Visual Search for MILSTD 2525 Glyphs

Glyphs are representations of multivariate data used for quickly discriminating information. They can represent values on more than one data dimension via physical attributes such as shape, size, and color (Ward, 2002). The United States military uses a set of glyph symbology (MILSTD 2525) to represent soldiers, equipment and personnel on the battlefield. In this study the authors selected a subset of features from these glyphs to i) evaluate their search efficiency, ii) determine whether differences in efficiency exist between levels of the same feature, and iii) identify the overall difficulty of search. The study compared 4 features: the length and orientation of a line, a central symbol and a text identifier. These represented air speed and direction, aircraft type and a unique aircraft identifier, respectively. Two variations of each feature were used to evaluate search efficiency across different levels of a given feature. Participants identified which side of the screen contained an oddball glyph, or if they saw no oddball. Set sizes 6, 12, and 18 were tested, with target absent trials occurring 10% of the time. Distractors were a set of homogenous glyphs from which the target stimuli only differed by a change in one of the tested features. Response time and accuracy were the major dependent variables, with search slopes being calculated for analysis. Results indicate that participants were not able to distinguish changes in text identifiers, with poor accuracy and relatively slow search efficiencies. Performance for most of the other features was excellent. Participants were slower at identifying a low level of air speed and directional change versus higher levels. This finding is consistent with other work in search asymmetries and indicates that interpretation of these glyphs may be more difficult for some situations than others.