A surgical navigation system for tracking the position of a work target located inside a patient's body, 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 skin of the patient's body; 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 trackable device further comprises a flexible substrate configured to be secured to the outer surface of the skin of the patient's body, wherein the plurality of tracking points is carried by the flexible substrate. 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 skin of the patient's body; 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 trackable device further comprises a flexible substrate configured to be secured to the outer surface of the skin of the patient's body, wherein the plurality of tracking points is carried by the flexible substrate. 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 trackable device further comprises a flexible substrate configured to be secured to the outer surface of the skin of the patient's body, wherein the plurality of tracking points is carried by the flexible substrate.