Abstract: Index error of vertical circle and 2C value (two times of collimation axis error) are two important indicators which affect the precision of total station's angle measurement. A South NTS-312L total station with index error of vertical circle overrun and a South NTS-312L total station with 2C overrun are corrected by the calibrator stand with collimators. The experiments show that the index error of vertical circle of the former is reduced from 24" to 6" and 2C of the latter from 19" to -6" respectively after calibrating, the calibrating results according with Verification Regulation of Electronic Tachometer Total Station JJG100-2003. In order to check the calibration results further, both total stations are tested in a field survey, and the results show that the vertical index of the former changes between -3" to 6" range, and 2C value of the latter varies in -6" to 5" range, these numbers basically in agreement with the calibration experiment.

Key words: calibrator stand with collimators, total station, index error of vertical circle, collimation axis error