Underground Infrastructure Mapping with Mobile Lidar and GPR
Governments are beginning to mandate that underground infrastructure mapping be carried out as national policy.
Underground infrastructure mapping of utilities and other infrastructure is one of the major challenges in creating a digital twin at the municipal, regional, and national level. LiDAR reality capture of the above-ground ground features simultaneously with ground penetrating radar (GPR) scans of subsurface infrastructure at highway speeds is bringing the vision of unified 3D models of above and below-ground infrastructure for entire cities, regions and nations closer to reality.
Uncertainty in the location of underground utilities costs the U.S. economy at least $50 billion annually, plus 1906 injuries and 421 deaths over the past 20 years. According to the Federal Highway Authority (FHWA) missing or inaccurate information about the location of underground utilities is a leading cause of highway construction delays. To address the risk of liabilities associated with unknown or inaccurately located underground utilities, contractors regularly increase bid costs by a minimum of 10-30%. Knowing where things are underground has become important enough that in several countries around the world – France, the Netherlands, Singapore, U,K. and the U.S., initiatives to create national digital twins of above and below-ground infrastructure are already underway.
An example of the impact of poor information about the location of underground utilities can be seen in the Sydney Light Rail Project which is a $2.1 billion PPP project for a 12 km of light rail extension in Sydney, Australia to be completed by 2019. In preparation for construction a year was allocated for identifying potentially conflicting utilities in the proposed right of way. About 500 subsurface utilities were identified and scheduled for relocation. During construction a further 400 unmapped utility services were encountered. An economic impact study by an independent consulting firm estimated that the project could have been completed at least one and a half years sooner if a complete and reliable 3D underground infrastructure mapping of underground infrastructure had been available at the project planning stage.
In the U.S. the Common Ground Alliance (CGA) reports that there were 390,366 documented underground utility hits in 2016. The average direct damage cost was found to be $4,021 per hit. The CGA estimates conservatively that the direct cost to the U.S. economy was $1.5 billion. If indirect and social costs are included the total estimated impact of unknown or poorly located underground infrastructure mapping on the U.S. economy is at least $50 billion.
University research has put a dollar figure on the benefits of accurate location data for underground utilities. In 2007, the Pennsylvania Department of Transport commissioned Pennsylvania State University to study the savings on ten randomly selected PennDOT projects. The study found a return on investment of US $21.00 saved for every US $1.00 spent on improving the quality level of underground infrastructure mapping information.
Investment is Key
Until recently construction has been among the lowest industries with respect to investment in research and development, but there are signs that this is changing. In the last few years the number of startups focused on technological innovation in construction has risen dramatically. As evidence of increasing investment in the underground detection sector Hexagon, which has revenue of $4 billion annually, acquired IDS (Ingegneria dei Sistemi) GeoRadar. GeoRadar was the first to combine mobile LiDAR with ground penetrating radar in a towed rig. A software company, Bentley Geosystems, which earns about $1 billion in annual revenue, has developed software specifically for managing underground infrastructure location information.
In 2018 a technical advancement in detection was reported that brings the cost-effective mapping of underground infrastructure at the municipal, regional, and national level closer to feasibility. A successful proof of concept was reported by DGT Associates in Mississauga, Ontario in which data collected by a Siteco rig combining a Faro mobile LiDAR scanner and Sensors and Software GPR arrays collected data simultaneously above and below ground at roadway speeds of 80 to 90 km/hr. Siteco software makes it possible to visualize above ground LiDAR imagery side by side with below-ground GPR scans and digital as-builts making it possible to create 3D maps of underground utilities completely in the office. The process, which does not require boots on the pavement, is much safer than the standard process of walking the route with a wand or push cart and is much more rapid.
The Digital Twin
In the UK the conjunction of three UK government reports, Industrial Strategy Building A Britain For the Future, Transforming Infrastructure Performance, and Data for the Public Good, is spearheading the transformation in how infrastructure is built, managed and operated. Based on the foundation concept that for managing national infrastructure a digital model is equally important as the physical assets themselves, the reports identify developing a national digital twin, which includes above and below ground assets, as an essential goal for the UK government.
In 2012 France embarked on a nation-wide multi-billion euro project to improve the quality of the location information about national underground utility infrastructure. A presidential decree mandated that by 2019 the location of critical underground infrastructure in urban areas will be mapped to 40 cm or better. Furthermore, by 2026 the location of all of the nation’s infrastructure will be mapped to the same accuracy.
In the Netherlands in 2015 the States General passed legislation mandating a “Key Registry for the Subsurface” or Basisregistratie Ondergrond (BRO). It requires that beginning in 2018 whenever excavation is performed, information about subsurface conditions must be reported to the Key Registry. This includes information about subsurface utilities and geology. The primary objective of the legislation is to enable sharing the information that is routinely discovered during construction projects.
In Singapore, the Urban Redevelopment Authority is planning to have a master plan of Singapore’s underground spaces ready by 2019. It will be released as part of the next Master Plan guiding Singapore’s development in the medium term.
In the U.S., an initiative has just been started to create a national infrastructure map which would include subsurface infrastructure. At a special summit in Arizona leaders in public administration, infrastructure development, geography, GIS, and data integration/open data reviewed the current state of location-based information on national infrastructure including subsurface infrastructure. The aim of the summit was to examine efforts to integrate location based data systems across jurisdictions, to understand stakeholder community’s perspectives, to identify strategies for more systematic access to data at the national scale, and to discuss the role of government to implement such strategies.
Taken together, the technical advancement of combining above-ground mobile LiDAR with underground GPR detection which make cost-efficient 3D mapping of the underground increasingly feasible and the growing public awareness of the risks and costs associated with not knowing where utilities and other underground infrastructure are located, are leading to accelerating momentum to create a digital twin of the subsurface at the municipal, regional and national levels.
by Geoff Zeiss, Principal, Between The Poles
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