Abstract：In the special measurement environment, using prism free total station has its unique advantages.However the ranging accuracy under different observation conditions highly influences the observation results.In order to study the influence of different monitoring environment on the ranging accuracy of prism free total station, Topcon ES-602 G total station is taken as an example, A systematic experiment and analysis on its ranging accuracy are carried out. The corresponding experimental scheme is designed from different reflective surface material, i. e., the surface color, the laser beam incident angle and different corners. The corresponding fitting function model is obtained by using regression analysis method and its influence on the precision of ranging is analyzed. The results show that the influence on the ranging accuracy of the largest is marble. Red brick and wood have weak influence on the ranging accuracy. The color of the reflection surface is negatively correlated with the ranging accuracy. The lighter the color is, the stronger the reflection signal and the higher range accuracy. The incident angle of the laser beam is inversely proportional to the ranging accuracy. In order to ensure the accuracy of the measurement, the incident angle should be controlled within 30 degrees. The reflection surface has a linear relations with the ranging accuracy. The larger the corner has higher the accuracy. The smaller the corner and the range error may be greater.

Keyword：total station;prism free;distance measurement precision;