3D Data Acquisition in Tunnels Optimizing Track Time Using Terrestrial Mobile LiDAR Scanning Michael R. Frecks, PLS President/CEO AREMA 2013 1207
Understanding mobile 3D LiDAR? light detection and ranging Mobile LiDAR sensors are used in situations where large areas need to be mapped with high accuracy. Mobile mapping LiDAR systems contain many of the same components as airborne LiDAR systems, but there are some key differences. These systems are mounted on the back of a vehicle or hy-railer. The laser scanner rotates 360 o continuously during operation, rather than oscillating back and forth. The systems can contain a GPS antenna or two, as well as more than one laser. Components of a Mobile Scanner Basic Principle of Laser Surveying: Basic Principle of Laser Surveying: Object Object Range Accuracy Denver, CO Project: 23.6 miles Scanner location VQ250 Scanner Range 300 m to 80% reflectivity 100 m to 10% reflectivity 1208 AREMA 2013
Accuracy Study Denver Rail 58 control points RMS error in Z 0.02 Average dz -0.005 Minimum dz -0.057 Maximum dz +0.005 Average magnitude 0.008 Root mean square 0.016 Std deviation 0.016 GPS Tunnel Issues the only thing worse than no GPS is intermittent GPS Urban environment similarities Drift IMU carry through Control Track time Look at 4 Data Capture Rail Tunnels Traditional Data Capture boots on the ground Static Data Capture tripod mounted 150 300 Bergen Tunnel, Elizabeth, NJ Mobile Data Capture targets every 500 Mobile Data Capture targets in stations Orange Line Boston, MA Traditional Data Capture Rail One track 5,000 tunnel Reflectorless total station Multiple setups (20) and many 1000 s of shots to collect data Final deliverable cross-sections Very time consuming using valuable track time 5,000 of tunnel requires two days of track time to accomplish data acquisition Three-man crew plus RR flaggers May not get all data required Static Data Capture - Rail Bergen Tunnel, Elizabeth, NJ One track 5,200 tunnel Phase based scanner on rail platform Final deliverable cross-sections Less time consuming using less valuable track time 5,000 of tunnel requires four hours of track time to accomplish data acquisition Five-man crew plus RR flaggers Very rich data set but has radial data 4 tracks and catenary wires 8,800 long tunnel 80 targets RMS error of 0.04 Positive Train Control (PTC) Less time consuming using less valuable track time Targets every 500 requires traverse taking track time 5,000 of tunnel requires 15 minutes of track time to accomplish data acquisition Two-man crew with hy-railer Very rich evenly distributed data point set AREMA 2013 1209
Control point targets are used along the corridor at approximately 500 intervals for QA/QC checks to coordinate datum Control point targets on alternating sides of the corridor/track 2 tracks and catenary wires 3.13 mile long tunnel 20 targets at stations Evaluation of tunnel to above grade features Less time consuming using less valuable track time 4 targets at every station removes the surveyors for the track eliminating track time for the control phase 5,000 of tunnel requires 15 minutes of track time to accomplish data acquisition Two-man crew with hy-railer Very rich evenly distributed data point set Control targets placed at the entrance and exit to the stations and at the beginning of tunnels Control targets placed in a four target configuration (two on each side of tracks) on a vertical plane perpendicular to the tracks with the target face parallel to tracks Control targets white 1 painted square Accuracy MBTA Orange Line Tunnel Adjustments in XYZ MBTA Boston, MA RMS error of 0.04 X Y Z Average Correction 0.093 0.145-0.391 Maximum Correction 2.481 12.527 1.851 1210 AREMA 2013
Safety Out of the Red Zone Collecting rail data in a traditionalal manner can be dangerous fouling track time. Work must be performed during available traffic breaks, which can introduce errors. From a system-wide perspective, clearance information in many cases is incomplete, inaccurate, and difficult to maintain and to access. Summary BENEFITS Safer acquisition Reduced track down time Faster acquisition hours instead of weeks No field revisits through virtual desktop extraction Complete 3d environment Top of rail elevations accurately acquired QUESTIONS? www.terrametrix3d.com AREMA 2013 1211