The complete digital site is more than just machine-controlled heavy equipment. Recent advances in heavy civil have been profound in connectivity, automation, and visualization.
This heavy excavator (above) resolves orientation via GNSS antennas on the counterweight, and a series of tilt sensors calibrated to the moving sections of the boom provide highly accurate feedback to the operator as to progress of the bucket towards design grades per the 3D model uploaded into the controller. Another level of productivity gains comes from the telemetry fed into the site-management software and its virtual-reality viewing tools that provide real-time visual status of all equipment on the site.
How long has automation played a role in heavy civil construction? As far back as the late 1980s when early GPS-guided (or informed) systems began to reach the market. But it goes even farther back if you consider the use of radio-controlled equipment and operator-feedback systems from the 1930s.
In the eyes of many, the state of heavy civil automation appears to have plateaued. Talk of autonomous bulldozers may no longer elicit a “wow” response even from the layman. But there is more than meets the eye. What is the current state of automation in heavy civil?
There have been a lot of lateral advances and new resources to apply to the machine-control foundation: powerful mobile processing, ubiquitous internet, a more tech-savvy workforce, the cloud, and advanced visualization tools, mobile mapping systems, and even UAS—as well as advances in the foundational machine control systems.
Today’s digital site now encompasses not only high-precision positioning, but also asset and workflow management informed by real-time metrics. The complete digital site is now at hand and has been successfully implemented by forward-thinking firms worldwide. Borrowing from industries like manufacturing, where automation has become not only possible but expected, and from the BIM (building information management) processes, heavy civil is coming out of the economic downturn into a new era of efficiency.
The complete digital site benefits not just the client and prime contractor; you do not have to be a mega-firm to be able to afford the whole shebang to participate. Becoming digital-site-ready (through a few key hardware and software choices) makes a small firm much more attractive as a sub-contractor candidate or small-cap project bidder. Many of the digital-site elements developed for heavy civil have utility for surveying and vice versa.
To explore just how digital heavy-civil sites have become, we attended site training recently put on by Topcon Positioning and Brandt Tractor, a prominent Canadian dealer for construction and agriculture equipment and solutions.
No Eyepiece
For elements of a heavy civil site that cannot be laid out by machine control, old-school point-by-point stakeout or grade staking is performed—horizontal and/or vertical. The robotic total station (working from digital models, alignments, and point files developed in the design phase) has greatly improved efficiency in layout. Depending on the task and scope of project, the layout might be done with a simple total station (with a digital readout and a digital model on board or in a data collector), or increasingly with a robotic total station enabling one-person layout.
More recently the drive for cost-effective and focused workflows has given rise to a new wave of fit-for-task layout instruments and software. Layout can now be done by one person, working from a data collector and tablet (or potentially a phone!) with the layout points in the design loaded on-board or directly from the cloud.
Some of these instruments have no eyepiece; the user is directed to point in the layout software and/or can view what the instrument sees via a video feed on the mobile device. An example is the Topcon LN-100 Layout Navigator. It is a robotic total station, though it does not look like it at first glance as its housing looks more like a construction laser. The instrument has been designed (ruggedized, dust resistant, and self-levelling) for a construction environment; it is designed for one thing—layout—and does it very well.
What looks like a construction laser is actually a high-precision robotic total station, optimized for site conditions, that can be operated from conventional data collectors as well as multiple types of mobile devices and tablets. The operator sites through the video camera on the total station—no onboard optical eyepiece.
The Cycle
Nearly any element of heavy-civil infrastructure, from inception to commissioning and through its entire lifespan, can be completely managed for all phases through a single digital workflow. A firm may be involved in only one or a few of the following phases: mapping, needs analysis, preliminary survey, design, layout, mass excavation, bulk earthworks, fine grading, paving and compaction, as-built and inspection, commissioning, operations, repair, and rehabilitation.
