DLR Stratford International Extension
August – October 2010
Greenrail were instructed by Skanska, VolkerRail Joint Venture to provide a full as-built survey and 3D model of the brand new DLR Stratford International Extension. The as-built survey was requested to provided the JV with two main sets of information, firstly, an extremely accurate track survey prior to handing the line back to DLR, and secondly to furnish the design team with a fully profiled 3D model of the entire route to aid with gauging and clearance analysis.
At the start-up meeting on August the 13th 2010 Greenrail presented the joint venture with its pre-planned survey methodology and strategy. This was broken down into three stages to ensure that the +/- 3mm tolerance would be achieved.
Greenrail started the survey by traversing the 5km length of the route. This was undertaken using Leica Geosystems TCPR1201+ total stations with Auto Target Recognition to eliminate any human sighting error. Multiple rounds of angles were taken between every survey control point to strengthen the rigorous network. Following this four day traverse a Leica Geosystems DNA03 digital level was used to hard level all survey control points along the route and then closed back to the start point to calculate any miss-closure.
Our second objective was to measure both North and Southbound roads. Greenrail utilised the Amberg GRP1000 track measuring device positioned by the same total station to ensure continuity between the established traverse and the actual measurement of the rails. The 10km of track survey was measured within tolerance in just 10 working days. This information was handed to the design team to enable them to compare the as-built survey to the original design.
Greenrail Solutions third and final commitment to the JV was to provide the design team with clearance profiles for the entire route. With the sheer amount of profiles required Greenrail chose to carry out this work with the Amberg GRP5000 track measuring device which uses a high definition laser scanner to generate a 3D point cloud. From this point cloud composite profiles can be extracted to show minimum clearances throughout the track corridor.
Below are images extracted from the 3D point cloud. You can see that this information can not only be used to produce the clearance profiles requested, but can be kept by DLR as an asset management tool. Using Amberg Rails free-view software our clients are able to interrogate the point cloud at any given chainage and physically see what assets are there without the need for costly line closures to facilitate track walks.