Apparatus and method for displaying an operational area

An operational area is displayed to an operative of a host platform, such as a pilot in an aircraft. The operational area is defined within an external real-world environment relative to said host platform. A viewing device, such as a helmet mounted display is configured to provide a three-dimensional view of said external real-world environment, and has a screen, and a processor comprising an input for receiving real-time first data representative of a specified target and its location within the external real-world environment and configured to receive or obtain second data representative of at least one characteristic of the target. The processor also uses the data to calculate a geometric volume representative of a region of influence of the target relative to the real-world external environment and/or said host platform, generate three-dimensional image data representative of said geometric volume, and display a three dimensional model on the screen. The three-dimensional model is projected or blended into the view of the external real-world environment at the relative location therein of the target.