Laser Scanning in a Railway Environment
We have been carrying out Railway Surveys for the last 15 years predominantly utilising static laser scanning allied to traditional surveying techniques to capture the topography and features within the rail corridor as this provides the 5mm accuracy required for detailed design. The individual scans are registered together to produce an overall pointcloud of the required area.
The resulting point cloud represents the entire scanned volume and this data is used to generate 3D models and 2D data including alignment strings and CleaRoute data. This data can be transferred into AutoCAD and Microstation as well as specific applications for Pway, OLE, Civil and Structural design.
All our site staff are PTS trained and we are “Sentinel” registered and "RISQS - Railway Industry Supplier Qualification Scheme"’ approved. We have the ability to mobilise our workforce at short notice and we are used to working at night within possessions where time is at a premium - an important consideration. Our surveyors also have experience of working on London Underground (LUL), Docklands Light Rail (DLR) and the Liverpool Underground Network.
The Inside Running Edge
One of the first actions after our company formation fourteen years, ago was to engage with Pway engineers to determine how to measure or capture the virtual inside running edge of the rails using laser scanning. Thanks to that engagement and our background in engineering we have developed a technique for capturing the inside running edge of the rail using laser scanning and we have demonstrated the accuracy of this technique in several trials for leading consultancies. To date we believe that we are still the only company able to demonstrate this capability.
Since the introduction of the Network Rail Specification we have had to carry out alignment surveys in line with their specification using the rail shoe but this has also been useful in providing on-going proof of our ability to accurately capture the rail alignment using laser scanning as we overlay the rail shoe alignment onto the registered pointcloud as a secondary check on the registration.
Safety on the Railway as in any other environment is of paramount importance and we have never had any accidents or incidents since the company was founded in 2002. Laser Scanning surveys can contribute to a safer working environment in many cases as :
- We can work in Site Warden Protection Zone –Often the work can be carried out from the cess and red zone working is not required
- Eye-safe lasers to class 1 utilised
- Always more than 2.75m from OLE
- Surveys are completed more quickly resulting in a shorter time on site
- We can carry out the scanning from a rail trolley limiting the carrying of heavy equipment
Railway Survey Accuracy
Engineers normally require a minimum of 5mm accuracy for design on most of the railway infrastructure. By utilising laser scanning linked to control points coordinated by Total Stations we can guarantee the required accuracy. Additionally laser scanning can:
- Pick up the inside running edge of rail to ±5mm
- Pick up structures and features up to 50m distance with ±5mm accuracy
Structure Gauging and CleaRoute Analysis
We have over the last 14 years surveyed hundreds of tunnels and bridges on the rail infrastructure using laser scanning. Early in 2004 we carried out a series of trials with a major consultant and witnessed by Network Rail to prove our capability to accurately gauge structures. In fact the resulting report compared our measurements favourably against traditional laser sweep equipment and highlighted the following advantages :
- Bridges can often be gauged from the cess without the need to access the track
- Point spacing is generally every 2-5mm and hence is virtually guaranteed to pick up any problem areas such as bulges and deformations
- Faster than Laser Sweep
- Repeatable in exactly the same location unlike laser sweep
- Sections can be cut/generated at any spacing
- The scanners will operate in most weather conditions (fog and snow are a problem) but standing water on the rails can also cause a problem
- We can operate in the dark only needing sufficient light (torches) to operate the scanner
- As the scanner picks up all of the visible infrastructure, there is no need for re-visits to capture “missed” data
- We have three scanners which means we can minimise the possession times when they are required - such as in tunnels
Railway Surveys Deliverables
- 3D models or 2D drawings in many formats including AutoCAD, Microstation, Solidworks, Revit etc
- Topographic 2D and 3D drawings
- Cross-sections through tunnels, platforms, overbridges etc for gauging purposes. The data is supplied in SCO format for electronic input into CleaRoute.
- CleaRoute analysis and reporting
- Registered pointcloud of the whole volume of the site. Can be used to identify bulges in tunnels, areas of specific interest & highlight proposed changes.
- Tunnel deformation monitoring data
- Rail alignment data for input into MX
- Signal sighting data from the drivers eye-view
- Height and stagger data
- We have also developed Tunnel Mapping Drawings from the scan data to assist in the inspection of tunnels. By utilising these in the office the engineers can identify areas of concern and target these during the possession thus reducing the time on site and allowing more efficient use of their time in the office. Please contact us for further details.
Depending on the scope and deliverables the cost is is usually cheaper compared with traditional methods of surveying/gauging. When working in normal daylight hours in a Site Warden Protection zone the time taken to carry out the survey and produce the deliverables is significantly less than “normal possession working”.
When considering the cost, time and the other advantages, Scantech’s laser scanning service offers significant benefits compared to traditional surveying
Typical Railway Surveys We Undertake
OLE and Signals
- As Built Structures
- Height and Stagger measurements
- Cross sections
- Gauging and Clearance analysis (CleaRoute)
- Tunnel maps for condition reports
- Topographical surveys
- 3D Models
- Cross Sections
- Gauging and clearance analysis (CleaRoute)
- 3D structural details
- Platform gauging
- Canopy Gauging
- 3D Models
- Measured Building Surveys
- Heritage Surveys to English Heritage Requirements
- BIM Surveys
- 3D Structural models
- Movement monitoring
- Defect Identification
- Permanent way
- S/C surveys