A surgical navigation system for tracking the position of a work target located inside a patient's body in a surgical operating room, wherein the body is compressible and has a distortable outer surface, the navigation system comprising: a trackable device comprising a plurality of tracking points configured to be secured to the outer surface of the skin of the patient's body, wherein the tracking points are configured to be moveable relative to each other when secured to the outer surface of the body, and wherein the trackable device is adapted to be attached to the outer surface of the skin of the patient's body so as to extend around a surgical area on the patient without covering the surgical area; and a computer-implemented tracking system that is adapted to remotely track the positions of each tracking point of the trackable device relative to a coordinate system, the tracking system including a computer processor arrangement adapted to implement a navigation routine that includes the steps: accessing an initial model of the trackable device, the initial model having an initial shape based on initial locations of a set of the tracking points of the trackable device; registering the initial model with an initial position of the work target in an image of the work target; sensing a deformation of the trackable device with the tracking system after registering the initial model; creating a refined model of the trackable device that compensates for the deformation; and calculating the current position of the work target from the refined model, the surgical navigation system characterized in that the navigation routine includes the further steps of: estimating an expected error of the current position of the work target calculated from the initial model and the deformation of the trackable device; and providing an indication to a user when the expected error exceeds a pre-defined maximum error threshold for the work target. a trackable device comprising a plurality of tracking points configured to be secured to the outer surface of the skin of the patient's body, wherein the tracking points are configured to be moveable relative to each other when secured to the outer surface of the body, and wherein the trackable device is adapted to be attached to the outer surface of the skin of the patient's body so as to extend around a surgical area on the patient without covering the surgical area; and a computer-implemented tracking system that is adapted to remotely track the positions of each tracking point of the trackable device relative to a coordinate system, the tracking system including a computer processor arrangement adapted to implement a navigation routine that includes the steps: accessing an initial model of the trackable device, the initial model having an initial shape based on initial locations of a set of the tracking points of the trackable device; registering the initial model with an initial position of the work target in an image of the work target; sensing a deformation of the trackable device with the tracking system after registering the initial model; creating a refined model of the trackable device that compensates for the deformation; and calculating the current position of the work target from the refined model, accessing an initial model of the trackable device, the initial model having an initial shape based on initial locations of a set of the tracking points of the trackable device; registering the initial model with an initial position of the work target in an image of the work target; sensing a deformation of the trackable device with the tracking system after registering the initial model; creating a refined model of the trackable device that compensates for the deformation; and calculating the current position of the work target from the refined model, the surgical navigation system characterized in that the navigation routine includes the further steps of: estimating an expected error of the current position of the work target calculated from the initial model and the deformation of the trackable device; and providing an indication to a user when the expected error exceeds a pre-defined maximum error threshold for the work target. estimating an expected error of the current position of the work target calculated from the initial model and the deformation of the trackable device; and providing an indication to a user when the expected error exceeds a pre-defined maximum error threshold for the work target.