BIM level 2: what will it mean for you?

Source: RTM Dec/Jan 17

Alan Barrow, managing director of ABA Surveying Ltd, discusses the importance of BIM and the significant interest in the recently launched BIM4Rail.

BIM Level 2, meaning collaborative working with the project data being freely available to all parties through the implementation of a common data environment, is now a mandatory requirement for all government construction projects. 

Network Rail has recognised the benefits of this approach and on 7 December 2016 BIM4Rail was launched to more than 120 delegates working in the rail sector. Forty delegates were anticipated and 120 turned up! Such is the interest in BIM4Rail. 

The term BIM, originally coined in the USA, was derived from a ‘Building Information Model’ and was focused on a building’s life cycle, its design and construction, its operation and maintenance. 

The benefits and efficiencies of a BIM type model in the construction sector were immediately recognised by the UK government. The original American model was taken apart, analysed and an anglicised version fit for the UK is the result. From its original focus on buildings, the concept has been expanded significantly and now covers assets of every description. The rail sector itself includes buildings, structures, stations and a quite unique infrastructure, and resulting from this the need to establish an even more focused BIM was recognised with the formation of BIM4Rail. 

It is therefore fitting and more relevant to our rail sector that, at its launch, BIM4Rail redefined BIM as ‘Better Information Management’. 

Ever since the railways began, the industry has included specialisms which we now call disciplines such as gauging, signalling, permanent way, switches and crossovers, overhead line equipment, power supply, structures – the list is endless and forever expanding. 

Every one of these disciplines has developed over time its own method of recording and maintaining its assets. These records started as paper-based hardcopy records with procedures that dictated the frequency of inspection, the measurements to be recorded, the condition to be noted and any action recommended. These records have, until the advent of the computer, been paper-based and could only be viewed at the point of storage. 

It is true that some of the recording has now migrated to the logbook or spreadsheet on computers, and some of the condition reporting has now migrated to an image with the advent of the digital camera or smartphone. While the ability to share data has been improved, the accessibility is still predominantly at the local level or the point of storage, and the data does not exist in anything like a common data environment (CDE) that would facilitate sharing or interoperability.  

The probability also is that for many disciplines all this recordkeeping is referenced to a schematic drawing or a plan of dubious scale, accuracy, content and currency and much of it, when in schedule or tabulated form, is bespoke to the discipline itself and not readily sharable with other disciplines. 

Aibot X6 3 edit

Complete electronic format 

BIM Level 2 requires that all project and asset information, documentation and data is in electronic format. Geometrical data must be in 3D and both 3D geometrical and non-graphical data must be kept in a CDE and available to all parties. 

As a project manager, have you ever asked one of your contractors or installers for an as-built survey of their finished work and did they answer “There was no need for an as-built survey because we built it according to the design”?  – Yeah right. 

In the BIM world, your as-built data may well be the basis of design for other disciplines in the same way as your design could equally have been based on the as-built data of others. Concerned? You should be. 

Scale, accuracy, content and currency are all fundamental to the effectiveness of the BIM if all disciplines are going to share their data with confidence. If the BIM data is found to be inaccurate, incomplete or out of date then that BIM implementation will have failed and the whole BIM concept falls into disrepute. 

Will you be responsible for that or will you de-risk it? 

In the BIM Level 2 world the experienced surveyor has the pivotal role to play in keeping the BIM accurate, complete and current. Existing and emerging technologies, if used by professionals, have made and will continue to make the collection of survey data a highly efficient and automated process and largely error-free. 

Control networks, GNSS (global navigation satellite system) and total stations properly employed will ensure location information is maintained accurately to just a few millimetres. 

Tripod-mounted 3D scanners will record all site details, either as progress or after completion, at the touch of a button and are not selective – everything gets recorded. Just register the point cloud to grid and save it in the database. That way, if any designer needs current information at any time the most recent point cloud can be interrogated. No need to develop the full as-built CAD model until the end of the project. 

Unmanned aerial systems (UAVs) have made a seismic shift in topographical surveying of open territory, but due to limitations of accuracy and operation (only operation with line of sight currently being permitted) their application in the rail sector is at the moment largely limited to inspection work on structures and buildings. This may well change in the future. 

Train-mounted 3D scanning systems like the RILA have been approved by Network Rail for GRIP 1-3 stages and are already being used for long route surveys and electrification schemes.  

More and more we shall see ‘all in one’ permanent way surveying equipment like the Leica SiTrack. This is being tested by ABA for Network Rail approval at all GRIP stages. The SiTrack is a second generation track measuring device that is able to locate itself using on-board systems that include GNSS, INS (inertial navigation system) and a non-contact optical laser odometer (DMU). 

These systems will measure and electronically record track cant and gauge better than 1mm, track and S&C rail head profiles better than 0.3mm while simultaneously recording a point cloud of track, trackside detail and OLE at 1 million points per second, and all at survey grade accuracy at a comfortable walking speed of 3km per hour. 

BIM Level 2 mandates 3D modelling and location accuracy is the key to confidence in every BIM implementation. No matter how impressive the modelling, if it is in the wrong place it is useless.

That is why the software behind systems like the SiTrack will combine input from all the sensors, GNSS, INS, DMU together with any available ground control information, firstly to validate that they are mutually supportive, and then to derive the statistically most correct trajectory and hence the highest location accuracy possible. 

Currently surveyors use software that will interrogate the recorded data and automatically extract information such as rail alignments, cant, gauge, rail geometry, OLE wire runs with H&S, clearance with .sc0 files and rail head profiles with more functionality being developed all the time. 

The next step will be to extend this software functionality to analyse the recorded data for changes over time and thereby facilitate and enable the asset maintenance routine in becoming proactive rather than reactive. 

Can you see where this is leading? With proper direction and commonality of procedures and interoperability being driven by the BIM4Rail initiative, there is no reason at all why the many project-based BIMs should not mature into a national database accessible to all for better planning and maintenance of rail assets. 

The BIM Level 2 concept is to create a project database for the life of the project and not just for the immediate task in hand. ‘Data - fit for purpose’ needs to be re-written to be ‘Data - fit for any purpose’ – just think about the other disciplines that will use it. 

Quality surveying and modelling is the foundation on which confidence in the BIM will be built. Be prepared to invest in this quality and consider any cost implication as de-risking the future. All parties in the supply chain will be able to share precise data avoiding duplication, reducing the risk of errors and minimising waste and cost. An investment in quality surveying is an investment for the future that will repay itself many times over.



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