Drones in construction and infrastructure
Why and how to use drones in construction and infrastructure
According to a McKinsey study, the construction industry struggles with a great deal of inefficiency. Large construction projects typically take 20% longer than expected to complete and are up to 80% over budget.
Compared to other sectors, the industry has been slow in embracing new digital technologies, even though the long-term benefits are significant. It is time for disruption. And according to the study, commercial drones—or unmanned aerial vehicles (UAVs)—are key to this.
Some construction companies have already jumped on the professional drone bandwagon. In 2018, this sector saw a 239% increase in the adoption of drone technology. In its report on the impact of drones, PwC states that the use of drones throughout a construction project provides an unparalleled record of all activities; cuts planning and survey costs; increases efficiency and accuracy, and eliminates disputes over the status of a project at a given point in time. No wonder a drone program is currently a terrific investment for construction companies.
We will use practical examples from the following case studies to illustrate the benefits and applications of drones in construction. All these cases involve the use of the WingtraOne surveying drone.
Pre-construction and design
Earth work and construction
Maintenance and inspection
How is drone data used in the construction industry?
A drone is mainly used in the construction industry for surveying and inspection purposes. Drones are equipped with downward-facing sensors, such as RGB, multispectral, thermal or LIDAR, and they can capture a great deal of aerial data in a short time.
Getting real-world insights with photogrammetry
During an aerial drone survey with an RGB camera, the ground, its features and buildings are photographed multiple times from different angles, and each image is tagged with coordinates. First, these highly detailed geotagged images can be used for assets and inspections, for example, of building roofs or hard-to-reach areas. They can also be used to monitor areas across long distances, such as vegetation rows, roads and railroads.
Taking the technology a step further, photogrammetry software can combine the images to generate geo-referenced 2D maps, elevations and 3D models. These maps can be used to extract information such as precise distances, surface and volumetric measurements.
Who has the most to gain from drone technology?
This stretch of road (7 km, 4.3 miles) was captured in a single flight with the WingtraOne drone using its corridor mapping feature.
The complexity and scale of such projects exposes them to many challenges this technology can help solve, including long and costly surveys, early identification of construction mistakes, penalties for missing deadlines, miscommunication between stakeholders and contractors, and volumetric assessment. It can also help stakeholders efficiently survey to avoid financial liabilities post-construction due to lack of maintenance and resultant damage to the environment.
Drones can also open up new applications that were previously very hard or costly to access or closely track. Think of monitoring or inspecting hard-to-reach areas or of analyzing and optimizing rapidly changing environments such as construction sites.
CHAPTER 1
Six benefits of using drones for construction and infrastructure projects
The first and most obvious benefit of drones in the construction industry is the ability to obtain precise visual data of a site faster and cheaper than with terrestrial techniques or manned aircrafts. However that’s only one of the many benefits drones can bring to construction companies.
1. Fast, reproducible, on-demand image acquisition
On a construction site, there is always a contractor, an engineering company, an earthmoving company and a number of subcontractors to execute specialized work. In addition to involving a lot of teams, deadlines are tight and require frequently-updated records to drive decisions and align multiple stakeholders.
This is where a major advantage of drones lies for construction site managers. Drones provide a complete picture of the construction site on-demand and within a few hours.
The sharp, detailed images produced by drones enable site managers to track work progress and make accurate decisions based on up-to-date data and comprehensive reconstructed site maps instead of relying on plans or incomplete data that may not reflect reality.
The aerial images also act as a visual aid when communicating with all parties, so that everyone can see for themselves what has already been done and what remains to be done.
2. Accurate and comprehensive data
In addition to having detailed aerial photographs, the same data collected by a drone in a single flight provides a complete map of the site with GPS points, in 2D and 3D. These maps allow accurate measurements of distances, surfaces, elevations and volumes. From there, photogrammetry software also generates elevation models such as digital terrain models (DTMs) and digital surface models (DSMs).
With drones, you no longer need to go back to a job site if a data point has been missed. Bacon Farmer Workman (BFW) is an engineering and surveying company in the US Midwest delivering high-quality surveys for clients in construction: “It used to be the case that there would be a landmark, like a manhole, that was missed in a survey. And they’d need the location of it, so someone would have to drive out, set up equipment and get the coordinates of it.” explains Jacob Cash, Mobile Mapping and LiDAR Department Manager at BFW.
3. Cost and time saving
Drones significantly reduce time-intensive data collection in the field and its associated labor costs. Hades Geodeesia, a 30-year-old surveying company is using drones to provide accurate survey data for the construction of a major highway in Estonia: “It doesn’t make sense to go outside and walk for three to four hours and get about 500 points and make calculations.” said Vaiko Veeleid, CEO of Hades Geodeesia.
