Surveying
Homologous points are

Plumb points of stereo pair of photographs
Opposite corners of a photograph
Corresponding points on the ground and photograph
Nodal points of the camera lens

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Surveying
For mapping any country

All listed here
Secondary triangles are further broken into third and fourth order triangles, the points of which are used for detail surveys
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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