3D mapping

The commercial, safety and community benefits for using ground penetrating radar (GPR) for the detection of underground assets, in particular utilities, is well-proven. So much so that utility locators now consider the technology a vital part of their toolkit.

Currently in Australia, GPR surveys are often conducted using hand-pushed systems to confirm and/or locate the position of underground assets. Once located, asset locations are marked using spray paint. Sometimes locations are collected using global positioning satellite or via other means for further use in computer-assisted design or geographic information systems.

But the companies that store the information typically do not share this information publicly. This means that once an area is surveyed, and the paint marks wash away, the information is essentially lost, resulting in areas being surveyed multiple times at considerable social, environmental and economic cost.

In recent years, advances in electronics and computer processing speed has enabled full 3D capture of underground assets using arrays of multi-frequency, multi-polarised GPR antenna towed by vehicles, allowing large areas of shallow and deep utilities to be rapidly mapped. Arrays of antennas allow utility signatures called hyperbolas to be traced across each antenna. These hyperbolic signatures line up across the array to show the extent and orientation of buried pipes.

Arrays therefore make it easier to determine the difference between, for example, a buried rock, which may also produce a single hyperbola signature, and the linear feature of an actual buried utility. This not only makes interpretation easier but also more accurate.

Looking ahead with One Vision

Ingeneria Dei Sistemi (IDS) has developed a revolutionary real time mapping software for its suite of array GPR systems. The One Vision software, in conjunction with the IDS Stream EM massive array GPR system, is specifically designed to assist the utility locating industry by providing a real time 3D view of the subsurface over large areas.

Companies involved in large-scale construction projects can now be provided with super clear geo-referenced imagery of subsurface features over large areas whilst still on-site, allowing them to make preliminary decisions quickly and without significant delay to their operations.

This rapid capture and real time 3D viewing capability thus provides a strong case for a more coordinated capture of underground asset location across utility organisations for centralised and coordinated management and improvement of the efficiency of construction activities. It also complements the push for above-ground asset capture using mobile 3D laser scanning (LiDAR) technology to bring a complete mobile mapping solution for both above and below ground assets.

The coordinated capture of LiDAR and GPR also provides more context to the GPR data as above ground features such as fire hydrants, gas markers and electricity substations can be linked to pipes identified by GPR and preliminary assessment of pipe type verified through potholing.