The good news is that smooth workflow management can be maintained throughout. Connectivity can be maintained between phases at the levels of compatibility (at the very least, data formats can be exchanged), interoperable (no conversions needed), to fully integrated (shared systems and databases). Let’s look at the state of the digital site in terms of a few core phases of a typical heavy- civil project.
Survey and Design
This site-management software suite receives locations and telemetry from the heavy equipment and connected devices (like GNSS rovers and total stations) on the site and offers a virtual reality view of the site.
Preliminary surveys can be performed with UAS (see “UAS and Mobile Mapping” below), scanners, mobile-mapping systems, close-range photogrammetry, aerial mapping, GNSS rovers, and total stations and robotic total stations. For some tasks, a 1-second or even 0.5-seccond total station may be warranted—fully robotic total station, reflectorless and with video control—this is commonplace.
But there are entire lines of fit-for-purpose total stations all the way down to simple non-motorized units with simple digital readouts still ready for a digital site. And efficiency is gained in having the data-collector software being in the same suite as the office software. Digital-site-integrated robotic total stations are specifically designed for layout (see “No Eyepiece” on the previous page).
Multiple surveying instruments and sites can be managed in suites like Topcon’s MAGNET Enterprise. It is the same operational model as Topcon Sitelink for the instruments, heavy equipment, and data for a construction site (or multiple sites), but more on that below. The instruments themselves can be monitored for firmware, usage, error messages, and even remotely “locked” if stolen (thanks to built-in devices that can be connected via cellular technology). Every instrument of the site(s) is connected, and the data flow can run through these cloud-based suites.
Design to Field
While the lion’s share of civil design is done in environments like Autodesk and MicroStation, suites like MAGNET Office have their own CAD engines—not designed for full-scale civil design, but more for developing stakeout, models for layout and machine control, and processing and reduction of data. Data transfer from design CAD are typically focused; only the relevant information and models are transferred using DWG, DGN, DXF, or XML formats. Gone are the problems with transferring only ASCII point files. The data is managed in one suite for field and office—and via the cloud.
Software in one family or line shares common elements but can be offered in different flavors, simplified to be fit for purpose to streamline and eliminate overhead in training and experience needed to operate. Continuing the same example, Topcon’s MAGNET Field is the full, survey-grade product, complete with full cogo functionality.
But folks such as grade checkers who don’t need the full functionality can choose MAGNET Field Site; here they have limited cogo but can extract the grades they need from the surface models on the data collector directly to their GNSS rovers or total stations. The concrete layout team on the site could choose another version, MAGNET Field Layout. A version called MAGNET Construct can run on an Android device, is free, and can import DXF, DGN, or ASCII from which the layout points can be extracted. A further simple graphical interface that runs on Win or Win Mobile is
Pocket3D, simple functions for layout.
There is quite a labyrinth of solutions to navigate, but the punchline is that this trend towards focused, streamlined, fit-for-task solutions means that every task can benefit from and be integrated into the digital site with a minimum (but appropriate) amount of training and investment.
UAS and Mobile Mapping
It is not uncommon to see UAS and mobile mapping systems deployed at heavy-civil sites, and not just for pre-design surveys. Rough estimation and eyeballing are no longer acceptable in mass earthworks or bulk grading; timely volumes and progress towards design grades are often demanded in near-real-time.
A UAS can fly a site and produce a point cloud and/or digital elevation model (DEM) within an hour depending on site size, as can a scanner or mobile mapping system (with lidar and/or close-range photogrammetry). The most common uses for UAS heavy civil are volumes (especially good for irregular piles), total site earthwork compliance, as-built for bulk grading, and to check profiles and slopes.
UAS, terrestrial scanners, and mobile mapping systems are becoming commonplace on large civil sites for pre-construction and as-built surveys, compliance and volumes, and site visualization.
