Modern Quarrying Q3 2019

of the application of the already surveyed data, Van Rensburg says given the typical small areas to be surveyed for quarry operations, Aquila typically captures the complete site on every survey. Subscribing to a regular aerial survey service with Aquila Drones, however, creates the potential for any quarry or mine operation to expand the deliverables to include much more than only volumetric results of stockpiles and quarry measurements, which is what SPH Kundalila has done at Bridgetown Dolomite Mine. “Monthly surveys of an operation provide us with data that, through further processing, can become valuable management tools. The client could identify an area of interest where they would like to review what has changed over a specific time and how. An automated analysis is then performed by comparing two historic data sets which gets overlaid and provides a visual index of the change. This could be used to monitor changes and highlight material moved over a defined period. Accurate measurements and calculations can then be performed depending on client requirements. These could include any area on site or inside the quarry pit,” explains Van Rensburg. Dust suppression Another innovative technology that has come out of Bridgetown Dolomite Mine and Van Rensburg’s relationship is a revolutionary and completely new system for dust suppression, the Atomiser. It is a nozzle spraying system that has water and high-pressure air from a compressor. With its high pressure, it atomises water particles to make a fine mist which captures dust. Bridgetown Dolomite Mine is one of the very first quarry test sites to use the solution in a fixed crushing environment in South Africa. “We will install the nozzles on strategic transfer points on crushers or wherever dust is generated on the plant. We will be able to regulate the amount of water and air the system discharges,” says Pretorius. At the time of writing, the solution was due

Five Cat 950 wheel loaders are used to stockpile and load customer trucks on site.

AT THE QUARRY FACE

Typical resolution targeted during data acquisition with drones is sub 3 cm ground sampling distance. This is deemed adequate for volumetric measurements for stockpiles.

understand that the process used by Aquila Drones still involves a registered surveyor which forms part of the team in setting up ground control markers. The complete survey 3D model is thus absolute geo referenced accurately to within 2 cm,” he says. The typical resolution targeted during data acquisition is sub 3 cm ground sampling distance. This roughly equates to three dimensional point cloud model accurate to within less than 5 cm. This is deemed adequate for volumetric measurements for stockpiles. Accuracies can however be increased to 2 cm depending on client requirements. “Any surveyor would confirm that the accuracy achieved through a precision aerial survey processed with the industry leading software PIX4D will virtually always yield more accurate volumetric results. This is inherent to the fact that a typical point cloud model would consist of thousands of measurement points on the surface of the stockpile versus only a few typically taken via precision GPS systems,” explains Van Rensburg. Speaking about the expansion

a multirotor solution used for smaller survey areas in the region of 50 ha. The main advantage is the ability to take off and land virtually anywhere. Operation is also simple. The AQRVS is the fixed wing platform typically used to survey larger areas up to 500 ha depending on ground resolution required. Van Rensburg explains that in some cases the perception exists that the land surveyor volumetric calculations are more accurate. “I think it is important for clients to Louis Pretorius, site manager at Bridgetown Dolomite Mine.

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MODERN QUARRYING QUARTER 3 - 2019