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IDS: capturing reality underground

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IDS: capturing reality underground

Matthias Twardzik and Mark Bell from IDS GeoRadar discuss how they believe the creation of a centralised database for ground penetrating radar (GPR) data, and information from other locating equipment, would result in many clear industry advantages.

The Trenchless Technology industry is consistently finding new solutions to manage the growing complexity of underground assets in dense urban areas. Construction companies, surveyors, councils, utility asset owners and others, need effective and simple solutions to increase the accuracy and productivity of underground mapping through the use of innovative technologies.

In Australia, Dial Before You Dig (DBYD) provides an excellent free service; however, the information is sometimes ‘as planned’ and not ‘as built’, and can be of variable quality and accuracy. In a perfect world, ground penetrating radar (GPR) and other locating equipment could be used to create a highly accurate, centralised database of these assets, consistently updated and regulated by a set of clearly defined standards.

A centralised database has many clear advantages, including more efficient excavation of utilities and the use of less intrusive Trenchless Technologies. Augmented reality could then be used by contractors using tablets with highly accurate in-built GPS indicating exactly where they can and cannot dig, while machine controlled excavation systems could also be set to excavate to these exact limits.

The advancement of GPR has allowed for full 3D capture in systems that can be hand pushed.

The rapid advancement in the development of GPR systems now allows for the full 3D capture of underground assets using arrays of dual polarised GPR antenna, in systems light enough to be hand pushed. This 3D capture capability means that companies involved in large scale construction projects can now be provided with high resolution, clear geo-referenced 3D imagery of subsurface features over large areas while still onsite, allowing them to make preliminary decisions quickly and without significant delay to their operations.

The 3D imagery from these systems makes interpretation of the information easier, thereby minimising the chance for operator error which normally relies on the interpretation of 2D GPR radargrams. The 3D imagery also allows operators to track the exact location, orientation and shape of each pipe in real time rather than requiring to cross each pipe at set locations as is the case with typical 2D GPR systems, which represents significant efficiency and accuracy benefits.

The Stream C is IDS GeoRadar’s answer to ‘reality capture’, or the real-time 3D mapping of underground utilities. Thanks to an array of 34 antennas in dual polarisation spanning less than 1 m in width, and to an innovative algorithm running the One Vision real-time 3D acquisition software, the system can automatically detect pipes and cables.

A pioneering feature within the One Vision software, called automatic pipe detection (APD), gives the operator the ability to easily detect the underground assets, and generate the 3D utility geometry in a much shorter time. In addition, Stream C’s integration with GNSS or Total Station equipment, guarantees that correctly geo-referenced data is obtained in all survey conditions.

The images above show a high-resolution 3D GPR dataset collected with the system at a site in Brisbane. Data collection time for this 30 m x 30 m site was 10 minutes, with an additional 45 minutes spent on data interpretation and pipe picking. With a total time of less than one hour spent on site, the system can utilised to provide a high-resolution image. ABOVE: The plan view of the data and site that the operator views in real time, with utilities clearly identifiable. BELOW: The same plan view with pipes picked automatically and manually on site by the operator.

All utilities and buried objects detected during the acquisition phase can then be automatically transferred to CAD and GIS formats allowing for a complete subsurface GIS based digital map to be produced quickly. Stream C is also aided by ergonomic features, including electronic antenna height adjustment, options to tow manually or operate with a small vehicle and a motor assisted drive wheel.

The system has recently been demonstrated in Australia and New Zealand with positive results and feedback from both countries. Operators have used the system to rapidly cover large areas and provide customers with georeferenced CAD/GIS deliverables, soon after data collection.

The system has also been able to match results provided by utility locating contractors, as well as improve the level of understanding at other sites by providing more complete mapping of complex pipe networks. Results from the system have been identified as providing an important additional tool, to be used alongside traditional utility locating techniques, to improve the level of accuracy and understanding of complex subsurface utility networks.

The Pegasus Stream is vehicle-towed to map road networks.

A strong case can now be made for the collection of laser scan and GPR information in one pass, which would provide more context to the GPR information. Identification of above ground features such as fire hydrants, gas markers and electricity substations can be linked to pipes identified by the GPR and preliminary assumptions about pipe type can be made and verified through potholing.

By combining the aboveground and belowground information into one CAD drawing, the interpreter is able to cross-check pipe positions from the GPR data with the aboveground utility infrastructure mapped with the laser scanner. This collection of in-depth asset information in one pass allows for more accurate building information models (BIM), which can then be used as a shared resource, forming the basis for decisions during a project life-cycle.

IDS GeoRadar currently uses the Pegasus: Stream for utility mapping. The Pegasus: Stream is a vehicle-towed system which combines the Leica Pegasus Two mobile mapping system with the IDS GeoRadar Stream EM’s massive array GPR system, for a complete mapping solution for road networks. It is only a matter of time before smaller, lighter and more economic laser scanners are combined with more compact hand pushed GPR array systems, such as the Stream C, to provide the same day-to-day standard utility mapping and BIM model creation as the Pegasus: Stream.

For more information visit the IDS website.

This article was featured in the March edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet, or mobile device, click here.

If you have news you would like covered in Trenchless Australasia contact Assistant Editor Nick Lovering at nlovering@gs-press.com.au

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