Precision Laser Alignment and its Use in the Measurement of the Horizontal Deformation of Large Dams

In this paper,firstly,the authors studied some of the problems concerning laser alignment,which include:the laws of the image formed by round zone plate,atmospheric effect on laser alignment and main points in designing laser source and detector.Secondly,they described the Laser Alignment Instrument developed by the Engineering Surveying Laboratory in our College and its use in the measurement of the horizontal deformation of large dams,The conclusions axe as follows:a) Laser alignment using round zone plate is a better method for alignment survey as compared with other methods.b) Atmospheric effect on the method using round zone plate is smaller than on otherlaser alignment methods,But to obtain an accuracy of 10^-6 on a one-kilometer line,good atmospheric conditions must be chosen.c) In the measurement of the horizontal deformation of large dams,this method proves to be a good one,in which the time for measurement can be shortened,man power reduced and automatic measurement realized with more ease.