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Processing UAV acquired data
by Faith Beta and Ajay Harduth, RocketMine
This article shows how RocketMine acquires data, the quality and accuracy of the data acquired, and how the
data is processed into various formats suitable for different customer requirements.
I
n 2014 RocketMine Aerial Data
Solutions (RocketMine) became one
of the first companies licenced to
operate and own remote pilot aircraft
systems (RPAS) in South Africa. The
company offers a comprehensive
solution for aerial data acquisition,
processing and dissemination. An
integral part of RPAS photogrammetry
is the actual data that is acquired from
the surveys. Because data collection
has been made simple using RPAS
technology, energy is now focused on
analysing and using the data collected.
RocketMine works closely with the
mining, agriculture, GIS, and urban
planning industries. It is involved
with sourcing the equipment and
technology to deliver accurate data
according to clients’ specifications.
The industries they currently serve
are the mining industry (coal,
platinum and gold), quarries and
telecommunications. Projects have also
been completed in the agriculture and
construction industries.
Fig. 1: Area identified and surveyed by both GPS and an RPAS.
This means different types of data
is used differently by the various
industries. The methodology
RocketMine uses to acquire data is
not the one-solution-fits-all kind.
It is tailor-made to suit the clients’
environment and output expectations.
Through years of experience and an
expert team, the company knows what
solution best fits which environment
and industry.
The equipment used for the acquisition
of data is dependent on the type of
data that is acquired, and the outcomes
that are anticipated. Fixed wing RPAS
are used mainly for surveying and
large-scale aerial photography. The
sensors used on the fixed wings are
(but not limited to) red, green and
blue (RGB) cameras and near-infrared
spectroscopy (NIR).
The multi-rotor RPAS is used mostly for
inspection and small scale photography.
The sensors in the multi-rotor are
(but not limited to) thermal and RGB
cameras and multispectral sensors.
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Fig. 2: Data plot acquired by GPS measurements from surveyors.
Generally, the data acquired by RPAS
in the mining industry are used for
calculating stockpile volumes, mapping
steep, inaccessible inclines, compiling
optimised blast designs, and managing
pit and stockpile changes from a
remote location, as well as monitoring
surface stability safely.
Data accuracy: A case study
The following case study was conducted
by a RocketMine client to compare and
contrast the accuracy and the quality of
data acquired by RPAS as opposed to
the traditional method of GPS. Accuracy
is particularly important in areas of
difficult, complex, or loose terrain, busy
roads, and areas where there may be
undetonated explosives from blasting.
The aim was to compare RPAS data to
traditional terrestrial methods. After a
coal mine was identified for the survey,
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a blast profile was designated, and
pre-marks were placed around the area
of interest. Surveyors initially surveyed
these points using GPS instruments,
before RocketMine conducted an RPAS
survey on the same blast area. The
data from the two surveys were sent
for analysis.
Analysis
What took the terrestrial surveyors hours
to collect and process, took RocketMine
25% less time to collect and process.
In the terrestrial survey the surveyors’
personal safety was of concern as they
were walking among loose rocks and steep
inclines, and as there was no guarantee
that there were not undetonated
explosives around the area. There was
also a high wall the surveyors could not
climb over or take readings from.
In the end, the RPAS survey contained
more detail than the GPS survey. The
RPAS was able to take measurements
from above the high wall, whereas the
GPS was unable. After plotting the data
from the RPAS measurement, the survey
did not move from the designated area.
Thus, in terms of geo-referencing, the
aerial survey was accurate.
The mapped data results are depicted in
Fig. 2. After making the comparison, the
client concluded:
•
RPASmeasurementsdonotundergo
a geospatial (positioning) shift.
•
Duetolooserocksandbigboulders,
certain areas could not be accessed
by GPS surveyors walking a round the
blast, but the RPAS was able to safely
cover all areas.
•
Intermsofhumansafety,RPAS
measurements eliminate the exposure
of unsafe ground, loose rocks and
other obstacles that may pose to
surveyors who have to walk and take
measurements.
•
UsingRPAS,ittakeslesstimefor
data to be collected and eliminates
the need for surveyors to spend many
man-hours walking around the same
area.
•
Dronemeasurementtakesinmore
detail accurately, including but not
limited to the areas below obstacles,
such as high walls in this case.
•
Additionally,varioushigh-quality
outputs can be generated from the
information gathered by the RPAS,
in this case the team got a PDF file
image in 3D.
Acquiring data for clients
As soon as measurements are acquired
by RocketMine, the data measured
is processed centrally. Depending
on the industry where it is needed,
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Fig. 3: Data plot acquired by RPAS measurements.
Fig. 4: A summary of the cross-sections from the surveyor’s measurements.
it is presented in a format that is
tailor-made for consumption by the
unique user. RocketMine does an
analysis of what the client wants and
decides on the best methodology for
processing of the data. They then give
clients advice on the best type of RPAS
data for their needs. For example, a
client may need to track the movement
of their equipment for purposes of
accountability, and they are given a
heads-up on how the project will be
carried out from its inception to its
completion. They are also told what
type of data will be produced, and
how long it will take.
RocketMine offers clients solutions
in two ways. First, with an A-Z
approach in which RocketMine does
everything for the client – from
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supplying the RPAS, the operating
personnel, acquiring the data, to
processing the acquired data and then
giving the client a finished product.
Secondly, an integration solution, in
which RocketMine offers a part of their
services as an outsourced part of the
client’s project. This means that they
fit into the client’s team at the point
of need. The client’s team determines
where the company’s team comes in,
what they should bring, and how their
input should blend in with their existing
project.
