Abstract: Triangle orientation discrimination threshold (TOD) criteria are determined utilizing the field experimental data. The discrimination probability of the tank and triangle pattern in various ranges is given by the statistical method, respectively using the forced-choice experimental method based on their field measured image. Further, the Weibull function is fitted to the discrimination probability data by the least-square deviation method, and the TOD criteria corresponding to 75% correct discrimination probability are determined. A comparison with John’s criteria and TOD criteria provided by TNO shows that this method can determine a reasonable evaluation value for the TOD criteria.

Key words: triangle orientation discrimination threshold, field performance, Weibull function, discrimination probability