Washington, September 16 (ANI): The ancient city of Rome can now be virtually built within a matter of hours, thanks to a new computer algorithm developed by an Indian-origin University of Washington researcher.

The new program can digitise hundreds of pictures of the city, including the Colosseum and St. Peter's Basilica, in just a matter of hours.

It 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 university researchers behind this innovation have even built a digital Rome from 150,000 tourist photos, tagged with the word "Rome" or "Roma" that were downloaded from the popular photo-sharing Web site, Flickr.

Computers analysed each image, combined them in 21 hours, and created a 3-D digital model.

The model can help one 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.

He said: "(Until now) 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."

In addition to Rome, the researchers have 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.

The novel technique can create online maps that offer viewers a virtual-reality experience.

The software can even build cities for video games automatically, and may also be used in architecture for digital preservation of cities, or integrated with online maps.

The research was supported by the National Science Foundation, the Office of Naval Research and its Spawar lab, Microsoft Research, and Google. (ANI)