Station Uncertainty Analysis

Abstract

Joseph Calkins's paper on evaluating measurement system uncertainty describes measuring an initial system before a survey and re-measuring it afterwards, then comparing the two to recover the uncertainty as found – instrument inaccuracy, drift, measurement error, thermal drift and tooling error all together. Spatial Analyzer does not support that analysis directly. Jeffrey Hammond describes a first step towards it: select the initial and final systems, build a new file holding two copies of the survey, put both into a USMN in which neither instrument may move, and use the resulting unique uncertainty values to overwrite the instrument defaults and re-evaluate every measured point. The purpose is to stop treating drift as a gauge-tolerance judgment call and start treating it as a number.