Mobile rail transit three-dimensional data acquisition method and system

The invention discloses a mobile rail transit three-dimensional data acquisition method and system. The method comprises the following steps: acquiring point cloud data obtained by scanning a rail transit line through a mobile rail scanning car; determining conversion parameters between different coordinate systems through the posture and position relation between a scanner and a trolley on a mobile track scanning vehicle and the posture and position relation between the trolley and a track, and converting the point cloud data into a track coordinate system by using the conversion parameters; and extracting a section position and a corresponding section point cloud from the point cloud data according to the section mileage data, and comparing the section point cloud with the design file data. Rail transit three-dimensional data acquisition is carried out based on the vehicle-mounted mobile laser scanning technology, traditional frame station type scanning is replaced, multiple detection work can be completed