New Zealand-based company creates detailed 3D maps of underground utilities
A few weeks ago, I was tagged in a tweet by my friend T.J. It was this one, about an underground utility mapping project that had recently been completed in Wellington; the capital city of New Zealand, and the place I currently call home. The accompanying image was of a dense network of brightly colored squiggles – each color representing a different type of utility – buried beneath a busy thoroughfare. This mapping survey was a key part of the preparation for a major infrastructure project called Let’s Get Wellington Moving. LGWM’s overall goal is to improve transit across the oft-congested capital, through prioritized investments in sustainable mass transit services and walking and cycling infrastructure, as well as closing off some streets to private vehicles (à la Paris). If you’re a regular reader of my column, you might guess that I’m pretty excited by this prospect.
But back to the utilities. Long before you can start digging up roads and constructing surface infrastructure like light rail, you need to get a detailed understanding of what’s happening in the subsurface. Where are the water and gas ducts? What size are those pipes, and what material are they made from? What about electricity cables and telecom fibers? Is there anything there that shouldn’t be?
Getting answers to these questions isn’t as straightforward as you might expect. On all projects, the information is gathered in a piecemeal manner. The first step is a discussion with all of the relevant network utility operators. If they have a piece of infrastructure passing through the area of interest, they’re asked to provide plans and schematics for it. Local councils or state bodies typically have their own records for the area too, so, they’re also reviewed during the project planning stage.
In some cases, this data is provided as CAD drawings or GIS data. But surprisingly often, these plans exist only as PDFs. And if that wasn’t bad enough, the PDFs can be just a scanned copy of a printed image, occasionally annotated by hand. When Sam Wiffen showed me an example of one of these documents, my jaw dropped. “That is the correct facial expression,” he said, laughing. “You can see this line here? They’ve just drawn that on with a highlighter pen. And there’s nothing on this drawing about depth. That’s a standard process now.”
Wiffen is the CEO and Founder of Reveal, the Wellington-based company who produced the 3D underground utilities maps that had caught my eye on Twitter. I’d been introduced to them by Regional Councilor Thomas Nash, and was now sitting in the Reveal boardroom, getting a tour of their mapping platform. The Wellington surveys have been described as “…the most comprehensive underground utility model in the world (by a large margin)”, so I wanted to learn more about how it all came together.
For Reveal, the first step is a ground penetrating radar (GPR) survey. “We use an ultra-wide band, multi antenna towable radar array,” explained Chief Technology Officer, Tim Rastall, as he showed me a photo of their system. “That’s one of the first things we apply to these sites. It’s a way to triage the state of the subsurface; to quickly assess what’s there.” Their system can collect radar data at 15 km/hr.
GPR works by emitting pulses of high frequency radio waves into the ground and detecting any reflections that return. Just like with visible light, radar waves reflect when they hit an object, and they can cast shadows behind objects. Unlike visible light, radar waves can also pass through many materials. The degree to which the waves are distorted by that material depends on how electrically conductive or insulating the material is. Metals, for example, tend to look especially ‘bright’ on radargrams. The depth to which a GPR can ‘see’, and the intensity of the reflection both depend on lots of different factors, including the signal frequency and the composition of the soil.
All of these interactions combine to produce a raw signal that, on first glance, looks chaotic and full of noise. But for Wiffen and Rastall, it’s a treasure trove of valuable data. With careful processing and analysis, that signal can be unpacked to provide a variety of information, from the pavement thickness to the presence of voids. During one survey, they even managed to find forgotten tram tracks buried under one of Wellington’s busiest streets.
But of course, what Reveal is most interested in is mapping utility networks. So, once they’ve collected their radar data, they first set out to compare it to the information provided by the utility operators and local councils. In some instances, they might also access aerial imagery. They get out into the field too. Wiffen showed me some high-resolutions photos they’d taken in a telecoms box, and LIDAR scans of the interior of a stormwater access chamber. They also take georeferenced photos of any open trenches on the project site, and add those to their data stream.
