Mapping tech helps grim search

U.S. Geological Survey mapping technology is helping searchers look for the remains of Xiana Fairchild, a California girl who disappeared in December 1999 at age 7.

Last week, DNA tests identified a skull found in January as Xiana's. Investigators are using USGS digitized photographic maps with resolution of up to 1 meter to help them search the area around the site where the skull was found — in Los Gatos, between San Francisco and San Jose — for the rest of her remains.

A geographic information systems specialist working with the Santa Clara County Sheriff's Department initially downloaded a digital orthophoto quadrangle (DOQ) from USGS. A DOQ is an aerial photograph that's been scanned and has had distortions corrected so that it can be used as a map.

The DOQ was based on aerial photographs taken in 1993, and the GIS specialist contacted USGS to see if the agency could provide more recent images of the search area, said Dale Russell, a program manager for the USGS in Menlo Park, Calif.

USGS technicians at the agency's Earth Resource Observation Systems (EROS) Data Center in Sioux Falls, S.D., found a negative of a photograph of the area taken in 1999. They scanned the 9-inch by 9-inch negative, rectified it for mapping and posted the resulting DOQ file on a FTP site. The GIS specialist then downloaded the file to his laptop computer.

"They were able to do that within a couple of hours of his request," Russell said.

Law enforcement officials wanted the newer images to help them identify locations where the killer may have left Xiana's body, Russell said. The newer DOQ shows where new roads and turn-offs have been built and where vegetation has grown, he said. Officials can zoom in to an area of 100 feet by 100 feet. At such a resolution, objects as small as 1 meter wide, such as a garbage can, can be seen, he said.

The photographs are taken at an altitude of 20,000 feet, Russell said. Under USGS' National Aerial Photography Program, contractors flying on behalf of the agency photograph the entire United States, and an area is rephotographed about every five years, Russell said.

According to Russell, the agency's topographic maps and DOQs are used routinely in emergencies, including last year's forest fires in New Mexico and the Midwest floods in 1993.

Xiana, of Vallejo, Calif., had been missing since Dec. 9, 1999, when she left her house to walk to a nearby school bus stop, according to the Contra Costa Times. The newspaper reported Tuesday that the search for the girl's remains has been suspended indefinitely, but that police plan to resume searching at a later time. Police are also investigating a prison inmate's claims that he is responsible for her death.