Surveying
Which of the following errors can be eliminated by taking mean of bot face observations ?

error due to imperfect adjustment of plate levels
error due to line of collimation not being perpendicular to horizontal axis
error due to imperfect graduations
error due to eccentricity of verniers

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Surveying
For mapping any country

Geodetic triangulation of greatest possible sides and accuracy is carried out
Secondary triangles are further broken into third and fourth order triangles, the points of which are used for detail surveys
All listed here
Primary triangles are broken down into secondary triangles of somewhat lesser accuracy

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