Quick answer: How are drones used to measure stockpiles?
With georeferenced images taken from a drone flying above your worksite, you can use photogrammetry to generate a 3D visualization of your site with measurements accurate to 1/10ft (3cm).
Leveraging that level of accuracy, you can use a drone survey visualization platform to take a variety of measurements, including stockpile volumes.
Using these tools, you can compare your current stockpile volumes to previous surveys to judge progress over time, or compare it to a final grade design file to calculate how much material you have left to add.
Using drones to measure stockpiles is fast becoming a go-to earthwork surveying workflow for sites around the world.
For professionals in the mining and aggregates industries, stockpile inventory management is one of the primary use cases for drone surveying. Similarly, construction sites are using drones to more quickly survey their sites and using the 3D maps generated from those flights to collect actionable data, including stockpile volumes.
By flying a drone to measure stockpiles instead of sending someone out to traverse a dangerous site, site management can track their inventories and site progress in a faster, safer, more reliable way.
Below, we break down how drones and photogrammetry are helping worksites improve stockpile measurement workflows and streamline site analysis.
- Why accurate stockpile volume measurements matter
- Using drones to measure stockpiles: the basics
- How to report on your stockpile volume measurements
- 3D blast planning and other drone surveying use cases for quarries and mines
Why accurate stockpile volume measurements matter
Mine and quarry managers spend much of their days trying to answer questions about quantities. How much is sitting in the stockyard right now? How much is going in the crusher or mill? What do you still need to extract? How much have you moved off site since last Thursday? What was its true value and did you sell it for the right price?
Having accurate site surveys at your fingertips—and thus full oversight of your stockpile inventory—finding the answers you need becomes a whole lot simpler.
Using a drone surveying workflow, you can count on dependable, highly accurate stockpile measurements. And you can measure progress as frequently as you want to fly. This influx of stockpile inventory data enables teams to tighten up worksite operations. That can include everything from financial forecasting and supply-chain management to accurate reconciliation.
1. Prepare more accurate financial forecasts
Using drones to measure stockpiles is cheaper and easier than using traditional surveying equipment. It’s also far more accurate than “eyeballing” stockpile volumes. They put the power of frequent surveying in your hands and accurate stockpile volume data at your fingertips.
Having accurate inventory numbers every month means drastically reducing future write-offs. This saves everyone on site money and boosts mine or quarry efficiency. Using drone surveying, “fluff factors” in inventory management have become a thing of the past.
And with recent developments in photogrammetry, smart ground control points (AeroPoints), and drone hardware, you’re able to generate models of your site with an accuracy tolerance of 1/10ft (3cm). That’s good enough for nearly anyone’s stockpile measurement standards.
2. Tighten up your supply chain
Knowing what you actually have on site also allows you to organize your supply chain better. Stockpile reports supply quick asset snapshots, from when you need more stock to how much you still need to extract. If you’re your own supplier, easily plan out when you need to start drilling and blasting based on current volumes. If you use an external supplier, you can plan out purchases further in advance and calculate a more accurate budget.
3. Reduce costly write-offs
All quarries need accurate information on stockyard tonnage to fulfill work orders and be financially solvent. But too often, big write-offs have been par for the course. Even when outrageously high, they’re an accepted status quo. Using drones to measure stockpiles gets you highly accurate volumes so you can reconcile any accounting discrepancies during an audit.
Using drones to measure stockpiles: the basics
First, fly your drone to capture site data
Before you can take a single volume measurement, you need to fly your drone to capture site data. There are a few ways to do this. “Drone surveying” basically means using a drone to take aerial photos of your site and some form of GPS data and ground control to provide geographical context (aka coordinates).
Flying a drone to survey your site is significantly faster—up to 10x faster, by some estimates—than using traditional ground-based methods. It’s also safer for a drone pilot—whether that’s your head surveyor or someone else in your organization—to stand by and let the drone collect the data than walking the site themselves.
Next, let the photogrammetry software do the work
Once you’ve got the imagery and ground control data you need, it needs to be processed into your 3D model. For all but the most large scale operations, keeping a photogrammetrist on staff is cost-prohibitive. Similarly, processing the data in house is a lengthy manual process that requires specialized software. Often, it also requires a dedicated computer to crunch the data.
Propeller processes drone data for you with a twenty-four hour turnaround, so you can devote more time to other duties. Not only do you get the final model, we give you easy access to data outputs—point clouds, digital elevation models, and more. These can be exported to use in other GIS and CAD programs.
