BP'ers

I need info on where to purchase a hand-held GPS in the $300 range.
Suddenly came to the realization that in the process of drilling holes
through floors of historic buildings with complex multilayers that it
would be nice to be able to tell where we are drilling in the vertical
plain... like, will this core fall on the Metro North track? Are we
really doing this water test above the electrical switch gear for the
hotel? I'm told the cable guy uses these things now, as well as the
phone installer.

][<en Follett