In today’s rapidly evolving world of technology, drone-based volumetric surveys have emerged as a highly accurate alternative to traditional methods. There are many advantages to utilizing unmanned aerial vehicles (UAVs). Equipped with advanced sensors and software to provide precise measurements of stockpiles, landfills, and natural resources, drones can create highly accurate volumetric surveys.
Using drones to calculate stockpile measurements makes it easy to compare your current stockpile volumes to previous surveys and track site progress. You can also compare stockpile surveys to a final grade design file to calculate how much material you still need to add or remove.
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This article examines drone technologies that ensure accuracy, such as RTK GPS and GCPs, and compares the photogrammetry and LiDAR methods used to survey stockpiles. By uncovering the potential of drone-based volumetric surveys, this article aims to inspire informed decision-making for mining, aggregate, and general contractors.
What are Drone Volumetric Surveys?
Drone-based volumetric surveys refer to the use of drones equipped with specialized sensors and software to accurately measure the volume and quantity of materials such as stockpiles, landfills, construction sites, or other natural resources. The surveys involve capturing high-resolution aerial imagery or LiDAR datasets to generate 3D models, allowing for precise volumetric calculations.
What's included in YOUR GUIDE...
A Proven Roadmap of Success for Implementing Drones in Construction.
A List of Red Flags to Avoid When Hiring Drone Service Providers.
How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
Advantages of Drones for Precise Stockpile Surveys
- Accuracy: Drone-based surveys offer a high level of accuracy in measuring volumes, providing reliable data for various industries, including mining, construction, agriculture, and environmental monitoring.
- Efficiency: Drones can rapidly cover large areas in a short time, significantly reducing the time and effort required for surveys.
- Safety: By eliminating the need for personnel to climb or traverse hazardous terrains, drone surveys enhance safety on job sites and reduce the risk of accidents.
- Cost-effectiveness: The use of drones can lead to cost savings as they require fewer resources and personnel than conventional methods.
- Data Visualization: The 3D models generated offer visual representations of stockpiles and landscapes, aiding in better understanding and decision-making.
- Monitoring and Analysis: Regular drone-based surveys enable the tracking of changes over time, facilitating ongoing monitoring and analysis of stockpile volumes or environmental conditions.
GNSS Receiver & Survey Bipod Capturing Ground Control Points
Technologies & Strategies Enabling Accuracy
RTK GPS and Ground Control Points (GCPs) for Improved Precision
Two key technologies play a vital role in achieving survey precision; Real-Time Kinematic (RTK) GPS and Ground Control Points (GCPs). RTK GPS ensures real-time centimeter-level accuracy by providing precise positioning information to the drone during flight. This technology minimizes positional errors, resulting in highly accurate data used in volumetric calculations.
GCPs, used in conjunction with RTK GPS, are strategically placed markers on the ground with precisely known georeferenced coordinates and can be captured with a GNSS Receiver Rover. These points act as reference markers, allowing the drone’s imagery and data to be accurately aligned with the Earth’s coordinate system. By integrating GCPs into the surveying process, errors arising from drone positioning and camera calibration are mitigated.
Incorporating checkpoints is also an important step in validating accuracy of the survey. Checkpoints work in a similar way to how GCPs are laid out, but they are processed by the software in a different way. After completing the survey, these checkpoints are used to calculate map errors and will verify the accuracy of the data generated. This validation process instills confidence in the accuracy of the volumetric calculations, providing clients with reliable data for decision-making and project management.
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Volumetric Software Settings and Parameters
It is essential to note that ensuring accuracy goes beyond the use of RTK, GCP, or checkpoint technology alone. The software employed for processing drone data is a pivotal component in the accuracy of volumetric surveys. It serves as the digital canvas where intricate calculations and measurements are made to generate proper analysis of the data collected. One key aspect within this software framework is the selection of the correct baseplane, a crucial setting that profoundly impacts the precision of recorded measurements. The baseplane essentially establishes the reference point from which all volumetric calculations are derived, making it indispensable for ensuring the utmost accuracy in the final results.
Drone Stockpile Processing via DroneDeploy
Analyzing Material Condition & Properties
Furthermore, achieving precise volumetric readings is not solely dependent on sophisticated software; it’s also contingent on inputting critical parameters into the system. Details such as the type of material being surveyed, its density, and even its current condition (whether it’s wet, dry, loose or compacted) play a vital role in refining the accuracy of the survey. This input not only customizes the calculations but also allows the software to account for material-specific variations, ensuring that the volumetric measurements align with the real-world characteristics of the stockpile. Therefore, meticulous attention to these details and their integration into the software is paramount for achieving the most accurate volumetric readings in drone-based surveys.
In addition to the critical role of software and data input, drones exhibit remarkable flexibility when it comes to surveying various stockpile scenarios and conditions. They are capable of effectively surveying stockpiles located up against walls or instances where two stockpiles are tightly positioned next to each other. Unlike traditional surveying methods that may struggle in confined or obstructed spaces, drones excel in these scenarios. Their agility and ability to capture data from multiple angles allow for comprehensive coverage, ensuring no detail is missed, even in complex stockpile configurations. This adaptability makes drone-based volumetric surveys a preferred choice for industries where stockpiles can vary significantly in size, shape, or placement.
Comparing Surveying Methods: Photogrammetry vs. LiDAR
Photogrammetry: 3D Models from Images, Advantages, and Limitations.
