Elizabeth,
David Nobes ([log in to unmask]) may be able to help you.  He's a
geophysicist who's done a lot of work with ground-penetrating radar.  I know
that he's used this technology with graves in New Zealand & I think he may
also have worked on some sites in Canada.  I'm not sure of the exact nature
of the conditions he's worked in, but he may be able to point you in the
right direction.

Katharine