[An aside: Something I didn’t realize is that the ducts that hold subsurface utilities are color-coded, though, as Rastall explains, “They’re not always consistent in how they label services. Gas is usually yellow, telecoms are regularly green, and power is almost always orange.” Coding them in this way means that when someone breaks ground and finds a duct, they should be able to identify its contents at a glance. This color coding extends to the surface too. Here in New Zealand, if you see a blue spray-painted marking on a footpath alongside the letter ‘W’, that’s telling you that somewhere beneath that spot, there’s a water pipe.]
The results don’t always match. “Everywhere we go, both within New Zealand and internationally, we see this inconsistency between what is in the documents and what is actually in the ground,” says Rastall. In one of the maps we explored during the interview, a key telecom line could be seen to be almost five meters further East than had been recorded in the official schematic.
Part of the reason for this is that on a plan, an electricity mains will only be visualized as a 1D line, or a telecom box as a single point. In reality, these objects exist in a complex 3D space. In addition, as Rastall explains, “many of these assets were put in before GPS was really an everyday thing. So, the way that they’d document a position relied on using a measurement from a surface or an edge. Those features can move or be changed over time. They’re not a reliable reference.”
Having outdated, inaccurate or incomplete information about subsurface utilities is not just inconvenient for a construction project. It can lead to delays and budget blowouts.
During the planning phase of the Sydney Light Rail project, the state’s Department of Transport mapped 5,000 subsurface utilities using a traditional potholing approach – effectively, drilling a series of exploratory holes along the 12km route to see what was there. From that, they identified 500 lines that would need to be rerouted to make space for the new track bed. However, a year into the construction phase, they’d uncovered a further 400 utilities that hadn’t appeared in the data gathered from utility providers, nor from their pothole survey.
Every one of those unknown utilities had to be treated as ‘live’, until further information could be gathered. As a spokesperson for the state’s transport agency explained to ABC in 2016, this caused delays and cost the project money, “For every redundant utility find, we have to go through a two- to four-week process to validate it, because if we snip it, something really bad could happen”.
This prompted the project managers to undertake radar-based mapping along the route – similar to the tech used by Reveal. The result was a more detailed view of what lay beneath Sydney streets. After that, the project experienced few (if any) subterranean surprises. Australian consulting firm ACIL Allen, who carried out a review of the project, concluded that had a complete 3D map of underground infrastructure been available at the planning stage, the project could have been completed 18 months earlier, at a lower cost, and with a much lower level of risk.
“That’s why our customers come to us. They don’t want to be hitting utilities and experiencing project delays,” says Wiffen. “With LGWM, we brought activity right to the front – getting out there early and mapping everything. That way, the project’s team ends up being much better informed, long before construction starts.”
What Reveal produce for their customers is a far cry from a highlighted piece of paper. It is a visually-rich, interactive online tool that can selectively display layers of data from different sources. Users can toggle between those layers, depending on their priorities and needs, but all of the information is there, stored in one place. It’s also provided in a way that conforms to international standards, as defined by the Open Geospatial Consortium. “It didn’t make sense for us to start from scratch when it comes to data formats. We wanted to make sure we’d have good interoperability with a lot of our stakeholders in how we describe a three-dimensional object underground,” says Rastall.
Their offering seems to be attracting attention. As well as Wellington, Reveal are currently working on large construction projects in Australia and in Singapore. Wiffen tells me they’re also in conversation with two major utility operators in the US and the Chicago Department of Transport. “The thing is, we aren’t just some startup tech company. We’ve been doing this for a long time – more than 10 years. We’ve got a lot of incredibly smart people here; not just geophysicists, but engineers, scientists, IoT specialists, surveyors. Some of our team come from the trenches – they’re ‘boots on the ground’ people. That’s where I’m from too. Our knowledge comes from a deep-seated understanding of the problems in the underground. We’re in this for the long haul.”