as permanent targets to provide the control needed to stitch
together discrete scans. Due to the repetitiveness of the shed
structure, spacing the balls in different configurations relative
to each other would improve the geometry and accuracy of the
registration. To further assist registration, columns in the shed
were labeled with large numbers to help identify scan location in
Surveyors controlled the instrument via a tablet computer run-
ning the Android operating system; no bulky laptop was required.
Data was collected onto the instrument’s SD card for easy transfer
to the office. "It was critical that we be able to use Wi-Fi," said
HTD’s Managing Director Edrick Delfos. "The biggest benefits of
the TX5 were its onboard data storage, Wi-Fi controllability, and
its weight and size. This project couldn't have been achieved with
any other system."
The unique setup offered other benefits, including the ability
to measure a stockpile with one overhead scan—a total station
would require three setups from different sides. It also delivered an
image where no flat area was depicted at the top of the stockpile.
Less Physical Toll, Greater Accuracy
The Trimble TX5 enabled HTD to complete its surveys in approxi-
mately 80 minutes—well within the 90-minute window between
trains; a total station survey would take 3 hours. The team also
achieved excellent accuracy due to the number of shots taken.
The scanner observed points at approximately 50 mm (2 in) spacing
and then the data was filtered during processing. This produced a
truer representation of the stockpile's shape than a conventional
survey observing at 5 –10 m (16–33 ft) spacing.
Another factor contributing to greater accuracy was decreased
surveyor fatigue. The Trimble TX5 setup reduced the physical
burden of the environment on the surveyor, improving the ability
to concentrate and make good decisions, which also increased
the likelihood of duplicated accuracy.
What the Client Saw…and Didn’t See
HTD prepared deliverables in Trimble RealWorks software, with
the client receiving a simple contour plot superimposed onto a
skeleton outline of the holding shed, and a numerical quantity of
the volume. Registering and generating the deliverables took just
15 to 20 minutes—with the data being usable in well within two
hours of the survey. While the "how" of the stockpile survey was
significant to HTD, in reality the change in process had little impact
on the client directly. What impacted the client most significantly
was how invisible the survey became on site. Safety-conscious
site supervisors had no need to interact with or monitor the HTD
team, which enabled them to focus on other tasks.
The Trimble TX5 now delivers for HTD each month at the Karara
holding shed; the team is also finding it suitable for taming many
other HTD projects. "We have found the TX5 to be very versatile,"
said Delfos. "We're confident we're going to use it consistently
enough across our projects that we'll achieve a solid return on
the machine very quickly."
See feature article in Lidar News' April issue: www.pobonline.com