A crossed monitoring device for a head-up display that can be used for displaying a representation of at least one first datum. The device includes a mechanism generating at least one first image from the at least one first datum, a mechanism receiving from the at least one second display at least one second image generated from at least one second datum, and a mechanism selecting one of the first and at least one second image. The device can further include a mechanism modifying images according to characteristics of the displays. Each display can modify the images to be displayed according to its characteristics, and each display can modify the images according to the characteristics of each display.