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A methodology for developing helmet-mounted display (HMD) symbology from conception to flight is being developed within the Defence Evaluation and Research Agency (DERA). As part of this development, experiments have been undertaken to evaluate target locator cues (TLCs). A TLC is designed to represent the direction and angular distance from the pilot's line-of-sight outside the HMD FOV. A previous study by Geiselman and Tsou identified three potentially effective TLCs which were used in these experiments. The first experiment was conducted on the DERA fused imagery simulation testbed (FIST). FIST is a simulation facility which projects images on a large curved screen to simulate HMD and HUD symbology. A 10 degree simulated FOV was used for the HMD symbology. The results showed two of the TLCs to be significantly better than the third. The experiment was repeated using the Viper II helmet used. The result were very similar to those obtained in the first experiment, helping to validate the use of low fidelity simulation in symbology development.

This paper describes an experiment conducted to investigate the type of display symbology that most effectively conveys height information to users of head-down plan-view radar displays. The experiment also investigated the use of multiple information sources (redundancy) in the design of such displays. Subjects were presented with eight different height display formats. These formats were constructed from a control, and/or one, two, or three sources of redundant information. The three formats were letter coding, analogue scaling, and toggling (spatially switching the position of the height information from above to below the aircraft symbol). Subjects were required to indicate altitude awareness via a four-key, forced-choice keyboard response. Error scores and response times were taken as performance measures. There were three main findings. First, there was a significant performance advantage when the altitude information was presented above and below the symbol to aid the representation of height information. Second, the analogue scale, a line whose length indicated altitude, proved significantly detrimental to performance. Finally, no relationship was found between the number of redundant information sources employed and performance. The implications for future aircraft and displays are discussed in relation to current aircraft tactical displays and in the context of perceptual psychological theory.