Once we had two validated benchmarks we ran from the

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Once, we had two “validated” benchmarks, we ran from the nearest validated bench to the CGPS, along the nearest and flattest route available. As per the CSRC specifications (Appendix A), we used drive pins as temporary bench marks along any route that was more than 3 km to the CGPS to break the run into “sections” of less than 3 km. At the Version 1.10 (October 28, 2004) Page 13 of 36 6/14/2018 2:20 AM Table No. 1 Sample Benchmark Elevation Checks/Verification CGPS FROM TO HT DIFF (m) DIST (km) NAVD88 Diff LVL_DH Corrected Diff MAX Allowed Misclosure Single Run Misclosure Double Run Misclosure BKAP FT1138 FT0056 -2.4992 1479 -2.501 -2.501 0.010 0.002 BSRY EV0028 EV0027 -2.9437 206 -2.940 -2.939 0.004 -0.005 EV0027 EV0028 2.9434 206 2.940 2.939 0.004 0.004 -0.0003 EV0027 EV0044 5.8967 1139 5.895 5.897 0.009 0.000 BVPP FU2195 FU2197 -1.9412 85 -1.935 -1.935 0.002 -0.006 FU2197 FU2195 1.9403 85 1.935 1.935 0.002 0.005 -0.0008 FU2195 FU3245 25.7484 1305 25.771 25.771 0.009 -0.023 FU3245 FU2195 -25.7493 1303 -25.771 -25.771 0.009 0.022 -0.0009 FU2191 FU3245 -22.2549 906 -22.259 -22.259 0.008 0.004 CCCC FT0640 FT0638 -16.8391 1566 -16.842 -16.837 0.010 -0.002 COPR EW3794 EW3793 -17.9157 1393 -17.920 -17.920 0.009 0.004 EW3793 AE4854 -2.6773 981 -37.348 N/A 0.008 34.671 AE4854 EW3793 2.6766 978 37.348 N/A 0.008 -34.671 -0.0007 CRBT FV0260 FV0203 -9.0498 1614 -9.048 -9.048 0.010 -0.002
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CGPS, we used a small stainless steel ruler graduated in millimeters (Westcott 10414) as the last rod shot to the ARD point on the CGPS tripod leg. After turning into the CGPS, we ran back from the CGPS to the starting bench along the same route, using the same specs, and across the same temporary benchmarks. The forward run was compared to the return run to assure that we again matched the specified tolerance of 8 mm times the square root of the kilometers. In all cases our results matched well within the allowable tolerance (see Table No. 2 for example). Table No. 2. Double Run Closures from Validated Benchmarks to CGPS ARD. CGPS SITE FROM TO Height Difference (m) Single Run Distance (m) Double Run Closure Maximum Allowable Closure BKAP FT1138 BKAP ARD -1.31269 1137 BKAP ARD FT1138 1.31135 1134 -0.001 0.009 BSRY EV0044 BSRY ARD -2.45185 1193 BSRY ARD EV0044 2.45104 1193 -0.001 0.009 BVPP FU2197 BVPP ARD -69.28625 8698 BVPP ARD FU2197 69.29930 8695 0.013 0.024 CCCC FT0638 CCCC ARD -82.62379 3661 CCCC ARD FT0638 82.62162 3656 -0.002 0.015 COPR EW3793 COPR ARD -15.02212 3793 COPR ARD EW3793 15.02446 3790 0.002 0.016 CRBT EV0260 CRBT ARD 53.40328 1310 CRBT ARD EV0260 -53.40316 1309 0.000 0.009 Office Procedures As the field leveling was completed to each site, the raw data file was downloaded from the level using the proprietary download software. The raw field data was reviewed for quality control and processed to perform a preliminary adjustment of the data. After the preliminary analysis and quality control was complete, preparation of files for submittal to NGS for publication of the elevations were completed. Several programs were used for the handling of the leveling data. In addition to the proprietary download program (that usually comes with the purchase of the level), a program called StarNetPro was used to process the raw data file and adjust the extracted elevation differences. A program called NABOOK was used to create a field book file that was used to find errors and data that did not meet specifications. (Be aware that the program may incorrectly flag standard deviation, as standard deviation of the mean.) This program also is used to create some of the files needed for the NGS publication process.
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