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Classification of Triangulation System

By: Haseeb Jamal / On: Mar 29, 2017 / Notes, Types of
 
 

Classification of Triangulation System

Triangulation system may be classified according to

  1. Degree of accuracy required
  2. Magnitude of work

Primary or 1st order Triangulation:

In primary triangulation very large areas (such as the whole country) are covered and the highest possible precision is secured. Well proportioned triangles, most refined instrument and methods of observations and computation are used.

Average triangle closure = 1 second

	Max triangle closure = 3 second

	Length of baseline = 5 to 20 km or more (3-10 miles)

	Length of sides of triangle = 30 to 100 km or more (20-100 miles)

	Degree of Accuracy = 1 in 500,000

	Check on the base  = 1 in 25000.

Secondary or 2nd Order Triangulation

Within the primary triangles other points are fixed at closure intervals so as to form a secondary series of triangles. Which are comparatively small Delta Dash S are used, the instars and methods are not of the same at most refined.

Average triangle closure = 3sec
Max = 8 sec
= 2 to 5km [ 1-3 miles]
= 8 to 70 km [ 5-40 miles]

Degree of Accuracy = 1 in 50,000

Check on the base = 1 in 10,000

Tertiary or 3rd order Triangulation

Within the secondary &delta Delta Dash S points are established at short intervals to furnish horizontal control fro detail survey.

Average Delta Dash S closure = 6 sec = 12 sec = 1 to 30 km [½ to ½] = 1.5 to 10 km [less then a mile to 60 miles] Degree of accuracy = 71 in 500 C Check on base = 1 in 500

 

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