OSDC is using UAV surveying techniques such as Photogrammetry and LiDAR in a big way on heavy civil sites construction sites throughout BC. As construction projects become more complex, rapid and precise data capture and analysis are essential to successful project completion. Drone aerial mapping provides near real time data allowing clients to rapid make informed decisions on the fly that drive productivity, efficiency and profits like never seen before. Drone imagery and video on construction sites is also a reliable solution for documenting the progress of these large-scale projects from start to finish via volumetric and progress surveying, ensuring contractors are getting paid for every bit of material they have moved.
By leveraging this technology, field level workers, engineers and senior executives can streamline processes, ensuring accuracy in each stage of development and gain valuable insight into potential issues before they arise. In this article, we’ll provide an overview of drone aerial mapping processes, and discuss important planning considerations when utilizing drone technology for volumetric reporting and generating critical real time site surface model information. This information will ensure that heavy civil sites are being run as efficiently as possible, with the ability to make informed decisions that drive productivity, efficiency and profits like never before.
Image of a 3D model generated using drone Photogrammetry survey techniques and ground control points from a construction survey flown on a large gravel pit near Vernon, BC. Note the level of detail is so dense the windrows left behind from a bulldozer forwarding the material is visible.
Our team of highly trained professionals provides the perfect formula for success on large site grading and earth moving projects. Combining a proven roadmap with specialized survey technicians, Transport Canada certified drone operators and an experienced design team boasting over 60 years of combined onsite construction and project management insight ensures that material is always moved strategically, economically and efficiently. Using drone technology to its full potential can save you hundreds of thousands in waste and rework to keep your construction project ahead schedule!
At OSDC we put a massive amount of work in at the planning stage to ensure we maintain an extremely high standard of safety, communication, reliability, and precision.
We are committed to maintaining the highest level of safety of all construction site workers and bystanders. We implement a robust contingency plan for any potential drone issues so we know what could go wrong and have a plan in place in the event it does, which is highly unlikely when UAV missions are planned properly. To ensure proactive risk management, we alert all personnel about the upcoming use of drones and associated risks, such as possible malfunctions that could cause fire or runaways.
Drone launch and landing area
As Transport Canada Advanced Drone Operators, we are required to always maintain visual line of sight (VLOS) on the drone, meaning it always must be in eye shot of us. The first thing we do when arriving onsite is do a site survey looking at things such as site features, people, the topography, and tree and vegetation cover that will impact the mapping mission. We then decide if the mission can be completed from one vantage point, or if we will have to use multiple launch/landing areas. Ideally, we will be able to cover the entire site from one spot but that’s not always possible. The launch and landing area is intentionally planned to be away from equipment, people and other noises that may distract our drone pilots while the aerial mapping mission is being conducted.
Flight planning and coordination
Aerial surveying requires careful consideration of multiple elements. Before commencing any flight operations, operators must be aware of the airspace class they’re navigating in addition to any nearby Aerodromes or airport authorities that are required to be notified prior to the mapping survey. It’s also essential to check for Notice To Airmen (NOTAMs) for events such as forest fires and weather-based events, as well as checking weather predictions including humidity, wind speed, direction and atmospheric pressure. This information is used in gauging favorable conditions prior to takeoff. When we are planning our flight paths always aim for an optimal 75 – 80% front and side overlap rate. This will enable us to generate more precise positioning data ensuring at least three images contain the same features which is essential for proper drone Photogrammetry processing. With a keen eye on these small details drone flying becomes a safe and successful adventure every time!
Terrain topography and features
The topography of the site and being aware of features within the area of interest is one of the most important considerations for determining the height above ground level (AGL) for the flight. Too high and we get poor quality data, too low and we risk crashing into features such as trees, buildings, etc. A lot of consideration goes into our drone pilots calculating a suitable AGL height as changing the height is a balancing act. We adjust the height to improve one thing but that inevitably negatively effects another. Different flight planning software has different control features for controlling the drone’s altitude. Some software will use a specific height above ground level (AGL) from your home base or drone take-off and landing area, i.e. It will hold a specified Geodetic height. Others will hold a specified height above ground level by following the topography of the land below the drone, this is referred to as “Terrain following”. In areas with undulating and steep terrain like Kelowna, Vernon, Prince Rupert and Kitimat, British Columbia we have had great success using terrain following techniques.
