It's the world's oldest and largest jigsaw puzzle -- an ancient
map of Rome in 1,200 fragments of marble. Archaeologists for
centuries have tried to painstakingly piece together the sculpture,
fragment by fragment.
Now, computer wizards at Stanford University say they have
created a software program that holds the key to the puzzle and the
ancient city.
At the heart of the program are three-dimensional scans of the
fragments and algorithms to find possible matches. Already the work
has produced several dozen probable and possible matches.
``They've advanced farther and faster in the last months than we
have in centuries,'' said Roman archaeologist Margaret Laird, a
visiting lecturer at the University of Chicago. ``These new matches
are going to change a lot of what we know about the city of
Rome.''
The undertaking is a five-year study conducted by Marc Levoy, an
associate professor of computer science and electrical engineering
at Stanford, to be completed by the summer. The findings and
interactive 3-D models of the fragments are online, allowing
scholars as well as elementary-school students unprecedented access
to the monument.
It's the first time anyone has applied technology to piece
together the ancient puzzle. Short of a 1961 book that's now out of
print, the project's Web site is the only place where archaeologists
will be able to examine each fragment of the map, known as the Forma
Urbis Romae.
Levoy thinks the advance may shepherd a ``revolution in
computational humanities,'' where technology and the arts
intersect.
``There is a trend toward putting knowledge online, where it can
be searched by anyone,'' said Levoy. ``Google is the encyclopedia of
tomorrow. A kid working on his sixth-grade history report of Roman
aqueducts now has access to information you'd find in a graduate
library.''
The project started in 1999, when Levoy and a group of students
went to Italy to scan and build a 3-D interactive model of
Michelangelo's ``David.'' As a side project, they went to Rome and
scanned the fragments of the ancient map, working around the clock
and sleeping in shifts to meet a deadline.
The third-century map itself is a feat of cartography. It
detailed nearly every architectural feature of the city, from large
monuments like the Colosseum to shops, apartments and even
staircases. The completed map, made up of several marble slabs,
measured 60 feet by 43 feet and hung in one of the grandest
monuments of the ancient city, the Templum Pacis. Today, only about
15 percent of the map survives -- but it includes core parts of the
city.
One every few years
For centuries, scholars have visually matched up the heavy pieces
of marble, some weighing several hundred pounds. In modern times,
one match has been found every few years -- a cause for huge
celebration in the academic world.
The software program finds an average of one match a month.
Graduate student David Koller, who wrote the program, likens it
to one that tries to piece a broken vase back together. The first
piece of software he wrote tried to find matches by looking at the
sides of each map fragment. Alone, that didn't work because many of
the sides have eroded over time.
Then he wrote other algorithms that took into account factors
such as the thickness of the fragments and the distinct veins
running through the marble. The program also takes, for example, a
column apparent in one fragment, notes where and in which direction
it leaves the piece and then searches other fragments for
complementary features.
``The computer is using the same cognitive process that a human
uses to put a jigsaw puzzle back again,'' said Koller. ``It just
does it a lot faster and with more pieces.''
In June, Koller was convinced he found a match. He and a small
group went back to Italy and opened up the locked crates where the
fragments are kept. They put the two pieces together.
``There was no question it fit,'' said Koller. ``You can feel it
lock into place in your hand.''
The pieces depict the Circus Maximus, the stadium where chariot
races took place. The lines that connect the fragments make up the
road where Romans would march in ceremony after a triumph.
Since then, Koller has found a dozen other matches that he thinks
have a 98 percent probability of fitting and several dozen others
that are possible matches. The team is eager to improve its odds by
applying another set of algorithms used in the Human Genome Project,
to bridge large gaps between markers on DNA sequences. These new
algorithms would put together pieces that don't perfectly fit now
because of gaps caused by erosion.
Surprise and delight
At a conference about the map last month, the findings were
presented amid gasps and delighted laughter.
``We're not going to solve the whole map,'' said Levoy, who is
now looking into underwater imaging. ``It's on the Web. It's now
available for other scholars around the world to try to solve the
map.''