Surveying
In triangulation surveys

All listed here
Control stations are located from which detailed surveys are carried out
Sides are not measured excepting the base line
The area is divided into triangular figures

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

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

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