Contruction Today - July/August 2017 - 18
Mapping and Modeling
In construction modeling, teams want
good-quality data fast and at a low cost. With
ground scanning, they might get one or two
of these three. With a drone, they get it all.
"With drones, the speed of capture is quick,
the quality is very accurate and the quality of
information is fantastic," says Grant Hagen,
virtual design and construction manager
with The Beck Group.
Drone operators can pre-program a route
for a flight over a construction site, and on
one battery charge and 15 minutes in the
air, it will capture images every few seconds,
automatically assign them to a GPS-based
grid. The only physical labor involved is
painting a big X on the ground to give the
drone a ground-control reference point that
increases accuracy and keeps objects in scale.
Back at the office, the images can be exported into processing software that automatically
creates a 3-D map and model in a process
operators can pre-program a
route for a flight over a construction site.
CONSTRUCTION-TODAY.COM JULY/AUGUST 2017
known as photogrammetry. The software uses an algorithm to stitch
all the photos together, matching up pixels based on the GPS position
of the drone and triangulating each in space to make a three-dimensional "point cloud." This forms the foundation of a computerized 3-D
landscape, allowing the preconstruction team to conceptualize how
the building will sit on the actual contours of the land.
The drone-capture and mapping process enhances the existing workflow by capturing more information more quickly and
efficiently. Traditional ground scanning requires about 20 scans,
which take about 10 minutes each before the scanner has to be
physically moved to a new location and set up again. Once the
ground scans are complete, technicians use a time-consuming
process to match up the scan points, connect them all together and
create one concise model.
A drone can achieve the same level of quality as a laser ground
scanner costing six figures, but with just a four- to five-figure price
tag. A drone scan also shows much more detail than a ground scan,
as the ground scan is limited to a point of view that's ground-level.
Hagen says that The Beck Group finds many uses for drone scans,
including overlaying engineering, architectural and utility plans
onto aerial site photos, allowing for more accurate modeling and
estimating much earlier in the preconstruction process. Drone scans