Home' Position : Position Jun Jul 2016 Contents The more, the better
The process of taking photographs and
turning them into 3D coordinates is no
new feat. Photogrammetry is a term that
has been in industry use since the 1940s-
almost as long as the commercial aviation
industry has existed. Photogrammetry—
taking multiple overlapping photographs
and inferring geometry between them—
has theoretically always been possible.
Practically however, those wishing to
practice photogrammetry have lacked the
hardware and software required to perform
it in a commercial setting. Enter 2016 when
a decade of rapid evolution in computing –
both in CPUs and GPUs – has allowed the
development of photogrammetry software
that can turn a set of photos of an object of
any scale into a 3D model.
Underlying this process is software
called ContextCapture, a product of
infrastructure software providers Bentley
Systems. Originally called Smart3DCapture
and developed by Acute3D, ContextCapture
is the result of the acquisition of the start
up in early 2015. While Smart3DCapture
technology was being used by some of the
world’s largest mapping organisations and
still is, the shift to ContextCapture seeks
to open up the technology to the wider
commercial market, including surveyors of
all scales of operation.
Surveyors became a key target soon after
areial surveying was opened to the wider
market following the advent of remotely
piloted aircraft systems (RPAS). While data
capture is useful from above by RPAS or
manned aircraft, it is now also practical
to perform this on the ground level using
nothing more than a handheld camera.
“There is very little difference between
capturing images from an aircraft over
a city and capturing images from a UAV
over a small site,” says Pascal Martinez of
Bentley Systems, who joined Bentley with
the Acute3D acquisition.
“When joining Bentley our first thing
was to expand ContextCapture to the
entire surveying industry,” he says.
For readers of Position, this prompts
the usual questions – ‘Is it accurate?’, ‘Is
it reliable?’ First we need to understand
that the software itself works without
any coordinate information- relying only
on the triangulation created from the
geometry inherent in the photographs.
The better the optical properties
of the camera and the quality of the
positioning, the better the quality
of the result. However, the final
accuracy comes predominately from
the comprehensiveness of the photos
acquired. As a general rule, the more the
better. Keep in mind, however, that from
the initial photography right through to
the 3D model, the entire process is left is
left in the hands of the software.
“It’s a fully automated process,”
explains Martinez. “The first part of the
process is Aerotriangulation – figuring
out all the positions and rotations of all
the photos in space. Then the geometry is
extracted from the texture provided by the
“It really depends how good the dataset
is that you are using as an input. Good
means that photos are sharp and adapted
to the desired resolution.”
Using ContextCapture, the relative
precision is 1-2 pixels, meaning that if you
want to capture detail to 2mm, then you
will need to capture pixels at around the
1mm level. Theoretically then, it follows
that the accuracy is defined entirely by
the mode of data acquisition, meaning
any level of accuracy is possible- even
sub-millimetre. The only thing that does
restrict the accuracy is the sensor used
and the way positions are geo-referenced.
When you do wish to geo-reference
or designate a scale, the software
supports a number of methodologies.
Each photograph can be geo-referenced
using any combination of GNSS or
IMU, including on handheld devices.
Alternatively, control points can be
applied within the survey to manually
improve the global accuracy of the survey.
Bentley Systems are also working on a
way to incorporate point clouds acquired
from scan data with 3D models generated
It is worth noting that coordinate
information is not required for each
photograph, meaning that data capture can
occur where GNSS observations are not
achievable and that models can be created
by those whose skillset includes no more
than being able to take a photograph. Nor
is investment in heavy computing power
required, since the modelling engine is
supported by the dedicated ContextCapture
Center cloud-based processing service.
From there, the Acute3D Viewer can also
be used to share the resulting 3D model.
“We don’t see the world as point
clouds,” explains Martinez. “We see
the world with surfaces, textures, and
occlusions –and that is exactly what
ContextCapture is doing.”
“People want to turn information
into value. And to do this we need to be
compatible with the rest of the Bentley
The .3mx file resulting from
ContextCapture can be immediately
integrated into most 3D modelling, GIS,
and web mapping applications, including
Bentley’s flagship 3D modelling software,
Microstation. From there, the applications
Just the beginning
In Onkaparinga, AEROmetrex took a
stunning natural coastline and modelled it
with accuracy and a strong sense of reality.
But Onkaparinga is just one of many
impressive undertakings of AEROmetrex.
In 2015, they were selected to perform
the comprehensive 3D modelling
performed for the visit of Pope Francis
to Philadelphia. In planning the event,
the organisers needed to coordinate with
Philadelphia’s public services, as well as
the U.S. Secret Service.
To support this, AEROmetrex acquired
photographs of the entire surrounding
urban landscape, using both aerial and
ground-based observations. The survey
informed—among other things—the
details for the 56,400 temporary structures,
main and secondary stages and event
seating, 33 miles of security barricade
perimeter, special U.S. Secret Service
security requirements and the impact of
local road closures to pedestrian traffic
flows. The impressive results (see here for
gained the Adelaide-based team well-
deserved international recognition.
For now however, AEROmetrex are
focussing their efforts nationally, having
started a project to capture every Australian
CBD in 3D- all to 50mm X,Y,Z accuracy.
Organisations of all types have shown
such a strong interest in the service that
AEROmetrex have made the strategic
decision to begin undertaking the services
on their own accord.
“We intend to cover every Australian
city – at least every CBD,” said
Mark Deuter, Managing Director of
“We have encountered such a diversity of demand
that we’re just going out and doing it. Sometimes
there isn’t any direct client as such.”
- Mark Deuter, Managing Director at AEROmetrex.
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