Fly-through of a 22 km (13.7 mi)-long road. The generated point cloud contains 1.2 billion of points, with a GSD of 1.2 cm/px (0.4 in/px) allowing for precise measurements. It took nine hours with a WingtraOne drone to collect this data in the field.
Large public works in Norway also benefit a lot from this technology. The Norwegian Public Roads Administration started using drones for regular surveys during road construction.
In the end, drone data saves time and money across all stages of a construction project and for a range of reasons that could be folded into any of the six benefits listed.
4. Better documentation and faster reconciliation with subcontractors
Easy and repeated surveying means that the site will have more complete documentation throughout its life cycle.
In cases where a project progresses on top of faulty construction, it’s difficult if not impossible to trace where the mistake was made or who made it. Drone data provides clear, accurate and retrievable documentation at frequent points in the construction process. This allows stakeholders to review and pinpoint where mistakes occurred and settle these disputes out of court since the evidence is clearer.
Another benefit of better documentation is that the data collected can be analyzed to draw lessons from it and compare it for benchmarking purposes.
5. Remote access to current status of the site
BIM managers, surveyors and managers in head offices currently have to either travel physically or rely on workers on site to get information about construction progress. By having somebody on site flying the drone and capturing images, you will be able to see the progress of projects directly on your computer, to evaluate it and discuss it with site managers as if you were on site.
In this way, drones allow managers to have a light point of contact on the activities of their business units in several countries or regions and to obtain information that you would not normally be able to obtain without traveling, or the good will of other individuals.
6. Increased safety
Being able to monitor and inspect hard-to-reach places or areas in the middle of machinery without entering them obviously reduces workers’ exposure to accidents.
Add to this that safety on a construction site is also about securing the work area as accessible only to qualified personnel. So drone imagery can help to locate a breach in the perimeter of a site more quickly, preventing civilian entry and potential accidents.
But the greatest improvements in safety can be found in inspections and maintenance work. Instead of climbing electric poles, using ropes to inspect features of a facility, or working along busy highways, workers can fly a drone and inspect images without putting themselves at risk.
CHAPTER 2
Drone applications throughout the construction cycle
Drone data is so versatile, it can be used throughout the entire construction lifecycle, from feasibility and tendering to delivery and maintenance.
1. Bidding and pre-planning
Even before the launch of many construction projects, a topographic survey of the site is required to get a good understanding of the environment in which the project will take place. DTMs and DSMs of a site generated with drone data can show possible drainage points, changes in elevation and other factors that can assist in selecting the best locations for building, digging or storing materials.
2. Planning and design
The very same images collected by drones can then be used as part of the planning process, providing the foundation for the work of others, such as architects, local authorities and engineers.
With drone orthophotos and 3D models, you can overlay buildings onto their environment to get a clear sense of how a new building might look next to an existing one. You can assess how the new project will impact the area from both a practical and an aesthetic viewpoint. 3D models also allow analysis and visualization of cast shadows and outlooks/views. You can also extract precise data such as curbs or manholes measurements and import them into your CAD or GIS software to enrich existing data.
Because a whole project is based on geospatial data, it has to be accurate. This is also an area where drone data shines. As an example, we could take the construction of EuroTube, the very first test track for the European super-fast transportation system. The team used drones to conduct a survey of the site.
“The dataset gathered by the drone was precise enough to let the engineering office begin planning construction. The generated point cloud has a vertical accuracy of 10 cm (4 inches) and horizontal accuracy of 3 cm (1.2 inches),” said Gerard Güell, the Construction Director of EuroTube.
3. Execution
While it already offers multiple advantages in the planning phase, the greatest value of drone use might come when projects enter the construction phase.
Earthworks
From drone images, you can generate a point cloud consisting of thousands of points, each containing geospatial (X, Y, Z) and color information. Then, with a photogrammetry software, you can get precise volume measurements and run a cut/fill analysis.
Contractors who move earth are paid according to the amount they have moved. So good accuracy when measuring the amount of earth moved is necessary. Highly accurate drone data reduces the margin of error in these calculations, and the payments.
For example, the Norwegian Road Administration hires contractors to build roads. “The drones help us to follow up with the contractors who build the road. We can agree on estimates, how the work will be carried out and the amount to be paid,” Kjellsmoen said. “We have everything they have done in detail, including the amount of debris that has been moved.”
