Lasers are helping paleontologists to preserve and understand the footprints
that dinosaurs made in mud or soft soil that later turned to rock.
Light detection and ranging systems (lidars) can map three-dimensional profiles by firing a series of eye-safe laser pulses
from the ground or the air. ;e laser system records pulse
direction and return time, which are combined with GPS
data to create a 3D map.
In an early demonstration at the Red Gulch Dinosaur
Tracksite in northern Wyoming, Ne;ra Matthews of the U.S.
Bureau of Land Management and Brent Breithaupt of the
recently closed Wyoming Geological Museum recorded three-dimensional positions of hundreds of points a second to within
a few millimeters using a portable ground-based laser scanner.
Integrating the laser data with digital photos and a geographic
information system produced a 3D digital map that was accurate to within a centimeter.
;ree-dimensional analysis is vital, and the laser’s ability to measure depth is a big plus. “Tracks are fundamentally
three-dimensional structures,” shaped by how deeply a foot
penetrates the soil as well as by the outline of the foot, says
Phil Manning, a paleontologist at the University of Manchester in Britain. ;e surface of a fossil footprint usually
isn’t the surface the dinosaur stepped on; it’s an impression
made on a sub-surface layer, and its shape depends on how the
dinosaur’s foot pressed into the underlying soil. Mapping them
in two dimensions invites errors and causes information to be
lost. “Ask people to draw lines around a three-dimensional
structure, and they all come out di;erent, because there’s no
sharply delineated line,” says Manning.
Manning’s student Karl Bates scanned the Glen Rose tracks
to obtain three-dimensional data for a computer test. He was
looking to assess whether Bird was right in suggesting that the
tracks indicate a predator stalking its prey, or if the dinosaurs
wandered through the site at di;erent times. ;e digital scan
data will also be a permanent record of the important footprints. Although the Texas museum tracks are now enclosed
in a building, they have experienced some deterioration due
to moisture seeping from the ground below, a leaky roof and
paint applied to the track surface many years ago. ;e tracks
are type specimens of Brontopodus birdi footprints, making
their preservation particularly important for science.
Laser scanning isn’t the only optical technique for collecting trackway data. Powerful new software for compiling 3D
data from digital photographs taken at di;erent angles has
greatly enhanced the old technique of photogrammetry, which
measures the shapes and sizes of objects from two-dimensional
photographs. By combining data from multiple photographs
taken at di;erent viewing angles, the software can reconstruct
three-dimensional shapes. Paleontologists routinely carry cameras in the field, and “anybody with a camera can do photogrammetry,” says Breithaupt. Laser systems, on the other hand,
Courtesy of AMNH Courtesy of Karl Bates
Texas dinosaur trackway which Roland T. Bird thought showed a
predator stalking its gigantic prey. Upper photo by Bird of tracks in
place in Texas. Lower image shows 3D laser scan by Karl Bates of
the University of Manchester.
can be cumbersome, especially for the many sites reached by
hiking miles from a road.
But the biggest issue for laser systems is their cost. Manning’s equipment and software cost 100,000 U.K. pounds—
about $150,000 in U.S. dollars. With paleontology funding
severely pinched, that’s not within many budgets. Wyoming