A mobile assembly of electrically-powered devices intended to provide a physician with both electromagnetic (EM) and optical tools to track manual surgical instruments and locate target anatomical structures, commonly with respect to pre-acquired images and/or real-time data [e.g., computed tomography (CT), ultrasound (US)] during computer assisted surgery (CAS). It consists of a workstation with controls/display, an EM field generator, a camera, and sensors/spatial markers for attachment to the patient and instruments for position/movement tracking. It is used for multiple procedures (e.g., craniotomy) in various fields [e.g., ear/nose/throat (ENT), craniomaxillofacial (CMF) surgery].