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An investigation was made to determine the visual sizes required for the identification of standard and revised Leroy alphanumerics, which were televised at resolutions of 10, 8, and 6 lines per symbol height. The visual size needed for 99-percent identification accuracy was similar for resolutions of 10 and 8 lines, but a significantly larger visual size was required for symbols resolved by 6 lines. There were no significant differences in visual sizes required for identification of standard versus revised Leroy symbols at any value of resolution. The findings were used to calculate the effective area for viewing televised symbols.

The speed and accuracy with which five subjects identified military map symbols were determined with five different resolutions in lines per symbol height on a television monitor in three experiments. The first two experiments indicated that the minimum acceptable resolution is approximately 17 lines even after considerable practice. The third experiment indicated that a slightly lower resolution is permissible only with an optimum contrast of detail and a carefully selected and maintained television system. Recommendations are made for field installations., See also AD639750.