Another Magnetometer survey?

We are going to do another magnetometer scan of the river this Friday. Karl Butler (UNB) offered a couple of his students to help scan the third span of the bridge. Last time (April 6, 2003) we had scanned the second one (wrong one) and what we detected then was a rail. This time we will scan the entire width of the river by means of my canoe and a magnetometer which will be tied in to a precision GPS receiver.