As-built vs. as-design
One of the most striking advantages of accurate site visualization is the ability to overlay the CAD on the orthophoto. This allows you to compare what was actually built with the plan and make sure that they fit together. Site managers can then identify differences between planned and real-time progress and steer projects accordingly.
Site progress monitoring
During the construction phase, site managers have to control and validate completed work in order to permit continued work. The faster you are able to check and validate a task, the faster you can move on to the next task, saving time along the overall construction process.
Given the relatively low cost of using a drone to collect visual data on a construction site, it’s possible to carry out surveys on a regular basis and build up a record of progress.
This timeline of information can be used to control and validate tasks more quickly, saving time and ensuring that deadlines are met.
Communication tool
On construction projects, there are often several stakeholders in several locations who are all eager to know how things are progressing.
For this to be possible, stakeholders should visit the site, or hire a prohibitively expensive helicopter to collect aerial photos. And even if they did this, the pictures collected could be out of date by the next business day.
The visual data from regular drone surveys assists in on-demand (could be daily, weekly) operational planning. It furthermore helps in explaining how immediate work should be performed and helps identify safe or hazardous areas.
Visual reports can also be sent to customers, helping them to stay informed about how things are progressing in terms of time and budget.
Minimize rework and litigation documentation
When your project is moving forward, and it reaches a milestone, you want to be sure that everything has been achieved to the highest quality standard. Further construction is based on that milestone, so if something has been done wrong, you’ll eventually get stuck, and you may have to tear down what has been done previously. Having up-to-date visual data can help you catch a mistake before it takes shape and avoids demolition and the waste of time and materials related to it.
And if a mistake happens, and it is built over, you have regular documentation of the process, and you can check back to see where the mistake occurred more precisely and settle disputes without lengthy discussion, or even court cases.
Handover
Detailed documentation presents advantages to both the contractors and the site owner, who will take over responsibility of the project once complete. Specifically, the owner can look carefully through the documentation before agreeing to the handover, and contractors can prove that the work has been conducted as per requirements, including details on who did what.
4. Maintenance and asset inspection
Maintenance is often not a priority because it costs time and money and doesn’t bring much value to operations … at least not when they are running as usual. But as soon as you are faced with a serious problem due to lack of maintenance, you can be held responsible and lose a lot of money.
That said, ensuring quality maintenance of assets is not always easy to do at a reasonable cost. By sending drones in the air, companies can visually inspect large assets or those located in hard-to-reach areas more quickly and cost-effectively.
CHAPTER 3
Drone imagery outputs
1. Orthophotos and orthomosaics
Drone images are corrected for image distortion and stitched together during post-processing to create a highly-accurate orthomosaic map. Each pixel contains 2D geo-information (X, Y) and can directly procure accurate measurements, such as horizontal distances and surfaces. They can be overlaid on projected designs and on blueprints to track site progress, serving as a visual communication tool and site documentation.
2. Point clouds
A densified point cloud can be generated from drone images. Each point contains geospatial (X, Y, Z) and color information. It provides a very accurate model for distance (slant and horizontal), area and volume measurements.
3. Digital surface models (DSMs) and digital terrain model (DTMs)
In DSM and DTM models, each pixel contains 2D information (X, Y) and the altitude (Z value) of the highest point for that position. These models can be used, for example, to determine which part of the site could be flooded should water build up or if you need to hire a contractor to flatten the earth.
4. 3D models
The 3D textured mesh is a reproduction of the edges, faces, vertices and texture of the area shot by the drone. This model is most useful for visual inspection or for when external stakeholder input or public involvement is essential for a project.
5. Raw images
As they have not been processed, raw images offer an even greater level of detail and can be very useful for assets inspection and analysis.
CHAPTER 4
Return on investment: how drones create value
Beyond the initial investment in the equipment, introducing a new tool and workflow in an established organization does cost time and money. So how can professionals in construction offset the initial investments and, even better, get a significant return when investing in drone technology?
Cutting survey costs
The process of mapping a construction site used to be long and expensive. Construction companies undertaking large projects had to spend days and weeks with ground-based instruments or rent a helicopter to fly over their sites to take the necessary photos.
Today, a drone can survey an area in minutes at a very low cost. The Norwegian Public Roads Administration significantly reduced the time and expense of their projects when they started using a WingtraOne drone to carry out regular surveys of road construction:
USD figures estimated conservatively based on ~1000 NOK (108 USD) per hour wage and helicopter flat rate per survey. Both estimates quoted from administration source. Set-up time for the multirotor will be significantly more due to more flights. Multirotor set-up time estimated as a ~2 hour block vs. a ~1 hour block for WingtraOne, conservatively. Post processing for all methods not included, but is less with WingtraOne due to a streamlined post-processing workflow.
