Trotter and Associates of St. Charles, Illinois, under contract with the GIS Division, installed 28 permanent benchmarks throughout the City in the Spring of 2008. This included three survey level runs; the first along the west side of the Fox River from Geneva to Elgin, the second on the east side of the City and the third on the west. All three comply with bluebooking requirements established by the National Geodetic Survey (NGS) for vertical measurements and are classified as 2nd Order Class II benchmarks. The first run was submitted to the NGS for inclusion, and once again connects the cities in the Fox River Valley in the Federal Register.
For NGS acceptance a survey level run needs to tie into two existing 2nd Order Class II (or better) benchmarks both at the beginning and end of the run. To perform the survey, Trotter and Associates used a calibrated invar rod, certified by the Laboratory of Meteorology at LAVAL University, Canada to traverse the route and utilized survey grade GPS technologies to capture the horizontal measurement. When appropriate, the control network was adjusted to incorporate existing horizontal Kane County Department of Transportation monuments to create a full 3 dimensional control station.
Each benchmark was driven into the ground until refusal and capped with a 3 1/4" domed cap with a magnet stamped with “City of St Charles Survey Benchmark”. It is enclosed in a 4 inch PVC tube capped with a standard monument access panel.
