Principles of Triangulation in Surveying

Triangulation: Principles

• A method for determining the precise location of points by measuring angles between them.
• Based on the principle of geometric relationships between angles and sides of triangles.
• Essential for accurate surveying and mapping.

Classification of Triangulation Systems

• Primary Triangulation: Establishes a network of control points with high accuracy, covering large areas.
• Secondary Triangulation: Densifies the primary network, providing control points for more detailed surveys.
• Tertiary Triangulation: Further densifies the network, providing control points for local surveys.

Triangulation Figures

• Triangles: Basic building blocks of a triangulation system, determined by measuring three angles.
• Quadrilaterals: Four points connected by four sides, providing redundancy and improved accuracy.
• Polygons: Figures with more than four sides, offering greater flexibility and coverage.

Station Choice

• Visibility: Stations should have clear lines of sight to other stations.
• Accessibility: Stations should be readily accessible for setup and measurement.
• Stability: Stations should be located on stable ground to minimize movement.

Phases of Signals

• Day Signals: Used during daylight hours, often made of white flags.
• Night Signals: Used during nighttime, employing electric lamps or other illuminated objects.

Towers

• Types: Steel, wooden, or composite structures.
• Purpose: Elevate signal targets for better visibility.
• Height: Determined by the distance and terrain to ensure visibility.

Satellite Stations

• Purpose: To connect different triangulation networks or establish a network in a remote area.
• Signals: Often transmitted via radio waves or electromagnetic radiation.

Reduction to Center

• Adjustments for measurements taken from a point other than the actual station.
• Corrections applied to observed angles to account for deviations by the instrument.
• Uses calculations based on instrument position, target position, and the distance between the station and the instrument.

Field Work

• Reconnaissance: Conducting a preliminary survey to plan triangulation network.
• Inter-visibility: Ensuring visibility between stations, often achieved through clearing vegetation.

Angular Measurements

• Use of Theodolite: A precise instrument for measuring horizontal and vertical angles.
• Procedures: Utilizing accurate methods like repetition method to minimize measurement errors.
• Targetting: Focusing on signals accurately to ensure precise measurements.

Base Net

• Ground-based measurement: Accurate measurement of a baseline distance using precise instruments.
• Purpose: Provides a starting point for calculating all other distances in the triangulation system.

Extension of Base Net

• Extending the Base Line: Establishing new baselines by connecting existing ones through accurately measured triangles.
• Purpose: To extend the base line to different regions within the triangulation network.