VOA常速英語：激光照相機有助于保護歷史建筑

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George Putic

January 15,2015

Restoring a historic building to its original shape usually starts with taking detailed measurements of all of its elements - doors, windows, stairs, chimneys - so they can be taken apart, repaired or replaced with their exact replicas. But exact measurements that used to take months can now be done in a few days, thanks to the advanced technology of laser cameras.mAn experimental project is being conducted at a historic location on a hill overlooking Washington, D.C.

The beautiful cottage built around 1842 in the Gothic Revival style was used as a summer retreat by President Abraham Lincoln during the Civil War.

In one of its rooms, Lincoln signed the Emancipation Proclamation, effectively ending slavery in the United States.

Preserving this piece of history is important, so a small team from Ithaca College in New York spent about two weeks in the cottage with a laser camera, scanning everything, from walls and doors to roof and chimneys.

Project leader Michael Rogers, a physics professor, says the camera replaces a whole team of conservators.

“What we do is scan from inside each room from two places so that we get full coverage of the room," he said. "And, then from outside, we’ll scan from... with this building we'll probably do about 12 different positions around the house."

Rogers says no matter where the camera stands, all scanned points take the same position in the coordinate system established for the building. Software calculates those positions and creates a so-called “point cloud,” a 3-D picture of the building made of millions of points about five millimeters apart. The picture can be observed from any direction, inside or outside.

This enables researchers to zoom in and take precise measurements.

Lincoln’s Cottage preservation manager Jeffrey Larry says it is a great way to undertake preservation projects.

“We could go into a certain room and pick out any sort of architectural feature, and then have a record of the changes of that feature or the history of that feature, whatever it may be," he said.

The project is funded by Ithaca College. Rogers says he and his team are still learning what can be done with the $95,000 camera.

“So for me what’s really interesting about the project with where we are now is more about how to use the scanner on a facility like this, how do we do it efficiently, how do we move through the building, how do we make sure we scan all the spaces that need to be scanned," he said.

Rogers says members of his team are eager to find out what kind of data they will be able to extrapolate from such a detailed scan.