Network Rail recently commissioned a large-scale project to create a 3D digital model of Liverpool Street Station in London. The model was to be based largely on 3D laser scan data collection in the field by surveying teams, which would then be supplemented and cross-checked against existing asset records.

The logistics of producing such a model relied heavily on integrating data with some 29,000 legacy drawings from the archive in York, some of which dated back to the original construction of the station in the late 1800s.

Relying on these drawings alone would import a large element of risk when producing a current as-built record so, to supplement the model, over 600 fully-coordinated 3D HDS laser scans were produced of the entire station.

Large amounts of data

The surveying teams worked in non-operational hours to minimise any impact on the general public. First, a fully-coordinated survey grid was created and then seven teams could conduct laser scan and reflectorless survey activities.

The post-processing of the data sets produced from the laser scanners is a sizeable task in itself due to the sheer volume of data collected. It was agreed that splitting the clouds was essential in order to reduce the files to a manageable size.

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Using Autodesk Recap, each cloud was converted into an Autodesk Revit 2015 native point cloud file format. It could then be linked into Revit in order to re-construct the station, making the process much more manageable.

Once the sections and plans were determined through the cloud, the modelling process could begin. As each scan has to be registered and cloud- fitted to create a cohesive model, and there were many millions of surveyed points, powerful hardware was required to manage the data sets.

Enriching the data

Whilst the point cloud gives a dimensionally-accurate 3D representation, from a BIM perspective it is still very much dumb data with little embedded information. In the spirit of BIM, and using the point cloud and legacy data as a base, a Revit model was created which contained data-rich components with built-in parameters to enable additional asset data to be introduced. This embedded data can then provide a wealth of information for renovation, construction, facilities management and, indeed, the asset lifecycle of the station itself.

Of course, laser scanners can only capture points which can be seen from the scan position and will not identify what lies beneath the surface. Therefore additional GPR (ground penetrating radar) and MEP (mechanical, electrical and plumbing) surveys were carried out to build a fuller picture of the station and its components.

This project was undertaken by Bridgeway Consulting and utilised expertise from both the BIM and geomatics departments within the organisation. Should Network Rail need to capture more data in the future, Bridgeway can mobilise its in-house ground investigation, site investigation, and infrastructure services teams to carry out intrusive investigations and condition inspections. The additional data gathered from these works can
then be linked, visualised and geo-coordinated to the BIM model, working to the principles of true BIM.

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Bridgeway’s service offering doesn’t end with the handover of the model. Helping clients achieve their goals in information management is one of the core values to its BIM consultancy service. With this in mind, the company is engaging with its clients to help them understand how they can implement a ‘single source of truth’ from their common data environment through the use of BS1192 workflows. Bridgeway is also helping clients to standardise certain approaches regarding the flow of construction data within their projects.

Laser Scan to model of platform areas

A number of BIM workshops were set up in order to develop the model and maintain its manageable status, categorisation and zoning of spaces to aid the structure of information. Data from the model can be delivered in numerous ways and various formats to ensure interoperability.

Working from initial data collection through to data processing, modelling, management and consultancy, Bridgeway is building a platform to manage major projects and the ongoing monitoring and utilisation of intelligent data, bringing key benefits to public and private sector clients.

Written by Simon Hatch, BIM manager at Bridgeway Consulting