What is angular measurement in surveying?

Short Answer:

Angular measurement in surveying is the process of finding the angle between two lines or directions from a common point. It helps in determining the direction, slope, and layout of land areas. Angles are usually measured in degrees, minutes, and seconds using special instruments.

This measurement is very important for preparing accurate maps, setting out curves, and calculating land boundaries. Instruments like theodolites, compasses, and total stations are commonly used for angular measurement in different types of surveys.

Detailed Explanation:

Angular measurement in surveying

Angular measurement in surveying means finding the angle formed between two lines or directions that meet at a single point, which is usually the instrument station. It is a very important step in all kinds of surveys, especially when creating maps, laying out roads, or measuring land areas. These angles help to determine how far and in which direction a particular point lies from another.

There are two types of angles used in surveying – horizontal angles and vertical angles.

  • Horizontal angles are measured in the horizontal plane, usually between two lines or objects at the same elevation. These are commonly used in land and boundary surveys.
  • Vertical angles are measured in the vertical plane, used for determining the elevation or height of an object above or below the horizontal line of sight. These are useful in topographical and construction surveys.

The unit of measurement for angles is degrees (°), minutes (′), and seconds (″). A full circle is 360 degrees. Each degree has 60 minutes, and each minute has 60 seconds. This fine division allows very accurate angular readings, which is essential for precise land measurement.

Surveyors use instruments like the compass, theodolite, and total station to measure angles:

  • A compass helps in measuring angles with reference to the magnetic north. It is mostly used in rough and quick surveys.
  • A theodolite is more accurate and is used for both horizontal and vertical angle measurement. It consists of a telescope mounted on a base that can rotate both vertically and horizontally.
  • A total station combines the functions of theodolite and electronic distance measurement (EDM). It measures angles and distances digitally and stores the data electronically.

The procedure generally starts by setting up the instrument at a known point and leveling it properly. Then the surveyor sights a known back point and sets the horizontal angle to zero. The instrument is then rotated to sight the forward point, and the angle between the two lines is read. This process can be repeated for multiple points around a station.

Angular measurements are used for:

  • Triangulation surveys
  • Calculating area and layout
  • Setting out curves in roads and railways
  • Finding height differences using vertical angles
  • Navigating and preparing maps

Accuracy in angular measurement is crucial because even a small mistake in angle can lead to a large error in the final survey results. That is why theodolites and total stations are preferred for most important surveys, as they offer high precision.

Conclusion:

Angular measurement in surveying is the method of finding the direction and relative position of points by measuring angles. It plays a key role in producing accurate maps, layout planning, and construction work. Using proper instruments and careful measurement ensures better quality and precision in any survey.