Terrametrix recently completed 3 miles of tunnel data using the StreetMapper system. After simulating and testing the StreetMapper processing workflow in a real environment for more than a year, Terrametrix took the system to a project containing four tracks and catenary wires in an 8,800-foot-long environment with no GPS for 14 minutes. The final results were an RMS error of 0.04 foot. The project was part of a positive train control (PTC) project and also included a clash detection requirement.

“The tunnel tests have shown that StreetMapper can achieve better than 35 cm positional error in a 2000 m tunnel that takes about 2 minutes to drive,” said Dr. Graham Hunter, the developer of the StreetMapper system. “Most obstructions along a highway due to bridges and buildings will be equivalent to a tunnel less than 500 m; this shows that in these cases a positional error of better than 6m can be expected.” (For more details, see the “Simulated Tunnel Accuracy” Report.)

“Having an accurate system like StreetMapper coupled with the surveying knowledge of how to approach the project in a critical environment like tunnels and streetscapes is a powerful team of expertise,” said Michael Frecks, president and CEO of Terrametrix and a land surveyor for 35 years. Frecks is known for pushing the envelope with scanning applications from static to mobile. “You don’t know what this technology can do until you push it to its limits. The processes created exceptional results on this project.”



Image: Resulting line work and feature extraction from point cloud data.