USE OF TRIANGULATION

Triangulation survey is conducted for one or more of following purposes:

• For establishing accurate ground control points for photogrammetric survey of large area.
• For determining the size and shape of earth by making observations for latitude, longitudinal gravity etc.
• To establish accurate horizontal control of various engineering projects.

Steps followed in Triangulation

Field work

• Reconnaissance
• Establishment and preparation of triangulation stations
• Measurement of base line and check base
• Measurement of horizontal angles

Office work

• Specifications of stations and signals
• Necessary adjustments in observations
• Computations of lengths of sides
• Computations of bearings, latitudes and departures
• Computation of independent co-ordinates

TRIANGULATION SYSTEM

• A system consisting of triangulation stations connected by a chain of triangles is called as triangulation system or triangulation figure.
• Most commonly used figures in triangulation system are:

(a)     Triangles                           (b) Quadrilaterals                      (c) Polygons

All these triangulation figures must satisfy the required geometrical conditions.

• But it is not possible to satisfy all the geometrical conditions due to errors involved in observations and calculations until the field measurements have been adjusted.

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