Doing a survey and need section monuments for tie out. Searching for two section corners with county corner records in hand, both with 3? county caps. Already had GPS coordinate on one from previous survey work and a bearing distance between them from a filed survey by another surveyor. Both monuments are in the pavement of a highway. So I go to the one I've visited before and find it measures within 0.04 feet of my GPS coordinate (OPUS/RTK about 10 years ago ?? State VRS today). OK good, the other should be easy to find from the bearing and distance from the other survey. Drive down the highway a mile. Smooth pavement, navigate to my search coordinate, break out the mag detector get a good buzz about a foot from my search point. Chisel down about 2 inches and find the top of a 5/8 rebar. OK, doesn't seem right as corner record says a county brass cap. Grab the detector and 1.3 feet away get another good signal about 0.5 feet away from search coordinate and 1.3 feet away from the rebar. Chisel down again a couple inches and find the brass cap. At least it wasn't a pair of vise grips or something. It did make two holes in the pavement. Makes me wonder if the surveyors that set the county cap about 15 years ago using proportion searched with a detector before they set the county cap. The original corner would have been a wood post set in 1856 by the GLO. The highway was at last 5 feet of fill at this location. The markers did line up with an old fence line going south, the rebar better than the county cap.
You never know what kind of magnetic material you are going to buzz up. The ones that irritate me most are magnetic stones, except for one I found about 1-1//2 feet deep with a 1/4 cut in a few years back.
Speak of irritation - Much of Central Oregon is covered with basalt pressure ridges, basalt ledges, and strewn about with surface and subsurface basalt
rocks, much of which has a high iron content.?ÿ Makes searching with a mag. locator tons o' fun!