All design surveys and staking surveys should always be done at surface, that doesn't necessarily mean a scale factor of 1. It does mean that a tape, total station, gps should measure the same distance along the surface of the earth.?ÿ
@tazsurveyor I do work for the concrete contractor. Every year I get to install thousands of sets of anchor bolts of various shapes and sizes, however, this is the first time I've been "forced" to apply a scale factor. I just didn't make a big fuss about it given the small size of the building.
We used a scale factor on the Tappan Zee Bridge aka Mario Cuomo Bridge. The scale was shown on the shop drawings for each longitudinal beam.?ÿ The difference between the grid to the ground for this 3.2-mile bridge amounted to 0.92ft.?ÿ During hot days, the thermal co-efficient for expansion of steel could amount to 0.25" per 1750ft span.
I'm working on a large 500-acre site with three large buildings (700ft). All site is done on State Plane coordinates with GPS no scale, but if done with EDM a scale would be applied. The scale factor on this job would be 0.58ft in?ÿ 10,000ft, and it is inversed. Grid distances are larger than Ground with a CSF of 1.00005829.
We are using BIM coordinate system for all buildings, with no scale factor on EDM. We have four different Survey firms measuring the same anchor bolts. Early on we had differences up to 0.04'. I had to educate the other crews. Some were measuring anchors from 500ft to 1100ft away with S5, then an S6, now an S8 gun. Now we all use the same control, same prism, and measure bolts at the same exact time. Results are now 0.02'.
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@leegreen Same here Lee. We used the same control points, the same prism (Leica Circular prism), the same person holding the prism ( just rotated towards the instrument that was taking the shot), a pole with a 8' bubble and less than 1mm runout and a bipod, but different files, each created independently.
@ramses YES! exactly. I used to do hand drafting for structural steel in another lifetime. There is always adjustment designed into the fabrication.... whether that is slotted openings or site welded plates etc... There is always a gap in the connection design.
