| As an important national infrastructure,railway plays an important role in promoting the development of national economy and society.With the increasing mileage of railway operations,the safety and comfort of train operation has also been paid more and more attention,which puts forward higher requirements for the future daily state detection and maintenance technology of existing lines.The railway railway has the characteristics of maintenance and operation synchronization.Only the omni-directional,three-dimensional,high precision and high efficiency surveying and mapping means can meet the maintenance requirements of the existing railway.The three-dimensional laser scanning technology has many advantages,such as comprehensive information acquisition,high measurement accuracy and high collection efficiency,which provides a good foundation for its application in the field of existing railway survey and meets the development needs of existing railway detection technology.At present,experts at home and abroad have carried out the research in this area,however,the whole system is limited by the shortcomings of point cloud collection method and data post-processing algorithm,the relevant application research is not deep enough.In this paper,the terrestrial 3D laser scanning is applied to the field of existing railway survey,the intelligent processing method of existing railway point cloud data is studied,and the feature information extraction of point,line and section in railway engineering is realized.The following four aspects are mainly completed:(1)According to the requirements of the existing railway measurement accuracy,the ranging accuracy of Z+F IMAGER 5010 C terrestrial 3D laser scanner with different scanning resolution is preliminarily studied.Then through the field measurement test of the railway,the reference operation mode is provided for the data acquisition scheme of 3D laser scanning system in the survey of the existing railway,Namely,the survey stations were set along the railway center(or a ‘Z’ route between the shoulders),the scanning work were done under superhigh resolution mode with the distance between stations less than 25 m,sphere targets were used to obtain high quality point cloud data.(2)Based on the measured point cloud data of Dunge Railway and the spatial distribution characteristics of the existing railway,this paper studies the extraction algorithm of the point cloud on the rail top.In this algorithm,firstly,the contact line above the track is extracted through the combination of PCA and mobile laser point clustering to segment the railway buffer zone.Then,in the buffer zone,a variety of constraints such as rail elevation,reflection intensity,track corresponding scale are introduced to extract the point cloud data of the rail top.(3)Based on the continuous change point cloud data of the rail top points of the left and right tracks,according to the equal interval sampling method,combined with the regular characteristics of the changes of track characteristics(curvature,superelevation,positive vector,slope,etc.),the orthogonal least square model is used for fitting.After several iterations,the parameters of plane straight line and circular curve of the left and right tracks are obtained respectively.According to the linear geometric correspondence between the left and right tracks and the railway center line,the actual plane line parameters of the railway center line are obtained,and then the position information of the main point of the railway is extracted.(4)The railway gauge detection method based on the point cloud data of a specific section is studied,and the gauge detection problem is converted into judging the positional relationship between points and polygons on the plane.A railway limit detection model based on the top surface of the rail was constructed.The improved ray algorithm was used to complete the automatic detection of gauge,and the corresponding verification analysis was carried out by using the measured point cloud data of a certain tunnel line. |
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