The criterion for wind environment assessment by Wind Engineering Institute Co., Ltd. is based on the relation between the mean wind speeds measured by 3 cup anemometers and the surrounding condition. Recently, ultrasonic anemometers with lower cost and higher performance has become popular and taken place of 3 cup anemometers; 3-cup anemometers respond to the wind speed change slowly for lower wind speeds while they tend to over-rotate for higher wind speeds due to the effect of inertia force. Considering this circumstances, the present paper investigates the difference between 3 cup anemometer and ultrasonic anemometer for the measured values. Based on the results, we propose a correction method for converting the measured values by 3 cup anemometers to those by ultrasonic anemometers.
