Lasers scan Statue of Liberty

17 Jun 2002

The first accurate maps of the exterior surface of the Statue of Liberty have been released by US scientists.

Using LIDAR, scientists from Texas Tech University, US, have generated the first accurate maps of the exterior surface of the Statue of Liberty. The maps will aid the conservation and maintenance of the monument.

Elizabeth Louden, one of three principle investigators from Texas Tech explains: "Our research group has focused on the adaptation of the laser-scanning technology to use on historic buildings, sites and monuments. With higher resolution, we can analyze the copper deterioration looking for oxidation holes in the surface."

The team uses a Cyrax 2500 system from Cyra Technologies, US. This comprises a frequency-doubled Nd:YAG laser emitting 0.2 mJ pulses of duration 250 ps at a wavelength of 532 nm.

Starting from 13 locations around the statue, Louden and colleagues have acquired in excess of 94 million data points. "Then we successfully merged this data to create a three dimensional model of the areas we have scanned," she said.

The team has now mapped about 60% of the statue's surface by scanning in columns and maintaining a statue-to-laser distance of 100 m at all times. The resulting maps have an accuracy of better than 0.25 inches.

Problem areas include the torch and raised arm where the wind buffeted the target causing it to sway and results to be blurred. Louden says that the top of the head and the feet are also unrecorded, but she hopes to raise further funding to complete the scanning.

Upcoming projects include scanning of the Carlsbad caverns and the Chaco canyon, both in New Mexico, and the Sabine Pass lighthouse in Louisiana.

Author
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.