The Survey Association (TSA) is the trade body for land, hydrographic and technical surveying companies in the UK. Formed in 1979 to give a focus for private sector businesses, the TSA now has more than 140 member companies all directly involved in the surveying business.
TSA’s role is to promote best practice, to provide a forum for members for discussion, debate and continuing professional development, and to the wider audience, such as engineers, provide guidance on new methods and techniques and a list of suitably qualified and experienced companies.
TSA is also heavily involved in lobbying government and other agencies such as the Environment Agency, regarding policies likely to affect or involve the survey industry.
Many of its members undertake railway surveying and one of these is Severn Partnership, a TSA member since 2002. The company has been involved with the railways for more than 20 years and has witnessed an increasing demand for greater accuracy and repeatability of survey data in 3D coordinates systems, essential with the limited time available during track possessions.
In the ‘British Rail’ days Hallade Survey was the norm measuring versine with ‘spoons and strings’ using levels, cant bars and measuring theodolite straights in a local chained out system which did the job then and at times is still fit for purpose now some Permanent Way Engineers would argue!
However railway survey contracts are now being commissioned over many hundreds of miles on mainline routes such as WCML, ECML, MML, GWR, XRail and more. This is because the 21st century has seen a massive demand for the development of the UK rail infrastructure to help boost the economy, which in part is also due to the increased environmental and political pressure that road and airport expansion has been associated with.
In 2008 The Times reported Network Rail’s chief executive, Ian Coucher’s call for greater engineering efficiency to meet the demands of the 365-day railway. TSA members’ response has combined state of the art surveying technology, bespoke survey methods and phased quality control to deliver night time engineering possession surveys on time and to a consistent high quality.
3D surveys in absolute coordinate systems are combined and backed up with direct gauging measurements for structure clearances such as for platforms, signals, OHLE, tunnels and bridges. Consistency of data is paramount and this is why TSA member companies feed into and follow the Network Rail Survey Standards.
TSA member companies have not only kept up with the latest standards and specifications in the rail industry but also the very latest surveying technology which is constantly evolving.
This has seen the development of track measuring devices (TMD’s) to improve the repeatability of rail measurements for alignment analysis. These are very often operated in absolute 3D coordinate systems using rail grid geodetic software to ensure engineering scale factor 1 over complete ELR’s. These bespoke rail grids provide consistency and allow survey work and design to be carried out across different parts of the network at the same time to meet NR deadlines; they can be used again into the future ‘working from the whole to the part’ underlying a key fundamental survey principle, necessary for quality survey.
The survey monitoring of railway track while under track crossings and nearby construction works such as piling are taking place has traditionally been completed manually. However recent advances in technology have enabled construction and monitoring periods over months to benefit from automated 24 hour monitoring systems with the data automatically emailed off site. A high accuracy TS30 0.5” total station with meteorological readings for automated temperature and pressure adjustments takes observations to prisms fixed to the web of the rail – continually. Reports on vertical rail movement, cant and twist are automatically generated for survey team and client assessment locally and remotely. The Leica Geo-Moss system provides for this and can be even powered by solar panels so it’s environmentally friendly as well as safer than manual on track assessment and also provides cost savings.
Terrestrial laser scanning has enabled the rapid data capture of huge 3D point cloud data sets where access to the rail environment is limited especially with the increased Rail Operator services. Laser scanning has also been developed to affix to the TMD systems and provide even larger data collection through kinematic laser scanning. This type of technology allowed Severn Partnership to survey the Severn Tunnel, 7 km long in three nightshifts, one of which included a walk through with the Amberg GRP5000 kinematic laser scanning system. A rigorous survey spigot control network was installed in the tunnel with GPS control baselines at either end.
Point clouds are an ideal data set for 3D modelling. Many TSA companies have 3D Modelling capability providing the rail industry with fully rendered models for design and visualisations to help throughout all stages of planning particularly useful within GRIP stages 2-6.
The 3D models are used for public consultation meetings, can be published on websites, used for high and low accuracy design, visualisations for signal sighting and interaction outside the rail industry such as at level crossings and railway stations. In the future these 3D models will be increasingly used by the rail industry in the government’s drive to Building Information Model (BIM), which also applies to infrastructure. Advances in BIM in the rail industry will be key to the network’s development and are realised with technical seminars such as that provided by the Permanent Way Institution at the end of February on ‘BIM and S&C’.
Understanding technology is key
Understanding how to use the new technology, software and systems properly with integrated quality control checks is key to maximising value to the railway project. For example S&C surveys need higher accuracies partly due to the trend towards modular renewal. The old S&C is often cut out and replaced in a single possession with no room for dimensional error. All joints and welds are also detailed which requires not only a geomatics surveyor but a railway surveyor to be involved. TSA member companies provide such experience. They also provide track access planning – crucial to maximising possession periods – and an understanding of the role surveyors can provide into the future for the smooth running of the 365- day railway network.
Guidance from the TSA
The association has written and published a series of guidance notes, all of which are downloadable free of charge from its website at: www.tsa-uk.org.uk. Most TSA guidance notes and client guides are additionally endorsed by the RICS and the CICES. The notes cover a wide range of subjects all designed to help clients and members alike to understand and make the most of modern surveying techniques. Subjects covered include accuracies, laser scanning, specifications, building surveys, and working on railways.
In 2008 TSA engaged with other major stakeholders in producing a set of guidelines to de-mystify the use of GPS.
The final results are presented in a set of best practice guides for use both by surveyors and clients. The original study was subsequently updated and launched at the HQ of the Ordnance Survey in April 2012. The document has already been adopted by organisations such as the Environment Agency and Network Rail. Both the 2008 GPS guidance document and the 2012 GNSS document can also be downloaded free of charge from the TSA website.
In 2011 TSA released a new guidance document on Utility Mapping. The document was two years in the making and has been endorsed by a number of major organisations as well as Mark Prisk MP, at that time the Business and Enterprise Minister.
Mr Prisk wrote: ‘I am pleased to see that The Survey Association has produced this document which is not only written in plain and concise English but which will also become a vital source of information for all those concerned with the UK’s construction industry. Clients and contractors alike will find the Utility Guidance note a useful document when commissioning a utility survey and considering health and safety issues.’
A video has been produced to accompany the document and this can be viewed on the TSA’s website.
TSA also liaises with the RICS and CICES on a range of issues and has established a group called the SLG, or Survey Liaison Group. This body meets at regular intervals to examine matters of mutual interest and to ensure that there is little or no duplication of effort by the three bodies.
Rory Stanbridge is secretary general of the TSA (www.tsa-uk.org.uk). Mark Combes is managing director of the Severn Partnership (www.severnpartnership.com)