Volume 11, Number 1 • Spring 2003 • Advanced Technologies

NASA Sharpens Underground Image of World Trade Center Area

Graphic showing underground imaging. Image provided by Witten Technologies.

NASA is applying its image-processing expertise to enhance underground radar images of the area around the World Trade Center, providing a clearer picture of what is beneath the surface.

“Our image-processing techniques will provide the first enhanced subsurface images of the area around ground zero,” said Dr. Amir Fijany, Principal Scientist and Supervisor for the Ultracomputing Technology Research Group at NASA Jet Propulsion Laboratory in Pasadena, CA. “Our goal is to pinpoint utility lines and improve the overall sharpness of the images.”

Witten Technologies, Inc., of Boston, supplied JPL with underground images from lower Manhattan created with ground-penetrating imaging radar in surveys done for Consolidated Edison Company of New York, Inc. (Con Edison), in August 2001 and January 2002.

Witten used a new technique called underground radar tomography, which resembles satellite radar but rides on the back of a truck directly over the site, producing a three-dimensional picture of what’s below the surface to depths of about 1.8 meters (six feet). Those images have already proved valuable in helping reduce the amount of digging needed to maintain dense underground utility networks.

JPL is adding another dimension to the images already collected by Witten by pinpointing linear features such as gas and electrical lines. “We have a continuous underground image below about eight acres of streets in lower Manhattan, including several streets surveyed before and after 9/11,” said Dr. Michael Oristaglio, chief scientist of Witten Technologies. “But some of the most important features are fuzzy; they’re at the limit of resolution of the radar. We are hoping that JPL’s expertise in advanced radar image analysis can bring these features into sharp focus.”

Witten is providing JPL with data from around the World Trade Center area before and after September 11, 2001. “Comparing these two sets of radar images taken from the same area may enable the team to detect underground changes and assess the extent of damage,” said Fijany.

JPL is applying its image-processing and feature-extraction techniques to these images. The primary goal will be to pinpoint semi-continuous linear features that could correspond to buried utility lines such as phone lines, gas lines, pipes or other infrastructure. A secondary goal is to improve the overall sharpness and appearance of the raw image by reducing clutter and enhancing linear features. This initial phase is expected to take six months.

Additionally, JPL will conduct tests on three other sets of images with increasing levels of complexity from other sites in Manhattan taken in February and July 2001.

Fijany led a similar assignment in subsurface imaging to detect unexploded ordnance for the US Army Corps of Engineers. During this assignment, radar data collected by high-altitude airborne ground-penetrating Synthetic Aperture Radar (SAR) was used for subsurface imaging. Advanced image-processing techniques, including novel clutter reduction and feature-extraction algorithms, were then applied to the radar images.

The results from that work showed that this type of remote-sensing technology could detect very small features below the surface. Similar subsurface imaging technology will be applied to the images collected by Witten to enhance their overall quality.

The regional government of Vasterbottens in Sweden, where the ground-penetrating radar technology is manufactured, provided its support to Witten for the additional surveys that were done in January 2002. Additionally, Con Edison is providing Witten additional support for the project through a grant with the Urban Utility Center of Polytechnic University in Brooklyn, NY. Q

For more information, contact Dr. Amir Fijany at NASA Jet Propulsion Laboratory, MS 126-347, 4800 Oak Grove Drive, Pasadena, CA 91109, T: 818/393-5342, F: 818/393-5244, Amir.Fijany@jpl.nasa.gov. Please mention you read about it in Innovation.

NASA Official: Jonathan Root • Web Design: Printing & Design Office, NASA Headquarters • Credits