THE EFFECTS OF ECCENTRICITY AND MISPLACED INDICES OF DIVIDED CIRCLES

Abstract

Special precautions are taken in the workshop to ensure that divided circles are so mounted that the point from which the circle graduations radiate lies accurately on the axis about which rotation of the circle and reading index or indices takes place. If, through some accident, eccentricity is present, it is still possible to obtain accurate readings if the instrument is used to the best advantage, and the object of the following notes is to assist the surveyor to this end. It will be found that errors arising from eccentricity can be made to cancel out, except in the case of a vertical circle fitted with a single reading index.