6 maximum difference between forward and backward

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6. Maximum difference between forward and backward running of the double run lines not to exceed 8mm times the square root of the shortest one way length of section in kilometers. 7. Maximum difference between record elevation difference and single run difference to verification bench to also be less than 8mm times the square root of the shortest one way length of section in kilometers. If first run between benches does not pass, run back to the initial bench. If your two runs match each other to the above spec but still do not match the record, you must run to further benches. 8. If any runs/sections are more than 3 kilometers, set a drive pin as a temporary bench to make sections 3 km or less in length, in order to isolate any errors and minimize the amount of reruns necessary to correct any errors. 9. The last turn into the ARD will have to be made with the “A” Rod on the turning puck and the stainless steel 6” ruler read with the optical cross hair and hand entered into the gun. Make this a short turn with about a 5-10 meter sight distance (far enough away to focus, but as close as possible to negate any inaccuracies in the optical reading) (see Figure No. 3).Turning back out from the ARD would be just the opposite of the above. 10. For verification of the benchmark elevations in the field, it is a good idea to have previously run the planned benchmarks through the NGS program LVL_DH (Shields, Version 1.10 (October 28, 2004) Page 8 of 36 6/14/2018 2:20 AM
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2003), to determine the elevation difference that takes the gravity correction out of the published difference to give a difference that should match raw leveling. This is the difference that we are trying to match. 11. Review guidelines for NGS project submittals regarding field raw data file. There are specific guidelines for recording the temperatures at the beginning and end of a section, the instrument person, the time of leveling, etc. Also the curvature function should be turned off in the level and the data should be collected in meters. Appendix A has some of this information, with additional references to help determine the correct field data file collection methods. 12. A unique identifier should be assigned to each mark to be elevated. The last four numbers of the NGS PID could possibly be utilized for the BM’s. Other marks should be identified so to avoid identical numbers in other sections of the leveling project. Radome removal and BPA measurement training 1. At each CGPS, measure two vertical distances – a) from the reference mark on the CGPS leg to the bottom of the CGPS antenna adaptor and b) from the bottom of the adaptor to the top of the adaptor – all in accordance with CSRC procedures. The vertical distance from the bottom to the top of the adaptor shall be the average of four measurements at different locations, approximately 90 degrees apart, around the adaptor. All measurements shall be made to the nearest millimeter and shall be accurate to plus or minus one millimeter.
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