Brief explanation on classification of triangulation.

1. By
Alyasah
2ab14cv004

2. Triangulation
 Method of determining distance based on the
principles of geometry.
 A distant object is sighted from two well-separated
locations.
 The distance between the two locations and the
angle between the line joining them and the line to
the distant object are all that are necessary to
ascertain the object's distance.

4. Classification of triangulation
1. First order or primary triangulation
2. Second order or secondary triangulation
3. Third order or tertiary triangulation

5. Primary triangulation
 It is the highest order and is employed either to
determine the earth figure or to give the most precise
control points to which secondary triangulation may
be connected.
 Primary triangulation usually cover large area.

6. General specification
 Average triangle enclosure: less than 1 sec
 Maximum triangle enclosure: Not more than 3 sec
 Length of the base line : 5-10 km
 Length of sides of triangulation: 30-150 km
 Actual error of base: 1 in 300000
 Portable error of base: 1 in 1000000
 Discrepancy between 2 measure of a sector: 10 mm
 Probable error of compacted diameter: 1 in 60000 to 1
in 250000
 Probable error on astronomical azimuth: 0.5 sec

7. Secondary triangulation
 This triangulation system consist of number of point
within the framework of primary triangulation.
 The station are fixed at closed interval. So that the
size of the triangle form are smaller than the primary
triangulation.
 The instruments and method used are not of the same
at most refinment.

8. General specification
 Average triangle enclosure: 3 sec
 Maximum triangle enclosure: 8 sec
 Length of baseline: 1.5 to 5 km
 Length of side of triangle: 8- 65 km
 Actual error of base: 1 in 150000
 Portable error of base: 1 in 500000
 Discrepancy between 2 measure of sector: 20 mm
 Probable error of compacted distance: 1 in 20000 to 1
in 50000
 Probable error in astronomical azimuth: 2 sec

9. Tertiary triangulation
 This system consist of a number of points fixed within
the framework of secondary triangulation and it forms
the intermediate control for detailed engineering and
other surveys.
 Sizes of triangle are small and instrument with
moderate precision may be adopted.

10. General specification
 Average triangle enclosure: 6 sec
 Maximum triangle enclosure: 12 sec
 Length of base line: 0.5 to 3 km
 Length of side of triangle: 1.5 to 10 km
 Actual error of base: 1 in 75000
 Portable error of base: 1 in 250000
 Probable error of computed distance: 1 in 5000 to 1 in
20000
 Probable error in the astronomical azimuth: 5 sec

11. Thank you