Surveying
The latitude of the observer's position, is

Angular distance along the observer's meridian between equator and the observer
Declination of the observer's zenith
Elevation of the elevated pole
All listed here

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Surveying
The error due to eccentricity of inner and outer axes can be eliminated by

taking both face observations and taking the mean of the two
double sighting
taking mean of several readings distributed over different portions of the graduated circle
reading both verniers and taking the mean of the two

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