Everyone benefits from roads and highways. From drivers going to work, truckers driving across the country, down to people waiting for their package by mail. The US spends over 50 Billion dollars every year on the maintenance and construction of new roads and highways, but that pales in comparison to China who is spending over 200 billion dollars per year and adding an average of 500 miles of highway per month.
It’s no surprise then that drones found themselves an essential role in the industry. Drones can work with a smaller crew and cover a lot more ground than the traditional method, saving a lot of money in labor.
Since drones can also fly faster and remain more accurate than traditional crews there is a major time saving as well, they can collect days worth of information in hours that only requires minimal revision.
Even small savings can add up to millions on these super projects, and minutes saved can equal months of time over a 5-year span, which likely means drones will only become more and more valuable in the infrastructure and construction industry.
There are three primary ways drones are being used in the construction of roads and highways. The simplest is also one of the most important, since drones can take high-quality pictures and fly hundreds of miles it makes them the perfect candidate for inspections. Crews can sit comfortably and watch a screen as the drone flies down the road looking for cracks or potholes, and operators can fly around bridges and other structures to see areas that are difficult to get to.
Land Survey and Planning is another place where drones have a huge advantage. Being able to gather data from high above using highly accurate GPS coordinates and other technology for future construction saves time, and drones can get to areas where ground crews can not. The maps generated are used in the planning of roads, as well as cost estimates and finding the optimal routes.
Lastly, once construction begins drones can be used to take pictures and compile reports, tracking progress over time and updating crews with real-time information. This can include tracking the amount of material used and remaining. Drones can be used in roadway construction by inspecting, surveying and tracking progression.
The Benefit of Using Drones in Construction
A ground crew in a truck has to stop and set up regular points and intervals to do surveys that a single drone can do in one flight. Aerial photos that used to be gathered by plane or helicopter can instead be taken by drones, reducing the hours of preparing for flight, taking off, and landing. Transferring the photos and data from the drone is easier done at the job site than from a plane or helicopter.
The software that drones are utilizing allows them to gather the data and turn it into usable information instantly, rather than having to be pushed through teams that interpret and compile it. At almost every step of the way, drones can save time, including some more abstract ways outside of their speedy data collection.
By flying a drone for inspection or progress reporting you can spot problems that would otherwise go unnoticed and plan to solve them before they develop into major issues.
The ability to foresee any problem is a major part of any construction project since mistakes and minor setbacks are the biggest time consumers, a company could shave months off of a single project simply by knowing ahead of time where a problem is going to occur.
Drones have a major advantage over small survey crews when it comes to accuracy. First, using drones can offer real-time information. You don’t have to rely on a map made years ago, or survey maps made decades ago. You simply fly the drone on-site and are able to work with current data.
Second, drones can cover huge distances with a very high level of relative accuracy. Unlike a crew that will have to survey in small sections and then place all the sections together over time, the drone can make a map of the entire project all at once eliminating the possibility of human error in measurement or stitching.
This is especially true for topological data, where a team might work all day with equipment in order to build 50 data points where a drone can gather thousands in a single flight. Since each data point represents a point in 3d space the more you have the more accurate your map is.
Sophisticated software can even remove trees and features from a survey map, which means you can accurately plan dirt work and pathing without worrying about the flora and other features causing inaccuracies with a traditional land survey.
A traditional survey crew traditionally consists of 5 or more individuals. They use trucks, lasers, tripods, receivers, and a variety of computers and programs stretched out over months. 2 operators and a single drone can do the same work, meaning that the other personnel and equipment are free to do other things.
Since drones and drone software often run on small devices like smartphones or portable tablets you don’t need access to an office to compile the data, and sharing the data becomes as simple as dragging and dropping the file to whoever needs it.
What Is Required?
To use drones in this capacity you really only need 2 things: A drone to capture the data and software to compile that data into usable information. Sometimes you will need highly accurate GPS receivers for the creation of ground control points as a reference. There are a lot of different factors that come into play depending on what you need. See below for the basics of all the different options one has when getting into such an endeavor.
Fixed Wing, Multirotor Or Hybrid?
Drones come in a variety of shapes and styles allowing you to choose the drone that’s right for the job you want to do. There are three general categories of drone: Fixed Wing, Rotorcraft (Multirotor), and Hybrid. Which one is best for the job largely depends on the scale of work needed to be done.
Fixed wing UAVs can fly long distances, often much faster than their multirotor counterparts. Drones using fixed wings are often purpose-built for mapping and surveying.
The Parrot Group has a drone called the Ebee, a single motor fixed wing craft that can create a map of 4.6 square miles on a single charge. Larger industrial drones, like those used by the government, military and geological survey companies, can fly for days and store terabytes of data on built-in hard drives.
Pros of Fixed Wing UAVs include long flight times, very fast flight speeds, and the ability to use minimal input to stay on course freeing up memory and processing power for other operations.
