1. An image guided surgery system comprising a surgical instrument, a tracking system for locating and tracking an object in a surgical environment, the tracking system including a tracking sensor system, in particular a tracking camera system; and a medical navigation system processing tracking data from the tracking system and image data of the object, and outputting image data and navigational assistance on a display; characterized in that the instrument, the tracking system including the sensor system and the medical navigation system including the display are integrated in one single portable unit.