Abstract:《Specification for the first and second order leveling》 stipulates that the field of rivercrossing GPS leveling has to be flat.An experiment on both embankments of Chaobai River,where elevation difference of observing sites is less than 1 meter,was finished for verifying retionality of the specification.The result shows that the same embankment with height anomaly change rate (α)meets requirements.Two sides of the river with the height anomaly change rate of (α)is beyond the limit of the provisions,and elevation difference between calculated and actual measurement is 26.98 mm.So,first order rivercrossing leveling must abide the specification.