We present the results of research of the angle measurement system for direction measurements. Development of the system is based on the dynamic goniometer, whose operation is defined by continuous rotation of the platform with the autocollimating null-indicator. The measurements of angles between mirrors are provided by the null-indicator and optical encoder. The results of the system calibration with the use of standard optical polygon are presented. The computer simulation of the calibration process was carried out, and requirements to optical elements alignment accuracy were estimated.