We looked at a UAS that has been deployed and integrated into digital site workflows, the Sirius Pro fixed-wing UAS that uses MAVinci flight-control software. Offered in the Topcon Positioning Systems product line, a full dual-frequency RTK receiver has been integrated into the craft and can receive RTK corrections from, and work on the same control framework as, the RTK base deployed on the job site or RTK network (providing corrections for the GPS on the heavy equipment). This can (for most uses) eliminate the need to set ground control points, though those can be set by the user for specific situations.
This hand-launched UAS flies low, and the relative accuracy of the images and downstream point cloud or DTM/DEM is generally 2-5cm, depending on height of flightpath above the ground. Flightpaths are handled by the autopilot and flown in alternating swaths (sequential would require more time to go out farther at the ends to affect a tight turn).
I noticed that the design of the Sirius looks a lot like the high-wing single-engine private aircraft you might commonly see. I was informed that the design was chosen for the same reasons: stability, short take-off and landing, and the ability to come down safely for the rare occasions of power loss (it can work well even “dead stick” or if there is still enough power to operate the control surfaces for a guided landing). The craft can fly in strong winds at a typical cruise speed of 65km per hour, covering a large site quickly on a single charge.
Being airborne has an added GNSS-quality dividend. The antenna don’t need to be large or have a large ground plane: there are practically no sources of multipath to deal with up there. The relatively small antenna and RTK board (that draws little power) are well suited for a lightweight UAS.
Of course, the RTK on a moving craft will yield lower accuracy than a stationary rover on the ground, but as the absolute position of the model is generally of less importance (in mass excavation and bulk grading) the use of ground targets is often unnecessary. I have done RTK check shots on UAS-derived topo models and have found the differences to be within centimeters horizontally and vertically in clear sky conditions. There is a lot of potential in this arena for heavy civil.
Terrestrial mobile mapping systems are utilized in heavy civil for many of the same uses as a UAS: volumes, as-built, and checking profiles and slopes, but with the addition of laser scanning to the photogrammetry. RTK and post-processed kinematic provide pretty good positions through which the scanning and images can be registered, and IMU is added to maintain positions between typical GNSS 10Hz observation epochs and when the sky view is obstructed. A DMI (speed measured on a device attached to one of the vehicle’s wheels) provides velocity augmenting the GNSS and IMU solution and for applications that use distance travelled (as opposed to time) for image capture.
Ground targets can be deployed if higher accuracies are required, and/or positions of visible and suitable well-defined objects can be applied after the fact, if need be. For most applications, the relative accuracy is of higher importance, and absolute position may hold little value.
For non-heavy civil uses where mobile mapping systems are commonly deployed, such as asset inventory (signs, utilities, street channelization markings, vegetation clearances, etc.), the GNSS/IMU/DMI solutions without ground targets typically suffice. There are issues with crossing paths; often there are minor differences in position and elevation, even with post-processed kinematics. For these instances, various simultaneous localization and mapping (SLAM) approaches are employed.
Typically, this involves finding observed features common to both routes, analyzing the respective RMS, and determining what adjustments to make. Newer mobile-mapping systems typically scan at one-million+ points per second at up to about 100m but provide the best results at 60m or less, providing high relative precision in a 120m swath along the driven route.
The Internet of (Site) Things
We hear a lot about the Internet of Things (IoT), and while things like IoT-enabled toothbrushes might raise a skeptical eyebrow, the ubiquitous connectivity of every instrument and piece of heavy equipment on a construction site brings real and quantifiable cost benefit. To become part of this “neural network” for the site, instruments, data collectors, machine-control modules, and sensors communicate with each other by WiFi, long-and-short range Bluetooth, and spread-spectrum and UHF radios.
Continuing with the Topcon example, their Sitelink3D and Sitelink3D Enterprise provide the connectivity hub to communicate with, manage, and support instruments and sensors. Valuable equipment usage and health data can be received (hours of usage, idle time, and firmware versions, number of specified actions completed); field personnel can even send instructions and messages via the linked data collectors and machine controllers. There are safety benefits as well—the live positions and identities of these connected devices create a model of proximal and situational awareness.
