Calibration of EDMI and recommendations for a base line network in Virginia

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Virginia Polytechnic Institute and State University

Three systematic instrumental errors exist in electronic distance measuring instruments (EDMI): 1) scale error, 2) constant offset error, and 3) cyclic error. The potential magnitude of these errors requires that each EDMI should be calibrated for all three errors. The calibration constants of EDMI may be monitored on an arbitrary base line; however, a calibrated base line is required to perform an accurate EDMI calibration for constant offset and scale errors. Calibration of cyclic error requires monumentation not normally found on a calibration base line. Cyclic error can be measured on a short base line in the laboratory.

The surveyors in the State of Virginia would benefit from a statewide network of calibrated base lines. A network covering the state would provide convenient access for the state's surveyors. A unified network of base lines would give the states surveyors a standard of comparison for their EDMI. This standard of comparison would be nationwide if Virginia would choose the National Geodetic Survey (NGS) to calibrate the base lines in its network. Base line calibration by NGS would require that the state abide by NGS specifications for establishing its base line network.