U. S. Geological Survey
Bench Mark

"COPPER NAIL/WASHER"
1934

Jerry Penry
April 20, 2005

The copper nail and washer markers used by the United States Geological Survey were secondary points that were placed between the permanent bench mark locations. The use of these markers first occurred sometime between the 1900-10 era. The copper nail shown below was placed in a wooden bridge timber abutment near Beaver Crossing, Nebraska. If the surveyors discovered an error in running their level loops, they could go back to one of these secondary points in an effort to isolate the problem without having to completely relevel between the permanent bench marks. These marks are rarely found.

The copper nail and washer was placed in a semi-permanent location.

The stability of these markers was likely questionable as time progressed.

This view shows the thickness of the copper washer.

Close-up of the copper nail with copper washer.

The copper nail and washer is shown in this diagram showing the USGS markers being used in 1909.

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© Jerry Penry 2010