Symbol discriminability models for improved flight displays

Aviation display system designers and evaluators need to know how discriminable displayed symbols will be over a wide range of conditions to assess the adequacy and effectiveness of flight display systems. If flight display symbols are to be safely recognized by pilots, it is necessary that they can be easily discriminated from each other. Sometimes psychophysical measurements can answer this question, but computational modeling may be required to assess the numerous conditions and even help design the empirical experiments that may be needed. Here we present an image discrimination model that includes position compensation. The model takes as input the luminance values for the pixels of two symbol images, the effective viewing distance, and gives as output the discriminability in just-noticeable-differences (d') and the x and y offset in pixels needed to minimize the discriminability. The model predictions are shown to be a useful upper bound for human symbol identification performance.