Research on the New Deflection Measurement Method for Large Span Bridges

A new bridge deflection measurement method was proposed,in which the geometric information of co-operant was acquired by using the surveying robot. The angle measurement precision and the distance measurement precision of surveying robot were analysed from two perspectives of systematic error and random error.The measurement error analysis was done by considering the effect of the vertical angle and stadia.Measurement precision of the method was analysed in the least square principle.The analyses have revealed that,when the distance between the instrument and back target is less than 150 m,and the distance between instrument and observational target is less than 200 m,the defection measurement precision excels ±1 mm.The difference of the deflection measurement between the surveying robot and the digital level is less than 0.22 mm,and the relative error is less than 3.3% in a practical sample.The results have shown that the method can meet the precision demand of bridge inspection.