Definition
A survey line's deflection angle is the angle it makes with the extension of the preceding line.
Angles of deflection range from 00 to 1800, but they never go above 1800.
The angle of deflection Right deflection angle is the length of the survey line measured clockwise.
The left deflection angle refers to the deflection angle measured counterclockwise from an extended survey line.
Procedure-
- Place the theodolite at Q and precisely level it.
- The Vernier A reading 3600 take backside on p with both plates clamped (i.e. bisect ranging rod at exactly)
- To point the line of sight created by PQ, transit the telescope.
- Lose the top plate and turn the telescope in an R-shaped motion to take the front side. The approximate value of the deflection angle at Q is obtained from the mean of two Vernier readings.
- The Vernier will read the same reading as in the preceding step, and the telescope will be inverted if you release the lower clamp and turn the telescope horizontally to Backsight on P.
- To bisect R more, read Vernier and transit the telescope unclamped the plate. Calculate the final Vernier reading's mean.
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To measure deflection angle with the theodolite
Theory
The angle made by the survey line to the extension of the preceding line is referred to as the deflection angle.Instrument required
- Theodolite
- Ranging rods
Diagram
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Procedure
1. At station 'O,' the instrument was set up and levelled precisely.2. Both plates were clamped at the "O" level, and a station point was used to take the back sight.
3. The upper plot was secured, and station "O's" front view was taken. Both verniers' readings were recorded.
4. The upper plot was secured, and station "O's" front view was taken. Both verniers' readings were recorded.
5. Repeating the procedure, the instruments were once more sighted to "Q." Both verneirs' readings are documented.
6. Since both faces were read, the deflection angle was doubled. By dividing the final reading by 2, it was possible to determine the average deflection angle value.
What is the Angle of Deflection
A deflection angle is typically between a moving object's initial course and departure path. Moreover, this definition differs slightly in disciplines like surveying, photogrammetry, and gunnery. It still revolves around calculating the relative angle between directions, though. Refraction occurs, for instance, when light travels from one medium to another, such as from air through a prism and back to air. At the air-prism interface, the incident ray thus modifies direction. The emergent ray also undergoes another direction change at the prism-air interface. When determining the refractive index of the prism, the angle of deflection (α) between the incident and emergent rays is crucial.
In gunnery, the deflection angle is crucial. In this context, it alludes to the angle formed by the lines of sight to the aiming point and a moving target. A fighter jet, for example, uses the angle's value to lay ahead of a target and give the weapon's precise time of flight to strike the target. These jets move so quickly that the angles are frequently very small, typically measured in milli radians.
The angle of the Deflection Formula
The application at hand heavily influences the angle of deflection formula. When it passes through a prism, the angle of deflection () of light depends on several factors. Additionally, as the ray enters the prism, these parameters include the angle of incidence (1) and the angle of refraction (1). Further, as the beam leaves the prism, it is influenced by the angles of incidence (2) and refraction (2)
A deflection angle is measured between a new line and the prior one in bearing applications. It has a positive value if this angle is measured counterclockwise. Convention dictates that a negative value must be given counterclockwise when the measurement is done.
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Application in Surveying
