A system for precision guidance of surgical procedures on a patient in order to position an object precisely relative to a movable patient. The system comprising a measurement means for measuring the position and orientation of a relevant part of a patient whereto a first object such as an implant or surgical instrument is to be brought into an intended, pre-defined spatial relation, projection means providing a life-size virtual but observable 3D image of said first object, means for determining the relationship between the coordinate system of the measurement means and the coordinate system of the projection means, thereby enabling the virtual but observable 3D image of said first object to be projected in such a way as to represent the intended position and orientation of the first object relative to the relevant part of the patient.
