Home' Position : Position Dec Jan 2016 Contents there was zero room for any positional
errors in the horizontal or vertical plane:
the embed ring had to be placed and
remain within the construction tolerances
of 5mm horizontal and 2mm vertical.
That required a minimum of four as-built
surveys, which Mr Farrell performed
using the Trimble S8 total station and a
precise optical level.
"Having the total station precision and
the data controller's desktop computer
functionality was really key for this
phase," said Farrell. "I could quickly
reference the relevant control grid, use the
S8 to automatically and accurately shoot
specific points and verify the integrity of
the embed ring in seconds. And during
the main concrete pour, I could monitor
the structure in real time as well."
Indeed, about 330 cubic meters of
concrete is poured into the foundation
-- including the collar around the embed
section -- in a single, continuous pour.
That much volume of material at one time
could cause the ring to shift. To account
for that risk, crews set the S6 on previously
set external grid reference marks to
monitor the embed ring for any significant
movement horizontally or vertically during
the main concrete pour. After the pour, Mr
Farrell completed a survey of eight points
around the top of the embed to confirm if
any movement had altered its position.
There's a tool for that
The technological ability to be rigorous
in measurement detail but efficient
in execution not only gave TGM the
tools to effectively deliver on its initial
project scope, it proved to be the right
combination to manage other tasks as
When Downer EDI needed to upgrade
public access roads to support the
heavy volumes of overweight vehicles
transporting stone, concrete and turbine
components, Mr Farrell used the R8
GNSS receiver to carry out feature
surveys and stake out alignments for the
And when detailed set-out and as-
built data were required for the electrical
substation foundation bolts and concrete
formwork, he brought in the Trimble S8
to capitalise on the instrument's inherent
robotic functionality and high-precision
A significant and critical part of Mr
Farrell's scope was to precisely position
over 100 bolt sets, some of which
contained eight-bolt configurations, which
were cast into the concrete footings.
He used the S8 to set pins on grids to
position the bolt lines, and once the steel
was placed and the bolts were erected, he
performed a check survey of all the bolt
locations prior to the pour and adjusted
any that were outside position tolerances.
The slab was then poured and Farrell
confirmed the final position of the bolts in
the concrete formwork.
Performing this essential work without
survey technology would have been
significantly labour intensive and increased
the potential for miscalculating control
points to set the bolt lines, said Farrell.
"With the S8, I can lay out bolt patterns
by simply inputting into the controller the
point number for a specific bolt and the
instrument automatically turns to where it
should be," he said. "Without that feature,
I'd have to turn specific angles manually
and manually input calculations to lay the
features out. That's really laborious and it
leaves a lot of room for error."
With the small foundational
elements secured, crews could then
complete constructing the electrical
substation, using the watchful 'eyes' of
the surveying equipment to ensure the
accuracy of the building.
Having that ability to accurately match
the ebb and flow of myriad crews' survey
needs with fluid, integrated technology
was a key enabler to help successfully
move the Mt Mercer Wind Farm from the
ground floor, up, said Mr Farrell.
"We couldn't have engaged in a project
of this scope without a reliable GPS unit,"
he concludes. "Nor would we have been
able to provide the accuracies required,
as quickly as required, without precise
total station technology. But the most
significant advantage in the field was the
ability to simultaneously run the R8 in
conjunction with the total stations and
seamlessly integrate and manage the data
with one survey controller. That gave us
the ability to run the whole show with one
piece of equipment." ■
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