Explain the terms applied to theodolite survey?

1. Theodolite: A theodolite is a precision instrument used in surveying and engineering to measure horizontal and vertical angles. It consists of a telescope mounted on a rotating base, with graduated circles for measuring angles in both horizontal and vertical planes.

2. Horizontal angle: The horizontal angle is the angle measured in the horizontal plane between two points or lines. It is measured using the horizontal circle of the theodolite.

3. Vertical angle: The vertical angle is the angle measured in the vertical plane between a horizontal line and a line of sight to a point. It is measured using the vertical circle of the theodolite.

4. Vernier scale: The vernier scale is a secondary scale on the theodolite that allows for more precise measurement of angles. It is used in conjunction with the main scale to read angles to a higher degree of accuracy.

5. Leveling: Leveling is the process of ensuring that the theodolite is set up and aligned correctly so that measurements are accurate. This involves using a spirit level to ensure that the instrument is horizontal and adjusting the leveling screws as needed.

6. Traversing: Traversing is a surveying technique used to measure the horizontal and vertical angles between a series of points. It involves setting up the theodolite at each point and measuring the angles to determine the direction and distance between the points.

7. Backsight and foresight: In theodolite surveying, the backsight is the first sighting taken on a known point, and the foresight is the second sighting taken on the next point to be measured. The difference in angles between the backsight and foresight is used to calculate the horizontal and vertical angles between the two points.

Horizontal Plane and Vertical Plane:

- Horizontal Plane: The plane perpendicular to the vertical axis of the theodolite.
- Vertical Plane: The plane passing through the vertical axis and the line of sight.

Angles and Directions:

- Horizontal Angle: The angle measured in the horizontal plane between two lines connecting the instrument with points on the ground.
- Vertical Angle: The angle measured in the vertical plane between the line of sight and the horizontal plane.
- Azimuth: The horizontal angle measured clockwise from a reference direction (e.g., true north, magnetic north).
- Bearing: The horizontal angle measured from a specific direction (e.g., a grid line).

Instrument Components:

- Horizontal Circle: The graduated circle mounted on the horizontal axis, used for measuring horizontal angles.
- Vertical Circle: The graduated circle mounted on the vertical axis, used for measuring vertical angles.
- Telescope: The optical device used for viewing and measuring angles.
- Tacheometer: An attachment to the telescope that allows for distance measurements.
- Leveling Screws: Screws used to level the theodolite and bring the vertical axis to the plumb position.

Survey Procedures:

- Setting Up: Positioning and leveling the theodolite over a survey point.
- Sighting: Directing the telescope toward a target point.
- Reading Angles: Reading the horizontal and vertical circles to determine the angles.
- Traversing: A series of measurements taken at multiple points to determine the direction and distance between them.
- Resection: Determining the position of an unknown point by measuring angles from known points.
- Triangulation: Determining the position and height of a point by measuring angles and distances from multiple known points.

Accuracy and Precision:

- Accuracy: The closeness of a measurement to the true value.
- Precision: The consistency of repeated measurements.