Rome was built in a day, with hundreds of thousands of digital photos

September 15, 2009
The Colosseum is seen here in the digital reconstruction. Each triangle is where a person was standing when he or she took a photo. The building's shape is determined by analyzing photos taken from all these different perspectives. Credit: University of Washington

(PhysOrg.com) -- The ancient city of Rome was not built in a day. It took nearly a decade to build the Colosseum, and almost a century to construct St. Peter's Basilica. But now the city, including these landmarks, can be digitized in just a matter of hours.

A new computer algorithm developed at the University of Washington uses hundreds of thousands of tourist photos to automatically reconstruct an entire city in about a day.

The tool is the most recent in a series developed at the UW to harness the increasingly large digital photo collections available on photo-sharing Web sites. The digital Rome was built from 150,000 tourist photos tagged with the word "Rome" or "Roma" that were downloaded from the popular photo-sharing Web site, Flickr.

Computers analyzed each image and in 21 hours combined them to create a 3-D digital model. With this model a viewer can fly around Rome's landmarks, from the Trevi Fountain to the Pantheon to the inside of the Sistine Chapel.

"How to match these massive collections of images to each other was a challenge," said Sameer Agarwal, a UW acting assistant professor of computer science and engineering and lead author of a paper being presented in October at the International Conference on Computer Vision in Kyoto, Japan. Until now, he said, "even if we had all the hardware we could get our hands on and then some, a reconstruction using this many photos would take forever."

Earlier versions of the UW photo-stitching technology are known as Photo Tourism. That technology was licensed in 2006 to Microsoft, which now offers it as a free tool called Photosynth.

"With Photosynth and Photo Tourism, we basically reconstruct individual landmarks. Here we're trying to reconstruct entire cities," said co-author Noah Snavely, who developed Photo Tourism as his UW doctoral work and is now an assistant professor at Cornell University.

Other co-authors of the new paper are Rick Szeliski of Microsoft Research, UW professor Steve Seitz and UW graduate student Ian Simon.

In addition to Rome, the team recreated the Croatian coastal city of Dubrovnik, processing 60,000 images in less than 23 hours using a cluster of 350 computers, and Venice, Italy, processing 250,000 images in 65 hours using a cluster of 500 computers. Many historians see Venice as a candidate for digital preservation before water does more damage to the city, the researchers said.

Transitioning from landmarks to cities - going from hundreds of photos to hundreds of thousands of photos - is not trivial. Previous versions of the Photo Tourism software matched each photo to every other photo in the set. But as the number of photos increases the number of matches explodes, increasing with the square of the number of photos. A set of 250,000 images would take at least a year for 500 computers to process, Agarwal said. A million photos would take more than a decade.

The newly developed code works more than a hundred times faster than the previous version. It first establishes likely matches and then concentrates on those parts. The code also uses parallel processing techniques, allowing it to run simultaneously on many computers, or even on remote servers connected through the Internet.

The new, faster code makes it possible to tackle more ambitious projects.

"If a city reconstruction took several months, it would be just about building Rome," Seitz said. "But on a timeline of one day you can methodically start going through all the cities and start building models of them."

This technique could create online maps that offer viewers a virtual-reality experience. The software could build cities for video games automatically, instead of doing so by hand. It also might be used in architecture for digital preservation of cities, or integrated with online maps, Seitz said.

In the near term, the "Rome in a Day" code could be used with Photo Tourism, Photosynth or other software designed to view the model output.

More information: The project Web site is grail.cs.washington.edu/rome/ .

Source: University of Washington (news : web)

Explore further: Apple Updates iPod photo Lineup

Related Stories

Apple Updates iPod photo Lineup

February 23, 2005

Apple® today updated its iPod® photo lineup by introducing a new slim 30GB model, holding up to 7,500 songs, for just $349 and a new 60GB model, holding up to 15,000 songs, for $449. Designed to take your entire music and ...

Analysis of Flickr photos could lead to online travel books

April 28, 2009

(PhysOrg.com) -- Cornell scientists have downloaded and analyzed nearly 35 million Flickr photos taken by more than 300,000 photographers from around the globe, using a supercomputer at the Cornell Center for Advanced Computing ...

Recommended for you

Interactive tool lifts veil on the cost of nuclear energy

August 24, 2015

Despite the ever-changing landscape of energy economics, subject to the influence of new technologies and geopolitics, a new tool promises to root discussions about the cost of nuclear energy in hard evidence rather than ...

Team creates functional ultrathin solar cells

August 27, 2015

(Phys.org)—A team of researchers with Johannes Kepler University Linz in Austria has developed an ultrathin solar cell for use in lightweight and flexible applications. In their paper published in the journal Nature Materials, ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Sauvignon
5 / 5 (1) Sep 15, 2009
The data sets generated by this system should definitely be added to Google Earth! :-)
Fazer
not rated yet Sep 15, 2009
I think that technologies like this WILL be added to Google Earth, or a similar service, which will then be the basis for an augmented Earth that we will use for anything from simple navigation to actually viewing as a layer over reality that we view through glasses or contacts.

How long before they outlaw "viewing while driving"?
mckddd
5 / 5 (1) Sep 15, 2009
The next step should be to actually reproduce dense 3D reconstructions from the photos and point clouds. Then decimating the resulting polygon meshes down to polygon counts that would be suitable for display in graphics pipeline via geometric fitting operations.
bredmond
not rated yet Sep 16, 2009
And we could stitch the photos with surveilance cameras to view the areas in realtime. Then i dont actually have to go to rome, i could just do it in my living room.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.