Drones is helping to accelerate stockpile and inventory survey process in different industries such as mining and construction.

We have always mentioned the usage of drones in measuring stockpiles especially for mining produces, but we have never really gone into how exactly it is done. In this article, we will go into detail how drones are put into good use in the mining industry to hasten their operations.

Stockpile management is important and a critical aspect on the site, yet the measuring process can be expensive, time-consuming and sometimes dangerous to the workers.

This can be a bit of a dilemma to most of mining companies as the conventional way of measuring stockpiles can be very time consuming whereas they would need fast results measurement to make decisions accurately.

The traditional stockpile measurement methods range from bucket counts and visual guesses to slightly more informed measurements based walking wheel length and height of the pile. These methods are riddled with inconsistencies, incorrect assumptions, and data entry errors, leaving companies without reliable data to make smart business decisions.

Bad data causes a negative ripple effect through the entire organization. It can create frustration and tension between operations and finance teams, unexpected costly write-offs, and eats away at profits.

How drones are flown in stockpile measuring operations

When using drones in mining operations, there are few factors that have to be taken into consideration in order to get the best accuracy out of the data captured.

There are three main parameters that has to be taken into account when flying the drone; time of the day, height of the drone and the flight path.

The recommended flight path for the drone when estimating the stockpile is to fly parallelly, not in crisscross or crosshatch.

Parallel flight pattern is sufficient to capture accurate data set while there’s no evidence or case studies that have proven flying in crisscross or crosshatch would help to increase the accuracy of the data.

Next, the best time to fly is actually when there’s high visibility and low wind flow. Generally speaking, that would be around mid-day or noon. This is due to the fact that the shadow of objects is much shorter at noon, at this will allow the stockpile baselines to be clearly seen.

Baselines are important when measuring to material mass as it is a measure of the accumulation parameters.

Besides that, the optimum height would be around 3 times higher than the highest point of the stockpile. 

There are a few other factors such as the image overlay and usage of ground control points (GCP) to guarantee more precise results.

Data processing

Data processing is the most crucial process when measuring material stockpile. There are many factors that can inherently affect the outcome of the results, which will influence the decision making heavily.

Once all the data was collected and uploaded, the software will use the raw collection of GPS points to estimate the shape and elevation of the pile.

To start the processing, 3D points across a given stockpile is measured. Normally, in this practice, we plotted the 3D points which can be numbered up to millions, not hundreds—as in traditional forms of stockpile analysis, which means you will get highly accurate measurement of area and volume.

Then, we would need to identify the type of stockpile on the site that was captured by the drone. Generally speaking, there are three types of stockpiles buildup; standard, ram and bin.

Standard stockpile is the most generic stockpile type. It is constructed with basic bucket loading and dumping techniques.

Image via Pix4D

Ramp stockpile is constructed high, with a narrow ramp, and is optimal for storing a large amount of materials in a very limited area.

Image via Pix4D

Bin stockpile is a common stockpile type. Materials are stored in a row of three-sided bins, with enclosures consisting of a hard floor and walls. It is the best solution to keep different materials separate.

Image via Pix4D

After determining the type of stockpile accumulation, we then will need to predetermine the base surface or the base plane of the pile. Aerial imagery processing software needs this info to accurately calculate the volume of the material.

There are normally two types of base plane of stockpile: clear boundaries and partially non-visible boundaries. A stockpile’s boundaries can be hidden by either by intersecting stockpiles or by a wall.

Image via Pix4D

Aerial imagery processing software will have options for you to actually optimise the processing software to increase accuracy.

Viewing results

After the processing part has been completed, it’s naturally the time for you to present the data as a report for further actions.

Below is an example of a stockpile measurement report.

Image via Propeller Aero

Not only the volumetric measurement will be shown, other dimensions such as area, perimeter, and ground elevation level will be shown.

This information can be used extensively to make logistic and operational decision. Questions such as, ‘Is the current stockpile of materials is sufficient for the project?’, ‘What is the rate of material consumption and does it tally with the progress?’ can be answered just by analysing the measurement results. 

Bottom line

Stockpile measurement and surveying with drones has been proven effective by providing accuracy and cutting off the time cost.

In most cases, using drones can cut off the time cost up to 60 per cent. Traditional stockpile measuring process would involve personnel walking around the site that would take up to 8 hours of operation compared to 3 hours when using drones.

Other than that, drones in measuring stockpiles can help to reduce capital investment, improve reporting, streamline inventory material audit and reduce manpower reliance.