The Constructor

What is Triangulation Surveying? Operations, Applications and Advantages

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What is Triangulation Surveying?

Triangulation surveying is the tracing and measurement of a series or network of triangles to determine distances and relative positions of points spread over an area, by measuring the length of one side of each triangle and deducing its angles and length of other two sides by observation from this baseline. Triangulation surveying was first introduced by a Dutch man named Sneli. Triangulation is preferred for hills and undulating areas, since it is easy to establish stations at reasonable distances apart, with intervisibility. In plane and crowded areas it is not suitable as the intervisibility of stations is affected. The difficulty is overcome by building towers which is quite expensive. The main disadvantage of triangulation is the accumulation of error in the lengths and direction of lines, since both of them, for successive lines, depend upon the computations for those of the preceding line, which necessitates the check bases. In triangulation, entire area to be surveyed is covered with a framework of triangles. For the triangle, the length of the first line, which is measured precisely is known as Base line. The other two Computed sides are used as new baselines for two other triangles interconnected with the first triangle. By extending this process, a chain or network of triangles can be spread over the entire area.

Operations in Triangulation Survey

The field work of a triangulation is carried out in the following well defined operations: Besides field work, triangulation consists of the specifications, the design of stations and signals, and the reduction and adjustment of the observations.

Applications of Triangulation Surveying

Triangulation Systems

A system consisting of triangulation stations connected by a chain of triangles. The complete fig is called triangulation system or triangulation figure. The most common type of figures used in a triangulation system are Geometric conditions to be fulfilled by above figures in triangulation system are: It is impossible to fulfil all the geometric conditions, owing to the errors, until the field measurements have been adjusted.

Triangles

1. A chain of triangles is very rapid and economical when a narrow strip of terrain is to be surveyed. 2. Angles less than 30o or more than 120o are not permitted 3. For well-conditioned triangles, angles should not be less than 30o or more than 120o. Advantages of triangles: Disadvantages:

Quadrilaterals

  1. These afford an excellent system since the various combinations of sides and angles can be used to compute the lengths of required sides, and checks can be made frequently
  2. The best quadrilateral is square. A quadrilateral with both diagonals having no station at their intersection is usually employed.
  3. This is best suited for hilly areas.
Advantages

Polygons

1. When areas that are very wide in proportion to their lengths are to be surveyed then pentagonal or hexagonal figures may be economical. 2. These may or may not have a central station. Advantages
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