should be considered for how many orientations Probe Errors (PE) should be identified experimentally and how to model the errors for rest of orientations. The basis for second mode modeling is the kinematic model of probe head, however additional issues associated with machine stabilization and CMM holding the same position during measurement need to be analyzed (the recommendations of ISO 9283 standard, which is dedicated to accuracy testing of industrial robots, could be adapted here). Appropriate research could be performed utilizing a laser interferometer or high accuracy laser tracking systems. The most difficult task is measurement in five-axis mode in which the previously mentioned cases have to be considered, but also the subsequent challenges should be formulated, for example the description of the measurement movement as the combination of the translational and rotary motions.  
As was shown in [1], there are almost none publications regarding five-axis measuring systems which use probe heads with continuous articulation. There are some works dealing with five-axis systems but they deal mainly with CNC machining centers [2; 3; 4] or with CMMs with rotary tables [5] and are devoted to modeling of kinematic errors of these systems. This is why this paper is focused mainly on the research undertaken in Laboratory of Coordinate Metrology (LCM) at Cracow University of Technology where the work on virtual models of five-axis measuring systems are in a high stage of development.