Paying contractors
Because contractors have to be paid according to the earth they moved, having accurately measured proof to reconcile contractor’s estimates can mean saving thousands of dollars. Because with drone data, instead of relying on subcontractors measurements and goodwill, you rely on impartial data to reconcile estimates and payments.
Contractors might also miscalculate how long the project would take, because you had to move more earth than planned. So having highly accurate estimates can also avoid project delays and penalties.
Faster decision making
Time is always key in construction projects. Because behind time there is cost. So the faster you can be in getting the data and the information you need to make a business decision, the better. Especially if there are workers “on the clock” waiting for you to make a decision.
By flying a drone and processing the images, you can get data within a few hours instead of days or weeks. You save employee and subcontractor costs and are moving faster to the next task.
Prevent costly misaligned construction
Pre-construction
A lot of money can be saved by using drone data in the initial phase of planning. With the help of the 3D elevation models, you are able to pinpoint challenges during pre-construction and spot mistakes before they happen, saving time and money in the long run.
As an example, let’s look at the case of this energy company that turned to drone data to survey a projected solar farm site in Illinois. Before the survey began, the client already had ideas about where all of their panels and equipment would be placed during and after construction. But from the digital terrain models generated with the drone images, they realized the solar farm would partially flood.
“They saw the visual representation and realized ‘that’s where the elevation drops off, and we’re not going to be able to put anything down in there.’” said Jacob Cash from the full-service engineering company Bacon Farmer Workman, which conducted the drone survey.
Thanks to drone data, the client rearranged their construction plans around the areas that would stay dry all year round, avoiding damage and substantial financial loss.
Execution
During construction, if any part of the structure is built off-plan by just a few centimeters (fraction of an inch), this can cause problems as building continues. The project will lose time and money due to a need to backtrack and possibly demo and rebuild.
Cost of poorly maintained assets
While the value of proper maintenance is not evident in day-to-day operations, if a significant problem occurs and the incident is linked to poor maintenance, it can become a huge financial problem for your company. This is especially the case for large infrastructure that supports human residence or transit, or that could significantly damage the surrounding environment, such as dams, power plants, power lines or retention ponds with toxic waste.
Using the high-resolution images captured by drones, maintenance teams can quickly inspect assets, target wear or damage, and prioritize any needed operations. By doing their work faster and more efficiently, maintenance crews are better at mitigating failures that could have catastrophic environmental and financial consequences.
Post-project documentation
Most construction companies do not do a post-project analysis. They just know how much it costed and how long it took. But with this approach, they don’t have the ability to optimize for future jobs.
With the drone data and the documented changes, it is easy to check what was done at a specific stage. That way you can make better estimates when bidding on a similar project, perhaps making the difference between a bid won or lost.
CHAPTER 5
Roadblocks to tackle
While drone manufacturers improved their reliability and range of sensors, and software companies are making the extraction of data from drone imagery more seamless, there are still a few roadblocks to consider before implementing a drone program.
Ease of operation and maintenance
One of the first problems when investing in drones is having trained staff to operate, manage and maintain them. Some drones require piloting skills and/or others require geo-spatial experts to process data in order to obtain accurate information from images.
Also consider how the drone fits into your workflow and whether your team can get the information they need at the end of the process. Ideally, choose an easy-to-use drone and software with well-integrated sensors and GNSS positioning systems. That way, your existing staff on site will be able to use them on their own and get accurate data from them whenever they need it.
Regulations
Different countries have different regulations on the flight of drones and restrictions around urban areas and certain airspaces. It is easier to fly over a highway in the middle of nowhere, where the risk to people and valuable property is lower in the event of an accident, than on a site in a dense area.
Also, regulations tend to evolve rapidly to meet the requirements of present and future commercial uses. As a construction company, if you want to internalize this capability, you need to ensure that your staff is trained and regularly updated to follow regulations and operate the drones safely.
Try first, scale then
Some contractors would benefit from partnering with a specialized drone service subcontractor. These specialists have the authorizations, the trained pilots and the knowledge to process the data and get the desired insights. They can also ensure that local and national regulations regarding the use of airspace are followed.
Once you’ve proved that the insights from drones bring value to your organization, the next step is to internalize this capacity. There are many reasons for having drones in-house instead of relying on service providers. First, the data could be sensitive and you might prefer having your own team handling it.
