POPSCI.COM • FALL 2019 93WHAT LIES BENEATHpotentially life- sustaining destinations like Mars or Europa without
disturbing what’s already there.
Wondering if one day we might encounter the crumbling re-
mains of a civilization on an icy moon of Jupiter, I strolled the Via
di Nola during 2018’s hot, dry summer excavation season. In the
evening, after the throngs of tourists thinned and the researchers
laid down their trowels, the shadows around me deepened, as the
high, crumbling walls that flank the old commercial street blocked
out orange light from the waning sun. Two thousand years ago, this
wouldn’t have been unusual; most buildings in Pompeii rose three
or four stories high, submerging the narrow road in welcome shade.
But these upper floors rarely survive today.
As I wandered toward the downtown temple district, and the sky
continued to darken, I heard a low hum from above. I glanced up, and
caught sight of a small drone swooping in low over my head. It flew in
a precise switchback pattern, and I knew instantly this was not some
tourist with a toy. It was the tool of an archaeologist.
THE VIDEO BEGINS AT eye level above Via Stabiana, a major artery
leading to a gate out of northwest Pompeii. From here, the camera-
toting drone passes between densely packed homes that line the
sunken cobblestone road, which is punctuated by tabernas, shops,
laundries, and bakeries. Raised crosswalks of enormous rocks trans-
verse the street. After a couple of blocks, the view broadens, revealing
the complexity of the grid. Beneath Vesuvius’ vivid green slopes, thou-
sands of buildings come into focus—and suddenly it’s obvious that
Pompeii was once a small city as complex as any in the modern world.
“Drones are revolutionizing archaeology,” says Eric Poehler, an
archaeologist from the University of Massachusetts at Amherst, as he
and colleague Steven
Ellis of the University
of Cincinnati show me
the footage on Ellis’
laptop. We’re drink-
ing beers at a hotel bar
as the pair explain how
they fly everyday DJI
drones with built-in 4K
cameras over sites to
capture 3D images. “Over the course of one pro-
grammed flight, we could produce a 4- gigabyte
image with a resolution of 1.3 centimeters per
pixel,” Poehler says, describing visuals so de-
tailed that he can zoom in enough to examine
tiny cracks in the masonry.
Now, Poehler and Ellis can consult their
footage to plan more-precise digs. These high-
resolution charts become the bottom layer
of a digital archive of the area, with each fea-
ture “orthorectified,” or perfectly fitted to the
real- world grid like a building in Google Earth.
Pulling out his phone, Poehler loads the imagery
into an app called ArcGIS, which is a bit like Pho-
toshop for maps. He can create new information
layers on top of the chart, allowing him to draw
their discoveries onto the images as his crew
digs. If Poehler and Ellis find a fast-food joint
(called a taberna), they can doodle a box over it
and name it. They can also layer on finer details,
such as labeling bricks by their material.
The pair use a technique called photogram-
metry to re-create these ancient ruins in 3D.
Off-the-shelf scanning software lets them merge
2D photographs with measurements they’ve
taken on-site to achieve complete environments.
Over many years, Ellis and Poehler’s team has
pieced together full rooms and neighborhoods;
thousands of images (both old and new) of Via
Stabiana now exist as a virtual model of the strip.
Drone footage and digital images, how-
ever, are helpful only above ground. More than
one-quarter of the ancient metropolis remains
buried. So Ellis, Poehler, and the American Uni-
versity’s Barone are using ground- penetrating
radar help to fill in the gaps.
GPR is like a subterranean ultrasound. The
rigs, about the size and shape of lawnmowers,
contain antennas that send electromagnetic
pulses into the earth and collect them after
they bounce off subsurface structures. These
reflections reveal the density of underground
materials. Variations in the patterns show,
for example, the exact place where ashy mud
meets the top of a brick wall.
Though GPR has been a popular tool amongThoroughfare
Bars, shops, and
fast-food joints
once lined the
streets of Pom-
peii. Residents
running errands
would cross the
dirty roads on
raised stone
crosswalks.