2 each measurement shall be verified by re measuring

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2. Each measurement shall be verified by re-measuring with a measuring device graduated in feet. Only measurements that have agreement between the metric and foot measurements of one millimeter or less shall be accepted. 3. The field notes shall show and document all GRM measurements. To make the GRM measurements, it is necessary to remove the CGPS radome to provide access to the CGPS antenna adaptor. 4. Under no circumstances remove, adjust, or manipulate the CGPS antenna. Version 1.10 (October 28, 2004) Page 9 of 36 6/14/2018 2:20 AM Figure No. 3. Last turn into ARD is read optically from level (left) to steel rule held at ARD (right) and manually entered into level for recordation in raw data digital file.
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5. Use care in the removal and reinstallation of the CGPS radomes. Prior to removing each radome, note and mark the position of the radome. When the GRM measurements for each CGPS are completed, immediately reinstall the radome in the exact position as originally installed (for instructions, see SCIGN, 1999 b & c). Equipment Used For the differential level measurements necessary for this project the following equipment was used: Leica NA3003 Digital Level, SN 91716 with recent service record Leica Invar Geodetic 3 Meter Leveling Staff GPCL3, SN 22962 with calibration certificate Leica Invar Geodetic 3 Meter Leveling Staff GPCL3, SN 23219 with calibration certificate In addition to the above major equipment, both rods were equipped with stays, to hold the rod plumb and stable while being read, and dual level bubbles to assure that neither bubble had become out of level during the survey. Kern leveling turtles (pucks) were utilized for solid, stable, but portable, turning points. The same equipment was used during the entire project (see Figure No. 5 for example). Specification and Equipment Issues during Initial Field Work and Office Processing Once field leveling started, we realized we apparently weren’t meeting the specification criteria of 0.1mm standard deviation for each measurement. To achieve a value of 0.1mm for a measurement, we had to use sight lengths of 25 – 30m, even though the FGCS specifications allow a much longer sight length for Second Order, Class II. It was unclear in the FGCS specifications if this was to be 0.1mm standard deviation of “a reading” ( ( r 2 /(n-1))) or of the “mean of three readings” (standard deviation of the mean = Version 1.10 (October 28, 2004) Page 10 of 36 6/14/2018 2:20 AM Figure No. 4. Manual measurement from ARD to bottom of antenna adaptor (left) and from bottom of antenna adaptor to BPA (right).
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Figure No. 5. Leveling equipment used – Leica NA3003, Invar staffs with stays, stiff leg tripod. m / n). It was also unclear at first what was being recorded in the Leica digital leveling file. We called both NGS and Leica to get verification of what we were trying to achieve and what we were achieving, respectively. We got a final determination from the NGS that this specification is supposed to be the standard deviation of the mean even though the FGCS document (1994 version) is not clear on this. From Leica we got
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