How to use drones to measure stockpile volumes for quarries or mines
Once you’ve generated your model, you can analyze your site using drone data visualization software like the Propeller Platform. Measuring the volume of a stockpile in the Propeller Platform is as simple as drawing a boundary around it.
You can quickly make the types of comparisons in the Propeller Platform that site managers use to measure progress and keep stock of material inventory. But the type of measurement you perform will vary depending on the information you need.
Option 1: Measure volume from a reference level. Set the baseline to a desired figure and calculate your total volume from that level up.
Option 2: Measure using a smart volume, and let the computer do the work. For a smart volume, the platform extrapolates where the base of your pile is. Then, it calculates a total volume from there.
Option 3: Compare volumes between two surfaces. This could be survey to survey in order to see progress over time. Or, you can measure the current surface to a final grade design that you uploaded to the Propeller Platform.
Using the stockpile volume calculator to determine the value of stockpiles
Once you have a stockpile volume, you can enter its known material density into our stockpile volume calculator. Using a simple stockpile volume formula, this tool will help you determine the tonnage, and cost, of any stockpile.
Let’s say, for example, you want to find how much material has been added or removed to a stockpile since your last drone survey.
Simply select the Polygon tool and draw a line around the base of the stockpile. In an instant, Propeller will take the thousands of recorded height samples (aka you digital elevation model) within the boundary of this polygon.
Next, Propeller compares these height readings (from your current survey dataset) to those from your previous survey (at exactly the same horizontal locations). Volume changes are expressed as either positive change, where material has been added (labeled Fill) or negative change, where material has been removed (labeled Cut).
The Net value is the difference between the Cut and Fill. When measuring stockpiles volumes, the Net figure will more or less be synonymous with the Cut, since you are measuring one mound of land above the base elevation. There are plenty of other use cases for the Cut/Fill tool in every industry we service. (More on those below.)
It’s also possible to view changes in stockpile volumes as a cross section. In this case, Propeller reads the recorded height samples from various distinct datasets along a line that have been drawn, and renders the results on an interactive chart.
The measurement process for pit and stockyard volumes is similar to that of quarries and mines. However, having the correct grade blends going through your mill or crusher is essential to your measurement success.
Too often, insufficient input grades are only discovered after the fact, when the final material doesn’t add up to what entered the processing plant. Instead of backtracking, Propeller can be used to monitor your stockpiles before something goes wrong.
We know landfill surveys can be difficult, too. It’s nearly impossible to send someone out to walk those piles. Drone surveying can capture the data you need in hours, not days, without sending someone to walk over dangerous piles.
How to report on your stockpile volume measurements
Forty-eight percent aggregates and mining professionals who responded to our 2020 Earthwork Report listed “material moved” as the metric most important to operational efficiency. That came as no surprise to us. We know that keeping track of material inventory at every stage of a project is critical to smart decision-making on mines and quarry sites.
But having that data available to your organization is only useful if it can be disseminated and shared in a contextual, easy-to-understand format. For instance, financial recordkeepers and auditors probably don’t need to know the tonnage of a stockpile if they have its volume and dollar amount.
Propeller’s Stockpile Reports feature empowers platform users to export customized data in either a PDF or in CSV for importing into another accounting or site management program.
3D blast planning and other drone surveying use cases for quarries and mines
Using drones to measure stockpiles is not the only application for mines and aggregates sites. Before you can build up your stock, you need to extract it. Making decisions with the most up-to-date and reliable information is critical for any site manager, especially when planning and executing blasting work on a mine or quarry site. Keeping your site survey and bench level plans updated and accurate can dramatically improve blast results and significantly reduce drilling and blasting costs.
When planning blast works to fill a specific customer’s order, a volume can be easily identified on the 3D model using the Volume to Reference Level measurement tool. You simply draw a shape around the blast area, set the bench level to “blast to,” and the computer crunches the numbers.
These images also provide a good source of data for visual assessment of blast results like muckpile shape, back damage, distribution, and fragmentation. Plan your post-blast logistics using the fragments’ size and location data. You can also measure pile volume and fragment size, add annotations, and share blast reports with stakeholders directly from the Platform.
With the Volume Compare feature, the blasted volume can be compared against the plan to ensure the right amount of material was extracted. If you have any design or linework, you can overlay that into the model to help with accuracy and quality—and ensure you’re not leaving resources in the ground.
Want to learn more about how drones can streamline your inventory management? Download our guide to Stockpile Measurement and Reports with Drone Surveying.
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