In an example, a graphical user interface can be used to display a graphical representation of a virtual reference structure for an anatomic structure, the reference structure being determined from geometry of the anatomic structure. A location parameter along the reference structure is determined in response to a first user input from a user input device. A graphical proxy marker is displayed on the graphical representation of the reference structure based on the location parameter. A fixed location is selected along the reference structure for a final graphical marker in response to a second user input from the from the user input device. An output visualization is generated to include at least one view of the anatomic structure and a graphical representation of the final graphical marker at the fixed location.
