Error Analysis of Network Sensor Measurement System for Subway Tunnel's Longitudinal Deformation

Using the deformation monitoring system based on digital image sensor,the relative displacement of the object can be gotten directly.Through the transformations of criterion coordinate,the absolute coordinates of the object can be gotten finally.And there are error diffusion and accumulation during transformation.The single scanning's reliable points under error propagation conditions are calculated by establishing a mathematical model,and the method of increasing the reliable points in accordance with the actual situation of Shanghai subway tunnel is proposed.