A method of operating a see-through display, the method comprising: displaying via the see-through display in a first display mode one or more virtual objects with a world-locked position in which a position of each virtual object appears to be fixed relative to real-world objects viewable through the see-through display and the position of each virtual object appears to be moveable relative to a wearer of the see-through display; and determining via an optical sensor and an inertial measurement unit a location and an orientation information of the see-through display in six degrees of freedom; determining via a first tracking filter a first estimate of the orientation and the location of the see-through display in six degrees of freedom; determining via the inertial measurement unit a location and an orientation information of the see-through display in three degrees of freedom; determining via a second tracking filter a second estimate of the orientation and the location of the see-through display in three degrees of freedom; determining via a quality monitor if the first estimate and the second estimate meet a quality metric; wherein a display mode selector is configured to: select the first display mode for operation of the see-through display in which the virtual objects are displayed via the see-through display with the world-locked position if the quality metric is met for the first estimate; otherwise select a second display mode for operation of the see-through display in which the virtual objects are displayed via the see-through display with a body-locked display mode in which the position of each virtual object appears to be fixed relative to the wearer of the see-through display and the position of each virtual object appears to be moveable relative to real-world objects. displaying via the see-through display in a first display mode one or more virtual objects with a world-locked position in which a position of each virtual object appears to be fixed relative to real-world objects viewable through the see-through display and the position of each virtual object appears to be moveable relative to a wearer of the see-through display; and determining via an optical sensor and an inertial measurement unit a location and an orientation information of the see-through display in six degrees of freedom; determining via a first tracking filter a first estimate of the orientation and the location of the see-through display in six degrees of freedom; determining via the inertial measurement unit a location and an orientation information of the see-through display in three degrees of freedom; determining via a second tracking filter a second estimate of the orientation and the location of the see-through display in three degrees of freedom; determining via a quality monitor if the first estimate and the second estimate meet a quality metric; wherein a display mode selector is configured to: select the first display mode for operation of the see-through display in which the virtual objects are displayed via the see-through display with the world-locked position if the quality metric is met for the first estimate; otherwise select a second display mode for operation of the see-through display in which the virtual objects are displayed via the see-through display with a body-locked display mode in which the position of each virtual object appears to be fixed relative to the wearer of the see-through display and the position of each virtual object appears to be moveable relative to real-world objects. select the first display mode for operation of the see-through display in which the virtual objects are displayed via the see-through display with the world-locked position if the quality metric is met for the first estimate; otherwise select a second display mode for operation of the see-through display in which the virtual objects are displayed via the see-through display with a body-locked display mode in which the position of each virtual object appears to be fixed relative to the wearer of the see-through display and the position of each virtual object appears to be moveable relative to real-world objects.