"In this case the layer is above ground and not below where it should be" from an archaeological point of view, said Bernard Frischer, the director of the University of Virginia's Institute for Advanced Technology in the Humanities.
had planned to activate the feature on Wednesday morning, but a spokesman said there would be a short delay because of technical difficulties.
By Wednesday night, however, the feature was up and running. (Web visitors in the United States can watch a video demonstration of the feature at earth.google.com/rome.)
For nearly three decades Professor Frischer has been the driving force of an effort to bring ancient Rome to virtual life.
The Google Earth feature is based on his
Rome Reborn 1.0, a 3-D reconstruction first developed in 1996 at the University of California, Los Angeles
, and fine-tuned over the years with partners in the United States and Europe.
Of the 7,000 buildings in the 1.0 version, around 250 are extremely detailed. (Thirty-one of them are based on 1:1 scale models built at U.C.L.A.) The others are sketchier and derived from a 3-D scan of data collected from a plaster model of ancient Rome at the Museum of Roman Civilization
Archaeologists and scholars verified the data used to create the virtual reconstruction, although debates continue about individual buildings.
"We're happy when scholars disagree with us," Professor Frischer
"It makes for good scholarship."
The Rome Reborn model went through various incarnations over the years as the technology improved.
Originally it was developed to be screened in theaters for viewers wearing 3-D glasses or on powerful computers at the universities contributing to the project, rather than run on the Internet.
That all changed in June 2007, when Professor Frischer
Reborn at a news conference in Rome.
The next day he
received a call from Google Earth
said that now that Ancient Rome 3D would be available to millions, he
hoped it would become a scholarly work in progress, open to changes and contributions from other scholars.
"The great thing about digital technology," he
said, is that it can be updated constantly "and supports different opinions."
"There's always something to discover," Professor Frischer
paused, then added, "Please don't make me say it, but, after all, Rome
wasn't built in a day."