Then, it’s a matter of responsiveness. You might not want to ask the service provider to visit the site a week in advance and then wait for the data. You might need the data now to make a decision. So with an internalized capacity, you can go and fly and get the data. And you can do it every week or every day instead of once a month or once a year.
CHAPTER 6
Why is WingtraOne a great fit for construction and infrastructure projects?
Before implementing a drone program, it’s essential to choose the right model for the job. This starts with the choice of a fixed-wing aircraft—offering a longer flight time and therefore a wide coverage—or a rotary aircraft (multi-copter drones), offering the convenience of taking off and landing anywhere.
The WingtraOne VTOL (vertical take-off and landing) combines the best of both worlds, with the added benefit of an easy workflow and well-integrated, high-quality GNSS sensors and positioning systems.
Speed and large coverage
Many construction sites tend to use multicopters, because the initial investment is low. Also their ability to fly around a building or around infrastructure, such as a bridge, makes them excellent tools for small-scale inspection.
However, their low coverage makes them unsuitable for surveying large projects. Think about a highway, a railway track, a water retention basin or large infrastructure like an airport. It will take multiple flights and multiple days to survey the whole area. In one flight, WingtraOne can map almost 2x more than a conventional fixed-wing drone and approximately 10 to 15x more than multicopter drones.
“Our pilot in the field has a WingtraOne, a Phantom, Sirius and a Falcon, and if I told him ‘please go and get some measurements,’ every time he picks Wingtra.” said Vaiko Veeleid, CEO of Hades Geodeesia.
Even for sites that a normal multirotor can cover, a VTOL fixed-wing might be necessary. In some parts of the world you often have bad weather conditions. So as soon as the conditions are good you need to cover your site as quickly as possible. Having a drone that can get the data in a short time window is critical in these cases.
Vertical take-off and landing (VTOL)
Another advantage of WingtraOne is the vertical take-off and landing. “We looked at fixed-wing drones, but they need a passage to land, and we often have small places for landing. We can take off and land everywhere with WingtraOne. It’s really good,” explained Kjellsmoen, from the Norwegian Roads Administration.
WingtraOne offers fully-automated flight, it takes off from and lands in a predictable and tight space without requiring the operator to risk entering the construction site itself.
In this video we see the WingtraOne VTOL drone taking off and landing vertically like a helicopter and tilting to forward flight mode to fly like a fixed-wing aircraft.
Also, unlike drones that land on their belly, WingtraOne’s cameras never come into contact with the ground. This protects the high-quality sensors from abrasion, dust and dirt common to rough terrain found on construction sites.
Accuracy and high-resolution
Because an entire construction project will be based on geo-spatial data, it needs to be accurate. Equipped with the 42 MP full-frame Sony RX1R II camera and a multi-frequency PPK GNSS receiver, the WingtraOne delivers best-in-class GSD down to 0.7 cm/px (0.3 in)/px GSD and absolute horizontal accuracy, down to 1 cm (0.4 in). It can thus quickly generate detailed, high-resolution imagery on large areas, also enabling excellent accuracy around stockpile and earth volume calculations.
WingtraOne can map a 130 ha (320 ac) quarry in an hour’s flight. The resolution of the final map allows you to zoom in and see a coin lying on the ground. And what is best is that it’s possible to know the exact coordinates of the coin down to an absolute accuracy of 1 cm (0.4 in).
Easy operations
WingtraOne flights are fully automated and require no piloting skills and little training. The flight planning is done via WingtraPilot, an intuitive app with various ways to prepare flight plans, as well as monitor and revise missions during flight.
Atkins—a global consultancy firm and member of the SNC-Lavalin Group—has been developing design and engineering expertise around such infrastructure recently using WingtraOne to survey two stretches of sea wall defense. “The thing I found with the Wingtra is that it’s very straightforward to use, because of the way that it’s a complete system,” said James Fleming, Geomatics consultant at Atkins. “The software comes with the drone, and with the camera and the PPK integrated. You don’t need to measure any offsets yourself between the GPS and the camera.”
Corridor mapping
The corridor mapping feature enables fast, efficient coverage of long, narrow stretches. It proves especially useful for the following types of aerial mapping projects: roads and railway track construction and monitoring, pipeline and power line inspection, river mapping, etc.
This video demonstrates mapping of a 7.1 km (4.41 mi) stretch of road in Switzerland.
Standard format
WingtraOne’s images are standard and software-agnostic. This means you can process them with all major photogrammetry software out there. Further integrations, such as the one with Trimble Business Center, makes getting highly-accurate geospatial data to CAD or GIS software more seamless.