Cons of Fixed Wing UAVs include cost, ranging from a few times more expensive than rotorcraft in the case of the Ebee to thousands of times more expensive in the case of the industrial UAVs, and space requirements. Not only are Fixed Wings physically larger than their rotorcraft counterparts, but they also need runways to take off and land. They are also not able to hover and inspect a specific area.
Multirotor drones are more common and found everywhere. Since there are many manufacturers that make them there are a lot of options, with many manufacturers offering packages to transform existing consumer drones into a dedicated mapping platform.
The DJI Phantom RTK is based on one of the most popular drones on the market, the DJI Phantom, and comes equipped with highly accurate GPS modules and sensors that interact directly with ground stations.
Pros of Multirotor UAVs include transportability, ease of use and cheaper costs. Especially since you can go to stores and buy parts for many of the drones used, the cost of maintenance is also greatly reduced.
Cons of Multirotor UAVs are mostly related to battery life. Having to run 4 or more motors severely limits the amount of time it can be in the air. Because they need more energy just to stay in the sky payloads become more limited and speed diminishes in favor of efficiency. This also means Multirotors are unable to cover as much ground as a fixed wing.
Although uncommon at this time, there are drones that combine the efficiency of a fixed wing with the ability of a multirotor to take off and remain stable in the air. The Wingtra One is a drone that takes off like a helicopter but flies like an airplane, maximizing endurance and payload capacity without sacrificing the ability to take off and land in a small space.
Pros of a Hybrid or Vtol UAV include the ability to fly long distances like a fixed wing, but still require little space for operation like a multirotor.
Cons of a Hybrid or Vtol UAV include the fact that they are somewhat rare, not many manufacturers are building them which means they tend to cost more, and they suffer from the problem that any hybrid system has. Since they need to balance stability and endurance, it is difficult for them to currently match up to a dedicated rotorcraft or fixed wing.
Camera vs LIDAR
When surveying and mapping there are two main sensors used. Normal cameras and LIDAR. While most drones come pre-equipped with cameras, there are advantages to using a LIDAR sensor instead despite the added cost and complexity.
Photogrammetry Using A Standard Camera
Photogrammetry is the process of taking a lot of pictures and stitching them together into a single map. It is highly accurate (when done correctly a good map is accurate to within centimeters) and provides great visual data.
Since these maps are made of high resolution photos, it’s easy to zoom in and see individual details and landmarks. Making a photomosaic useful beyond survey and mapping purposes. Since most drones are already equipped with cameras, this is the most common form of land surveying and mapping.
LIDAR, or Light Detection and Ranging, uses lasers to measure exact distances. Unlike Photogrammy which needs many pictures from different angles to create a map, a LIDAR unit can sweep an entire area in one pass, saving a lot of time.
The maps created by LIDAR are also highly accurate and can be even better than a photomosaic map. They have the ability to “see through” dense trees and obstacles making LIDAR invaluable for mapping forests.
LIDAR can also see things that a standard camera can not, since lasers will reflect off of any surface the detail is near infinite. Even a 20mp image does not have the resolution to show power lines or fence wire, both will be captured accurately using LIDAR.
However, LIDAR units are incredibly expensive. The cost can get up to $20,000 USD or more for just the drone-mounted sensor. The complete systems can reach $100k.
These systems require many components compared to a simple camera. They are also much bigger and heavier than a standard camera, severely limiting their application. Unless you are mapping very large areas or areas with a lot of obstacles that need ultra-high detail, the complexity and cost of LIDAR is not worth it.
Drone Mapping Software is primarily responsible for 2 things: Automating the drone for capturing the map, and compiling the map into accurate usable information. Most drone mapping software is capable of making photogrammy maps from pictures in real time as well.
DroneDeploy, Precision Mapper, Maps Made Easy, and Pix4d are some of the leaders in drone mapping software, each with their own strengths and weaknesses. Maps Made Easy and Precision Mapper are only for mapping and stitching the pictures together. They rely on you obtaining the pictures separately and uploading them into the software.
Others, like Pix4d and DroneDeploy, have their own mapping tools that fully automate the image capture process. There are also apps and software that work in conjunction with the primary mapping software.
Litchi is a flight path tool that can be used to make complicated flight paths and maps that require special flight parameters, while Propeller is software that aids in analyzing the maps and turning out highly useful information including area calculations, volume calculations and has tools specifically related to construction.
GCP, RTK & PPK
In order to fully utilize the software, three terms get thrown around a lot when discussing mapping and surveying with drones, GCP, RTK and PPK. These are the main methods for ensuring accuracy on a drone map. The GPS on your drone is good, but not amazing, so we use these technologies to correct the inaccuracies created.
Ground Control Points (GCPs)
Ground Control Points are the simplest to understand. Simply put, they are points on the ground that you are 100% sure of the coordinates. A surveyor places markers on the ground that represent those points and when the drone captures the images for the map, those markers appear in the map and can be assigned their exact location using the software.