Photogrammetry, the more common method for drone-based volumetric surveys, involves capturing a series of overlapping aerial images using the drone’s camera. These images are then meticulously processed with specialized software to construct highly detailed 2D or 3D models of the surveyed area. The cost-effectiveness and simplicity of employing a camera-equipped drone make photogrammetry an attractive choice, particularly for expansive surveys that demand efficient coverage in a single flight.
However, it’s important to note that photogrammetry has its limitations. The quality and precision of the resulting models are contingent on factors such as image acquisition height, camera resolution, and high image overlap. Additionally, challenging environmental conditions like inadequate lighting or complex terrain, including obstructions like trees or roof structures that hinder a direct overhead view of the stockpiles, can affect the accuracy of the outcomes. Nevertheless, despite these constraints, photogrammetry continues to be a valuable method for volumetric surveys, particularly when budget constraints and accessibility are integral to the decision-making process.
Stockpile Drone Survey Using Photogrammetry
LiDAR – Uses and Comparison with Photogrammetry.
LiDAR (Light Detection and Ranging) is an alternative surveying method that utilizes laser sensors to measure distances between the drone and the surveyed objects or surfaces. By emitting laser pulses and measuring the time it takes for the pulses to return, LiDAR systems create highly accurate 3D point cloud models. This technology excels in capturing detailed elevation data, making it ideal for applications where precise height measurements are crucial, such as with volumetric surveys and analysis.
Compared to photogrammetry, LiDAR has some distinct advantages. It is less affected by lighting conditions, making it suitable for surveys in lower-light or even nighttime environments, and it can penetrate vegetation, important for surveying vegetation-covered areas. LiDAR does have some challenges to overcome as well. LiDAR can be more expensive and complex to implement compared to photogrammetry, and it can generate large data sets leading to higher data storage and processing demands.
An experienced drone service provider can help you make the choice between photogrammetry and LiDAR. This often depends on the specific project requirements, budget constraints, the level of accuracy needed for the survey, and the expertise of the drone pilots.
Stockpile Drone Survey Using LiDAR
Accuracy Standards of Drone Volumetric Surveys
A recent comparative study was completed between drone technology vs traditional survey methods to determine the accuracy of volumetric stockpile data. After an extremely detailed approach to the study, the drone percentage error to the actual stockpile volume was determined to be 2.6%, which is less than the maximum allowable percentage error of ± 3.
Compared to the traditional approach drone technology provides an accurate, cost-effective, fast, and safe working distance suitable for stockpile volumetric computations.
Photogrammetry can achieve horizontal (x-y) accuracies in the range of 1 cm (0.4 in) and elevation (z) accuracies of 2 to 3 cm (0.8 to 1.2 in) over hard surfaces when utilizing a quality, high-resolution, full-frame sensor camera like the Sony RX1R II on a commercial drone. However, it’s essential to note that achieving such performance hinges on the use of a professional payload with the right image sensor and lens to capture intricate details. The image sensor’s size plays a crucial role in image quality and survey accuracy.
LiDAR, on the other hand, provides an alternative route to accuracy. Lightweight drone LiDAR systems can cover substantial areas per flight, sometimes exceeding what manned aircraft can achieve. Some commercial drones equipped with LiDAR payloads can cover up to 10 square km (4 square miles) in a single flight, with absolute accuracy limits around 10 cm (4 in) horizontally (x-y) and 5 cm (2 in) vertically (z). However, it’s important to emphasize that while LiDAR provides remarkable accuracy, its post-processing demands expertise and experience in the post-processing field.
Comparing photogrammetry and LiDAR drone surveys to the true volume of stockpiles is a nuanced process. Both methods can achieve a high level of accuracy, but the final precision often depends on factors such as equipment, terrain, environmental conditions, budget, and the experience of the drone service provider. Additionally, accurate volumetric measurements involve proper ground control and validation, such as the use of Ground Control Points (GCPs) and checkpoints, to ensure the survey results align with real-world values. Therefore, the choice between photogrammetry and LiDAR should be made according to the specific needs of each project, with careful attention to the accuracy required and the expertise available for data processing and analysis.
Getting Started with Aerial Volumetric Surveys
Drone-based volumetric surveys have revolutionized industries by offering accurate and efficient measurement solutions for stockpiles, landfills, and natural resources. Utilizing RTK GPS and GCPs ensures unparalleled accuracy, while checkpoints validate data reliability.
Photogrammetry provides a cost-effective and accessible option, ideal for large-scale surveys, despite some limitations in image quality and environmental conditions. In contrast, LiDAR excels in capturing detailed elevation data and penetrating dense vegetation, making it suitable for critical infrastructure assessments. Embracing this transformative technology paves the way for data-driven insights for aggregate facilities, earthworks contractors, and mining companies.
When considering drone technology applications for construction projects, it is highly recommended to hire a drone service provider with experience in this field. The Drone Life pilots, for example, are highly trained and qualified to conduct flights using all the methods outlined in this article. By hiring an experienced drone service provider, you can ensure that the inspections are carried out by professionals who understand the nuances and complexities of your project. Schedule a free consultation today with The Drone Life for more information.
What's included in YOUR GUIDE...
A Proven Roadmap of Success for Implementing Drones in Construction.
A List of Red Flags to Avoid When Hiring Drone Service Providers.
How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
