---

Surveying has great improvements in data collection techniques in last decade.one of these techniques is laser scanner. With that method we can collect 3D data automatically. Investigating of the error sources in TLS measurements is rather complicated due to a large number of influencing factors that are quite interrelated. Thus calibration is an important issue in these devices. Several models have been proposed to improve the accuracy of the laser scanners data until now. Each of these models includes some physically parameters and some empirically parameters which have been produced by observation of residuals diagram, in this paper a parametric model based on the internal structure of laser scanner is presented for calibrating these devices. This model compared with another models shows that due to having just physical parameters and not empirical parameters it can be used for a variety of TLS instruments.