Prior to a drone mapping mission our technicians and pilots will always check critical drone components. Things like battery capacity (using a digital multi meter) to rule out false readings on battery indicators, checking the drone for structural damage, checking the propellers, ensuring the camera gimbal is operating properly, and checking for firmware updates are all part of the pre-flight inspection. Additionally, they will ensure the appropriate parties have been notified for the class of airspace we are flying within, check radio latency, and proper programming of the home base so that in the event of a flyaway, loss of radio link or battery power depletion the drone will safely return home
The scope of work and objective
The first thing we stress to our operators is the importance of understanding the reason they are conducting their work. Only when we understand the why important decisions around precision, resolution and quality become clear. As mentioned above calculating the ideal height above ground level (AGL) is one of the most critical factors in flight planning. Drone resolution is measured in Ground Sample Distance (GSD). GSD is a key limiting factor and calculation in the precision and resolution of your drone mapping data. GSD can most easily be defined as the distance between the centre of two consecutive pixels in the drone imagery. The higher the GSD the lower the accuracy and conversely, the lower the GSD the better the quality. The two primary factors that determine GSD are the photo quality of the camera and the flight altitude. Both must be accounted for when planning an aerial mapping survey. Having a higher resolution camera will allow the drone to be flown at a higher altitude significantly reducing flight time whilst maintaining a very high level of accuracy. Another key consideration when planning a drone mapping survey is the flight speed. Again, there is a sweet spot here as the faster we fly, the lower the quality but the quick the completion of the project, and with a smaller data set resulting in faster processing and turnaround times to our heavy civil construction clients. These factors heavily influence the end data result and are the reason why understanding the survey objective at the project start is critical.
Deciding on the most appropriate sensor (Photogrammetry or LiDAR)
Drones and photogrammetry have become increasingly popular tools for construction projects. This technology offers a new way to survey, monitor, and inspect construction sites quickly and cost-effectively. A skilled UAV mapping surveyor will know the best approaches in deciding the best tool for the job at hand. In short, we use LiDAR to collect original ground topographic survey data as we can measure the bare earth through tree canopy and vegetation, and Photogrammetry of a site once clearing and grubbing is completed.
Below is a brief introduction to the two sensors we most common used on construction sites
Drone photogrammetry is the process of creating three-dimensional models from digital aerial images captured by unmanned aerial vehicles (UAVs). The UAVs take pictures from all angles, which are then processed with computer software to create an accurate 3D model. This model can be used to measure distances, calculate volume, analyze shapes, and determine elevation changes. There are many ways that drone photogrammetry can be used in construction projects. For example, it can be used to survey large areas quickly and accurately. It also helps with progress monitoring by providing detailed data about the project site over time. Additionally, it can be used to identify potential safety hazards or other issues that need attention before they become more serious problems down the line. Finally, it can be used to create highly detailed maps of the project site that can be shared with stakeholders in different formats depending on their needs (e.g., PDFs or interactive 3D models). Using drone photogrammetry offers several benefits over traditional surveying methods. It is faster than manual surveying; it takes less time to process data; it is more accurate; and it provides high-resolution images that allow for greater detail when analyzing data points such as elevation changes or distances between objects. Additionally, because drones are lightweight and easy to use, they require less manpower than traditional surveying methods—saving both time and money in the long run. Drone photogrammetry has revolutionized the way we survey construction projects. With its speed, accuracy, and cost-effectiveness, this technology allows us to get more done in less time while ensuring a higher level of quality control throughout the project lifecycle—from preconstruction planning to postconstruction documentation. Whether you’re a CEO looking for an efficient way to monitor progress or a foreman wanting detailed maps of your job site, drone photogrammetry has something for everyone involved in construction projects!
Model of a heavy civil construction project on a landfill flown in Kelowna, BC using photogrammetry techniques. Note the level of detail is so dense that we can pick out the tread pattern of the rock truck tires and even vertices in the pile of rock.
