Capturing Chinese high-speed rails

Author: Jing-long Xie

High-speed rail (HSR) in China has witnessed significant development in recent years. With nearly two-thirds of the world's HSR, exceeding 25,000 kilometres in 2017, China now has the world's largest HSR network. The world’s longest and most extensively used HSR network relies on leading surveying technology to keep China on the move.

Surveying rail is indispensable for rail design, construction and maintenance. China Railway Design Corporation (CRDC), a large-scale survey and design consultant enterprise, has surveyed and designed more than 40,000 km of rail, including 7,500 km of HSR. Surveying and mapping this large extension of rail brings challenges to surveyors and engineers. To overcome them, CRDC experts rely on the Leica Pegasus:Backpack wearable mobile mapping system to capture railways.

Surveying in Shenyang, China

The unique wearable reality capture sensor platform has revolutionised the traditional survey methods of CRDC. With the Pegasus:Backpack’s two LiDAR scanners and five high dynamic cameras, the team is improving efficiency by generating an accurate, fully-registered and colourised 3D point cloud model of the rail environment, even in GNSS-denied areas thanks to the Simultaneous Localisation and Mapping (SLAM) positioning technology integrated in the reality capture platform.

The operator collecting the data turned on the Pegasus:Backpack and connected it to tablet to see in real time the data acquisition, images, LiDAR units and GNSS signal strength. With no need of using targets, CRDC surveyors walked and biked along the Shenyang rail collecting dense 3D point cloud and crisp images without worrying about GNSS coverage. One person carrying the ergonomic and ultralight Pegasus:Backpack completed the survey planned route in one hour collecting data from inside of the rail tunnels and outdoors.

“The Pegasus:Backpack is a very powerful measuring tool. I believe this will promote the reform of new measurement methods in the near future,” said Chun-xi Xie, rail survey department manager at CRDC.

Beyond hardware

Efficient technology that increases productivity goes beyond hardware or sensor integration. Of equal importance is the related software workflow and processing speed. CDRC surveyors could visualise in real time the data captured to decide if additional information layers were needed before leaving the site.

Once all data was collected, the team of experts imported the georeferenced 3D point clouds with panoramic images to Leica Pegasus:MapFactory to extract coordinates and features for a wide range of rail applications including:

• Produce topography models and plans of the area
• Draw 2D plan of a railway viaduct in AutoCAD
• Measure height and size of the high-voltage power towers near the railways
• Measure the width and features of the culvert
• Extract coordinates of railway power poles
• Create as-built models of the railways.

The core business of CRDC covers planning, survey and design, engineering consultation, and project management of rail. The workflow provided by Pegasus:Backpack solution fully meets CRDC’s  accuracy and efficiency requirements for preliminary railway surveys, saving time, cutting expenses, and increasing four times the efficiency in comparison with the traditional survey methods.