Testing of Measuring Tapes at the Bureau of Standards"The testing of the steel tapes used by the engineer and surveyor is done at the Bureau of Standards by comparison with a steel bench standard described in this paper. For the test of base-line tapes (usually made of invar with a length of 50 m) a much more elaborate apparatus is employed. This geodetic comparator is also described in detail. Results have shown that the length of 50 m invar base-line tapes can be determined with this apparatus to an accuracy such that the absolute errors of the certified result do not exceed 1 part in 1,000,000. |
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____41_ 10-foot point 3000.0 Level Corrections 50 m base 50 m points 50 m tape absolute error alignment plugs apparatus base-line tape bench standard BUREAU OF STANDARDS C.O.Intervals calibrated spring balance CIRCULAR Coast and Geodetic coefficient of expansion COMPARISON OF TAPES Correction to Length cross section designed distance end microscopes foot points geodetic comparator Geodetic Survey geodetic tape holding cut-off cylinder ice load iced bar interval invar Left Mic Length of Comparator Length of Tape length supported throughout longer when supported loops micrometer represents Microns millimeter mounted neutral surface piers precision pulley Readings on Tape Right Mic shown in Figure specified sphere spirit level steel tapes supports at 24.0 suspended at points Tape is longer tape supported throughout tape suspended tape when supported testing spring balances thermometers throughout at 24.0 throughout from observations total grade correction transverse graduation mark trough United States Coast upper surfaces vertical Woodward