The cloud provides the live link between field and office—no more fumbling with thumb drives and the cumbersome uploading and downloading of data. It seems a shame to design in a full 3D environment and then have to distill the design down to simple ASCII point files and have to deliver them manually by “sneaker-net.” You have a site and design environment working in one reference framework, and the cloud allows the field and office to work in what is essentially one digital database.
Elevation Matters
On the heavy civil site, in grading, paving, and layout, high-precision vertical is generally more critical and is traditionally more costly and harder to achieve than horizontal positions. For machine guidance and (for instance) blade or shovel control, base-rover GNSS can deliver sufficiently high-precision horizontal positions in real-time for nearly all needs. But by nature the vertical precision of GNSS is generally twice (or more) as imprecise as horizontal results.
A number of approaches are employed to directly, terrestrially provide high-precision vertical in real-time, like a simple rotating laser and a tall sensor bar on the heavy equipment, or a robotic total station with a smart prism or other sensor on the GNSS rover or fixture on the heavy equipment.
One unique variation on the approach of a rotating laser is Topcon’s popular Millimeter GPS system. The laser, set on a tripod at the site, emits a kind of laser “wall” about 10m high. Companion positioning zone sensors fixed to a GNSS rover or features of a grader or paver (shown at right) sense this wall of a Z-shaped laser pattern and can determine the respective elevation. The resultant elevation can be in the millimeter range inside a zone of about 300m and cm range beyond that to as much as another 1000m (depending on local conditions).
Virtual Reality
Now that the entire site is “wired,” the next level of productivity tools can truly take off: live management of the site and into virtual reality (VR). I saw a demo of Topcon’s new Siteview solution on a workstation facing out over a busy construction site, and the equipment (and earthworks progress) was faithfully represented in 3D. The equipment was moving at a corresponding rate on the screen; you can even choose to view the site from the viewpoint of an operator in any of the equipment connected on the site, even from the point of view of a grade checker carrying a rover. The view can be switched to another site, in another part of town, state or province, or even another country.
As impressive as the visualization is (and there is talk of running such VR tools for construction on things like Oculus goggles), the real payoff for management of the site is in the streams of live data from the instruments and heavy equipment. Site progress can be monitored live: tallies, number of passes completed, total volumes moved, and how efficiently the equipment is being used. You can view the earthwork models in the same software with progress superimposed next to numerical tallies.
The machine-controlled equipment that act as the live appendages of this digital site fall into two main categories: indicate systems and hydraulic control. An example of a simple indicate device is a counter for hauling trucks that plugs into a cigarette lighter. Using the built-in GPS, the device knows when it has entered a geo-fenced location like a designated load spot and a designated dump spot. After the trucks have completed each run from one to another, this provides a much more reliable count than the manual clickers—a few miscounted loads a day can add up.
Other indicate systems show the equipment operator the progress towards meeting the design per the 3D model loaded into the controller, but they still operate the equipment components. Then there are controllers that connect to the equipment’s hydraulics, operating the booms, buckets, blades, and even steering. The position of the equipment and its many moving components requires combinations of GNSS, laser receptors (e.g. prisms and the millimeter zone sensors, see “Elevation Matters”), accelerometers, tilt sensors, and more.
To determine orientation, two GNSS can be deployed on a single post or, as in the case of excavators, on opposite sides of the counter weight or on both ends of a blade of a grader or dozer. Topcon now adds high-rate IMUs for equipment pitch and roll as well as blade orientation.
The cost benefit of machine control includes completing tasks to design dimensions quickly, without rework, and not having to set stakes or wait for a grade checker. These benefits generally stand without question. But how can you manage scores of heavy equipment on a site or multiple sites in real time? Every piece of heavy equipment, instruments, sensors, data collectors, and machine controllers, every task performed by the field personnel using fit-for-task scalable solutions—including those of sub-contractors—these can all be part of the fabric of the complete digital site.