LiDAR (Light Detection and Ranging) is a surveying technique that uses laser pulses to measure the distance between objects. It has become increasingly popular in the surveying and mapping field, as its accuracy and efficiency provide many benefits to the heavy civil and construction sector. The combination of LiDAR’s accuracy and ability to measure bare earth through tree canopy and vegetation coupled with the drone’s mobility allows for remote surveying in difficult-to-access areas, such as rivers, mountains or dense forested areas, as well as high-risk-access areas such as mining or heavy civil construction sites a breeze. Drones are also able to fly at lower altitudes compared to traditional aircrafts for more precise results and significantly lower costs and deployment times. This makes it easier for surveyors to rapidly capture accurate topographic data on large areas of land with steep dangerous terrain, trees and vegetation without the need for expensive equipment or complicated setup procedures. Furthermore, using drones equipped with LiDAR allows surveyors to collect data quickly and easily while reducing costs significantly compared to traditional methods. The entire process can be automated and requires less manpower than manual surveying operations, making it more efficient overall. Additionally, because this technology is non-invasive and does not require any contact with the ground surface, it also reduces safety concerns associated with manual surveys that involve physical interaction between personnel and terrain. When combined with GIS (Geographic Information System) software, the data collected by LiDAR drones can be used for detailed analysis that would otherwise be impossible using conventional methods. This includes 3D modeling of terrain features, volumetric measurements of stockpiles, area measurements of construction sites or vegetation assessments in forestry applications. All these types of analysis can be performed quickly and accurately thanks to the high precision provided by LiDAR drones compared to traditional methods.
Sample of a Bare Earth Model generated from our UAV LiDAR. The site was sparsely treed and vegetated. Conventional survey would have taken approximately 3-4 days versus the 4 hours required using a UAV.
Ground Control Points (GCPs)
In order to ensure drone data is georeferenced, meaning it is spatially correct and in a desired coordinate system, vertical datum and scale a qualified survey technician must set Ground Control Points (GCPs). Ground Control points are markers (typically a spike or nail) set in the ground that will be visible in the drone mapping imagery. We will use Global Positioning Systems (GPS) to establish precise coordinates on these points. These points will then be used to process the data and transform the drone mapping data set to align to the GCPs precise known coordinates. In short, the Ground Control Points ensure the northing, easting and elevation of the output map align with real world coordinates. This is extremely important while conducting progress and volumetrics surveys on large heavy civil construction sites where we will be taking many data sets over the course of construction. If the drone data mapping is not collected or processed correctly the resulting outputs will be incorrect resulting in massive amounts of volumetric error. When placing Ground Control Points (GCPs):
- We start by setting points just outside of the area of interest. These act like the legs on a table, so we want GCPs at all major corners or deflection just outside of the scope of work
- Next, we will set GCPs within the project boundary to prevent “doming” on the digital surface model
- Finally, we will set points at major high and low points in the topography.
As a minimum we will set 6 Ground Control Points in addition to the check points we record on all aerial survey projects.
Quality assurance and validation surveys.
Drone mapping technology has the potential to transform levels of efficiency, eliminate waste and increase productivity in a massive way but, if done incorrectly, also has the potential to cost hundreds of thousands of dollars in underpayment, overpayment, tarnished reputation, and re-work. Having processes in place to eliminate and catch erroneous data is critical and often overlooked. A few systems OSDC uses to validate our surveys include:
- Our GPS survey crew take a certain amount of “check shots” on the project
- We have developed and implemented Standard Operating Procedures (SOPs) for all functions at OSDC including our construction site drone sector
- OSDC has a solid network of people to review data sets and field procedures offering multiple points of feedback and redundancy.
- We put a lot of effort in at the planning stage – as with anything, proper planning, communication and redundancy (the ‘measure twice, cut once’ principle) is the strongest form of eliminating error.
As construction projects become more complex, the need for rapid and reliable data capture, jobsite target and analysis has increased dramatically. Getting one thing wrong can make the difference between profitability or a loss. Drone aerial mapping provides a solution for reporting on and documenting these large-scale projects from start to finish and offer invaluable information for making real time critical decisions around jobsite optimization, volumetric surveys for balancing cuts and fills and tracking progress for volumes. This technology can be utilized by field level workers, engineers and senior executives to collaborate remotely, streamline processes, and ensure accuracy at each stage of development and construction while gaining valuable insight into potential issues before they arise. Hiring OSDC is the industries turnkey solution for heavy civil contractors that are wanting to rapidly make a massive technology transformation without missing a beat and running at unheard of levels of profit and productivity. If you would like help incorporating drone aerial mapping into your business procedures, please contact us on firstname.lastname@example.org, we would be happy to discuss your specific requirements and how we could assist you.