Mobile Laser Scanning Systems for Measuring the Clearance Gauge of Railways: State of Play, Testing and Outlook

Abstract

The paper contains a survey of mobile scanning systems for measuring the railway clearance gauge. The research was completed as part of the project carried out for the PKP (PKP Polish Railway Lines S.A., Warsaw, Poland) in 2011-2013. The authors conducted experiments, including a search for the latest solutions relating to mobile measurement systems that meet the basic requirement. At the very least, these solutions needed to be accurate and have the ability for quick retrieval of data. In the paper, specifications and the characteristics of the component devices of the scanning systems are described. Based on experiments, the authors did some examination of the selected mobile systems to be applied for measuring the clearance gauge. The Riegl (VMX-250) and Z+F (Zoller + Fröhlich) Solution were tested. Additional test measurements were carried out within a 30-kilometer section of the Warsaw-Kraków route. These measurements were designed so as to provide various elements of the railway infrastructure, the track geometry and the installed geodetic control network. This ultimately made it possible to reduce the time for the preparation of geodetic reference measurements for the testing of the accuracy of the selected systems. Reference measurements included the use of the polar method to select profiles perpendicular to the axis of the track. In addition, the coordinates selected were well defined as measuring points of the objects of the infrastructure of the clearance gauge. All of the tested systems meet the accuracy requirements initially established (within the range of 2 cm as required by the PKP). The tested systems have shown their advantages and disadvantages.

Keywords: database; measurement of clearance gauge; mobile laser scanning; photogrammetry.

Figure 1

The coordinate system of the RIEGL VMX-250. Axis X, vehicle travel direction; Y, vertical on top of rails and pointing up; Z, perpendicular to the XY plan in the nadir direction.

Figure 2

Managing cross-sections in the database. The small outlined region (top right) is 20 × 50 mm. This region contains data where the cross clearance data and scanner data overlap, triggering white rectangles that are shown by the system (lower left picture). The operator should check this region to determine the source of the overlap. The operator can retrieve image data (lower right) to check/verify; in this case, the questionable area is the branch.

Figure 3

Determination of the section numbers in the clearance gauge. Dimensions in mm. RIV is code of international trade.

Figure 4

System 1: Z+F Profiler 9000 scanner on a railroad carriage. In the picture, the installation of the Z+F scanner and construction on the platform are shown ((left) rear view; (right) side view).

Figure 5

System 2 based on a solution by RIEGL VMX-250 mounted on the platform.

Figure 6

Cross-section through the railway station at Słomniki, obtained with System 2. We see the point clouds after classification (dark green, lower part; bright green, average height; red, rails; blue, traction pole).

Figure 7

Clearance with measured railway infrastructure elements obtained from rail gauge measurements: (a) in the background, the cloud of points from the Z+F Profiler 9000 system; (b) in the background, the cloud of points originating from the RIEGL VMX-250 system.

Figure 8

Cross-sections with automated railheads done by Terrasolid. (A) Perpendicular to the track; (B) Along the track; extracted automatically.

Figure 9

The animation window in the implemented program.

Figure 10

A 3D view presenting a point cloud.

Figure 11

Image viewer. We see the pictures from cameras installed on the RIEGL system and set up in four directions.

Figure 12

A 2D cross-section: clearance gauge and the point cloud around. Coordinates of the axes are in meters.

Figure 13

Cargo geometry and clearance editor/profiler. Coordinates of the axes are in meters. Figure presents the critical points method which makes it possible to enter the shape of cargo (lower and upper left). On the basis of points that have been entered, cross-sections in the XY (upper right) and YZ (lower right) planes are generated.