Surveying
The hour angle of the heavenly body for Greenwich meridian equals the hour angle of the body for any other meridian + longitude:

Vernal equinox
True sun
Mean sun
All listed here

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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
All listed here
Geodetic triangulation of greatest possible sides and accuracy is carried out
Primary triangles are broken down into secondary triangles of somewhat lesser accuracy

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