Abstract: A digital angle gauge includes a housing body. The housing body includes a first surface having a first light opening, a second surface, opposing the first surface, having a second light opening, and a third surface, adjacent the first surface and the second surface, having a third light opening. The digital angle gauge includes an orientation sensor configured to measure an orientation of the housing body with respect to gravity. The digital angle gauge includes a light source, wherein the light source emits light based on the measured orientation of the housing body. The digital angle gauge includes a light guide, disposed in the housing body, directing the light from light source to the first light opening, the second light opening, and the third light opening.

Abstract: An apparatus is disclosed for use with a surgical navigation system. The apparatus comprises a tool body and tool attachment onto which emitters are fixedly mounted. At least one tool tip is removably coupled with the tool body. An electrical sensor is positioned to be operated when the tool tip is changed either by coupling the tip to or removing the tip from the tool body. A controller responsive to the operation of switch detects when the tip has been changed. An alarm responsive to the controller indicates that the tool tip has been removed or changed so that the tip can be recalibrated relative to a known position in the surgical navigation system.