Methods and systems for outputting depth data during a medical procedure on a patient. Depth data is outputted, representing at least one of relative depth data and general depth data. Tracking information about the position and orientation of a medical instrument and depth information about variations in depth over a site of interest are used. Relative depth data represents the depth information relative to the position and orientation of the instrument. General depth data represents the depth information over the site of interest independently of the position and orientation of the instrument.