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How many methods are there for prolongation of a straight line?
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In surveying, the prolongation of a straight line using a theodolite is primarily achieved through three distinct methods: the Back-Sight and Fore-Sight method, the Double-Sight or Double-Reverse method, and the Running-Sight or Intermediate-Sight method.
In surveying, the prolongation of a straight line using a theodolite is primarily achieved through three distinct methods: the Back-Sight and Fore-Sight method, the Double-Sight or Double-Reverse method, and the Running-Sight or Intermediate-Sight method.
EtotalтАЛ=EcollтАЛ+EhorizтАЛ тАФ represents the summation of collimation and horizontal axis errors during prolongation.
The three methods are: 1. The Back-Sight and Fore-Sight method (Standard), which involves plunging the telescope after sighting the back point. 2. The Double-Sight or Double-Reverse method, used to eliminate instrumental errors by performing two sets of readings with the face left and face right. 3. The Running-Sight or Intermediate-Sight method, used when multiple points are needed along the prolongation line where visibility is constrained.
Prolongation is used to extend a survey line beyond existing points.
The Double-Reverse method is the most accurate as it minimizes effects of instrumental errors like non-perpendicularity of the transit axis.
Precise centering and leveling are prerequisites for all three methods.
Enables continuous surveying over long distances.
Reduces cumulative errors when using proper techniques.
Susceptible to errors in centering if not performed meticulously.
Requires professional expertise to minimize index error.
Setting out road alignments.
Railway track alignment and survey.
Large-scale infrastructure layout.
Other methods such as 'swinging the telescope' are sometimes categorized under these three main approaches based on their specific adjustments.
Option B (3) is correct because it covers the standard classification in classic surveying textbooks by authors like Punmia or Arora.
B is correct тАФ There are three standard methods for the prolongation of a straight line using a theodolite: Back-sight/Fore-sight, Double-Reverse, and Running-sight.
Always remember that the Double-Reverse method is the preferred field technique to negate the effect of index error in horizontal or vertical alignment.
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