It takes a lot of prep work, but using GCPs can not only make a map accurate to within millimeters but also overlay it accurately on larger geographical maps. The use of Ground Control Points is slowly being replaced by GPS Correction, which is a much faster process and still produces amazing accuracy.
Real-Time Kinematic (RTK) and Post Processing Kinematic (PPK)
RTK and PPK are both technologies used for GPS correction. The primary difference between the two is that RTK, as its name implies, happens as the data is being collected while PPK happens while the data is being processed.
RTK uses the drones sensors and software to correct the map as the images are being taken by checking it against known points. A home station constantly checks on the drone to calibrate the GPS and other information, while the software makes small changes to the output. The end result is a map that needs little post-processing.
However because the RTK drone needs constant connection to satellites and the home station, the process has a disadvantage that can cause inaccurate data. If any connection is lost or calibrated incorrectly the information will simply be lost and must be taken again.
PPK does not need the drone to be connected to any system. PPK uses information stored on a cloud or on large servers to cross check the maps after they are already made, and software makes the corrections during rendering rather than real time. This means that using PPK requires less equipment and has a much lower chance of failure, however, you do sacrifice the speed and ability to update the data in real-time.
How Drones are Used for Road and Highway Work
Using Drones for Roadway Inspections
Now that we have a good idea of how drones survey and the different options available, let’s look deeper into applying this technology to help Road and Highway work. Roads deteriorate over time, bridges develop cracks and highways begin to lose integrity as the layers break apart.
Drones can easily fly along the roads and provide thousands of inspection photos, mapping entire roadways in a very short amount of time. An operator can then review those pictures over time in an office rather than needing to physically drive the roads.
They can then send the drone to specific areas to capture high-resolution images of problems in order to follow up and make detailed reports of the issue. Since drones are so easy to automate, an operator can save routes and run the same routes monthly for scheduled inspections without having to worry about crew availability or scheduling conflicts. Saved routes are an effective way to track progression of deterioration or construction.
For bridges and other structures, drones can inspect all the areas that are difficult for humans to get to. While the bottom of a support pillar may be in a remote, difficult to travel to location it’s not a problem for a drone to fly down and take pictures or video, even close to water or near other obstacles.
Dirt roads and other more difficult to transverse regions are also not an issue for a drone. While a construction area might have muddy, nearly impassable roads that would make it difficult for an inspector to see hillsides and other road engineering features, it is simple to send a drone team in to manually take pictures and report real time findings.
Surveying and Planning
Since drones can make maps that cover very large areas that are accurate, their use in surveying is invaluable. The detailed maps can be used in every aspect of planning and construction, from laying out the path a road will take to calculating the amount of material needed for a given project.
When planning a route it’s important to find the best compromise between having the shortest path and avoiding obstacles. The only way to do that is to be able to see the entire area. Before drones, planners would use old topographical maps and new survey maps to make their best guess at current conditions. With drones they are getting the most current information possible and at higher levels of accuracy than previously possible.
The maps can be put directly into plans and calculations as well. With 3D mapping calculating things like required fill dirt and dirt movement. Other materials needed like concrete and rebar is simply a matter of highlighting an area and clicking calculate. Area, Distance and Volume become trivial to find, and maps can be sent directly to engineers and drafters in order to make planning and development easier.
This is especially useful when making improvements to existing roads and structures, taking the guesswork out of reading old plans completely.
Progress Reports and Supervision
Once construction is started it is incredibly important to keep track of progress and constantly update plans. With programmed flight paths and regular schedules, a drone can fly an entire construction site, take pictures, return home, offload the data, and repeat the next day. The progress maps can be used to highlight potential problems, redo calculations in the event of changes and instantly update inspectors and supervisors.
Having these records can also come in handy for settling any disputes between planners and contractors, or keeping records for permit and bureaucracy reasons. It also makes an excellent monitoring tool for keeping track of inventory. If you need to know how many blocks are on site or how many tractors are available, you simply bring up the days map and count.
Almost all Survey and Mapping work is commercial, so any operator will need their Part 107 Certification. Maps that are large enough to require flying beyond line of sight will require the 107.31 waiver, and some advanced drones will require the 107.51 waiver which makes allowances for speed, visibility and altitude.
Currently the FAA is working with manufacturers to include Remote ID capability on drones. The proposed new rules will allow people to use receivers to identify the owner and position of any drone. Drones with remote IDs may be able to fly without waivers, but the proposal has not yet finished being written.
Drones are rapidly becoming invaluable tools all across the construction industry. Due to the large geographic areas and massive scale of the projects, the road and highway construction industry can greatly benefit from the properties of drones, saving huge amounts of time and money while providing greater accuracy and planning capabilities.
Between fixed wing UAVs flying hundreds of miles at a time and consumer drones creating real-time reports, you can expect to start seeing drones everywhere you find the orange vested road crews.