Surveying
In the double application of principle of reversion, the apparent error is

equal to true error
two times the true error
half the true error
four times the true error

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Surveying
For mapping any country

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

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