Whatever the case may be, RocketMine
has the capacity to start and finish
projects in as little time as possible.
They normally require very little input
from the client. Depending on the
information the client needs and gives,
work can start and finished on the
same day they meet with the client.
Types of data acquired
RPAS data is always acquired in the
form of images. It is then imported into
RocketMine’s specialised professional
photogrammetry software for
processing. Because image quality
is important, image correction and
enhancements are also performed so
that the images produced are of the
highest quality.
The data is then transformed into any
of the following types of products,
depending on the client’s needs:
•
•
•
•
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Point clouds: sets of data points
in a 3D coordinate system that
represent the external surface of a
terrain or object.
Orthomosaics/orthophotos/images:
files containing aerial photographs
geometrically corrected so that the
scale is uniform.
Digital elevation models (DEMs):
files containing elevation values
representing terrain height over
a specific area of the Earth. It is a
“bare earth” elevation model devoid
of vegetation, buildings
and other objects that are above
Earth’s surface.
Digital surface models (DSMs): files
containing elevations that include
buildings, vegetation, power lines
and other above-ground objects.
The ground is only seen when there
is nothing else on it.
•
3D PDF images: files with images
that provide a depth perspective.
•
Video fly-throughs: videos showing
movement of the camera through a
predefined path.
•
Normalised difference vegetation
index (NDVI): images containing
remote sensing measurements
Area/department
Industrial application of data acquired
Pit and dump management
Short-term
planning
Communication of daily/weekly mining plans
Haul route surface optimisation
Storm damage assessment and control
Haul road, dump and pit design
Geotechnical
Long-term
planning
Surface stability monitoring
Joint mapping
Control for mining in void areas
Mapping of steep inaccessible inclines
Up-to-date surfaces for optimised blast designs
Drill and blast
Pre- and post-blast data
Identification of misfires and wall damage
Geology
Stock pile management
Grade control and exploration planning
Drainage and water management
Hydrology
Watershed, drainage basin and water flow mapping
Thermal detection of ground water inflows
Tailings dam management
Feasibility studies
Construction
Leach pad, dam wall and platform construction quality control
Progress monitoring and reporting
Mineral
exploration
Resource calculation
Geophysical and watershed/catchment area modelling
Supporting photography
Reporting
Erosion detection
Heritage and
environmental
management
Vegetation change tracking
Inundation tracking
Slurry pipeline stability and leakage detection
Game counting
Surrounding community mapping
Cadastre
Property rights definition
Legal
Change detection
Security
Incident evidence capture
Corridor and boundary surveillance
Community relations/marketing
Community
Impact reporting
Oblique imagery
Table 1: The types of data RocketMine acquires for the mining industry.
that assess whether the target
being observed contains
live green vegetation or not.
These are normally used for
rehabilitation areas.
RocketMine specialises in point clouds,
orthomosaics, and DSMs.
Data processing
The data acquired is accurate with
a very narrow margin for error. Its
accuracy means that it is generally
delivered to the client within 24 hours
of acquisition, since there is not much
editing that needs to be done. Once the
still images are collected by the RPAS,
they are processed using specialised
photogrammetry software. The process
of optimising images for data purposes
can be loosely translated in four steps.
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Step 1: Exploration and mapping of data.
The RPAS is assembled, prepared, and
put out in the field for mapping.
Step 2: Checking image quality. The
quality of the images can be checked and
adjusted even when the RPAS is still in
the field.
Step 3: Generating orthomosaics,
3D models and point clouds. Once
the images have been downloaded,
generating the desired output is an
almost fully automated action. The
operator can generate the desired
output from the drone’s images. The
photogrammetry software handles all
the calibration and processing, and in
a few clicks the operator has the
desired output.
Step 4: Assessing and editing images.
This steps improves the quality of the
images provided, and the user can add
text and other objects directly into the
software. The added objects will then be
added to the final generated output.
Fig. 5: A summary of the cross-sections from the RPAS measurements.
Table 1 shows the types of data
RocketMine acquires especially for
the mining industry, and Table 2 shows
the various types of data that RocketMine
has previously acquired and has
capacity to acquire for their clients in
other industries.
Other RPAS data uses
Lost time injury (LTI): LTIs are injuries
that occur at the workplace that result
in an employee’s inability to work in a
given time (loss of man hours). Instead
of sending a surveyor to survey the
extent of the damage or loss, a drone is
deployed to safely and swiftly carry out
the assessment. This is to avoid loose
ground, undetonated explosives, and hilly
terrain if a human being was to go to the
same place.
Investigations: When there has been
vehicle accidents, a drone can be
deployed to get a full view of the impact
instead of having a human navigate the
impact zone. This minimises the risk of
injuries and possibly fires.
Both these investigations use visual,
using thermal and RGB sensors.
Fig. 6: A closer look at the wall that the RPAS was able to measure.
Industry
Plant counting
Canopy measurement
Agriculture
For more information about RocketMine,
RPAS data outputs and other
projects the company does, visit
www.rocketmine.com.
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Vegetation index calculation
Livestock detection
Plant health reports
Stockpile evaluation
GIS
Volume calculation
Production and works
Monitoring
Disaster monitoring
Conclusion
Data acquired by RPAS has the ability
to increase productivity and capacity
since the tasks traditionally done by
many people over a long period of time
can now be done in a short time space
with minimum personnel.
Industrial application of data acquired
Urban planning
Stockpile calculations
Work and progress
Monitoring mapping
Table 2: The types of data RocketMine acquires for other industries.
References
[1] Drones for Mining: www.sensefly.com/
applications/mining.html
Contact Ajay Harduth,
RocketMine, Tel 086 112-3738,
[email protected] 
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