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MODERN MINING
October 2015
TECHNOLOGY
A
t the heart of this technical ad-
vance is the ability to conduct
high-quality 3D face profiling
using stereographic image pairs,
providing accurate and detailed
information for better drilling and charging
designs that optimise powder distribution and
reduce the risk of fly-rock.
The high-quality images also provide good
visual assessments and measurements of block
conditions and blast results – often not achiev-
able from the blast elevation or from fixed
elevated viewpoints. This information is partic-
ularly useful to pit-managers, mine surveyors,
planning engineers and blasting consultants.
Working in a number of South African
mining operations – in collaboration with
US expert Robert McClure of RAM Inc and
Terracam (Pty) Ltd – BME has been combining
these technologies to more effectively quantify
blast parameters including drilling quality,
block geometry, back damage, heave profile
and fragmentation evaluation.
The approach involves the use of small
fixed-wing drones (or multi-copters to deliver
oblique views) that are pre-programmed to fly
a grid across a particular area of interest on the
mine site. This is done before and after a blast,
to create accurate and measurable 3D images
for analysis.
Due to the evolution of modern, high
Drones, 3D photos and GPS
take
BME’s Tony Rorke.
It is well known that good blast design ensures an effective distribution of powder that
improves blast results and reduces drilling and blasting costs. Now, through the use of
unmanned aerial vehicles (UAVs or drones), global positioning systems (GPS) and three-
dimensional (3D) photogrammetric software, the field of blast design has been taken
another step forward, as Tony Rorke, Technical Director of BME, explains in this article.
energy-density lithium polymer batteries,
UAVs have become smaller and more afford-
able; and with reliable satellite navigation, they
can safely fly aerial photographic surveys for
up to an hour.
Equipped with small, high-resolution (10-20
megapixel) digital cameras, a fixed-wing drone
can fly at low altitudes and deliver high-pre-
cision, geo-referenced orthophotos of the blast
area. Still images are taken at intervals so that
there is sufficient overlap to generate a 3D topo-
graphic surface, with accuracy relying on the
placement of surveyed ground control points
with sufficient elevation variance. The projects
in South Africa consistently achieve vertical
and horizontal accuracies less than 100 mm
with a minimum of four ground control points.
Once this field information has been col-
lected, analysis is quick and effective; by
incorporating the options into a single pack-
age, a mine can manage their site with more
confidence – making decisions with the most
up-to-date information. Two software applica-
tions are required: one to generate a 3D surface
orthophoto from the UAV images, by creating
dense and filtered 3D data in any format from
ASCII point clouds to raster GeoTIFFs or ECWs;
and survey software to analyse volumes, cut-
lines and surfaces.
The type of blast-specific information
obtained from the photographs are: pre-blast