Residential schools: The science of searches

What is ground-penetrating radar (GPR)?

GPR is a technology that uses radio waves to capture subsurface images. Similar to a lawnmower in appearance, the wheeled machine can be used to collect data from soil, concrete and debris, among other substances.

How is it used?

GPR can be used in a variety of contexts, including to locate buried utilities such as pipes and cables, in forensic investigations, in archeological digs and to measure snow thickness at ski hills. Images displayed on the screen require interpretation from a professional in the field.

Archeologist Paul Racher said GPR is typically used as a supplement to other archeological methods.

It's a really interesting technology," he said. The data is extremely difficult to read and we try to be very careful with it."

What does it cost?

Many factors influence the cost of a GPR search, including terrain. Racher said it is extremely challenging in forested environments." Clay can also pose a challenge. But the survey, he said, is the easy part.

The technology is designed to detect anomalies" underground, but the data has to be interpreted and confirmed. All said and done, GPR could cost an estimated $20,000 per acre in Ontario.

To put that in perspective, the footprint of the original Mohawk Institute property is 350 acres - which adds up to roughly $7 million to search the grounds.

Kate McCullough is a Hamilton-based reporter covering education at The Spectator. Reach her via email: kmccullough@thespec.com