This paper presents the estimation methodology of position of WIP(Work-In-Process). Since the monitoring digital twin synchronizes with a real manufacturing system, it is essential for the CPS (Cyber-Physical System) simulation or on-line simulation. A CPS simulator needs to start a simulation execution for any given time ‘t’, which requires the exact ‘snap-shot’ of the real manufacturing system at time ‘t’. The snapshot is the total state of the manufacturing system including all states of manufacturing facilities as well as all position of WIPs. This paper pro poses the estimation methodology of position of WIPs which can provide the snapshot of a manufacturing system, and the proposed methodology is based on the concept of virtual sen sors. If all WIPs in the system have virtual sensors attached, the movement of the WIP is defined according to other virtual sensor data and the mechanism of the facility. To verify the performance of these estimation methods, positions are compared for the same WIP in simula tion and monitoring
