A between groups experiment was carried out to compare navigational strategies in a real environment and in a photorealistic computer graphics simulation of that environment. In this paper, a study that compares a real-world task situation to its computer graphics simulation counterpart is presented. The computer graphics simulation is based on photometry data acquired in the real-world space and is displayed mainly on Head Mounted Displays utilising either monocular or stereo imagery and interaction interfaces such as either the common mouse or head tracking. 105 participants across five conditions were exposed to the real and computer graphics environment and completed a spatial memory task. Participants across conditions were monitored (using software or hardware according to condition) in terms of their navigation patterns and idle time while horizontally rotating around their viewpoint, placed in the centre of the experimental room. An overall main effect was revealed. Relevant statistical analysis showed that the amount of idle time for the participants in the HMD stereo head tracked condition was significantly higher than those in the real-world (p<0.01) condition.