What is Triangulation Surveying?
What is Triangulation Surveying?
Triangulation Surveying is a method of surveying that uses measuring and tracing a series or network of triangles to determine distances and the relative positions of points spread across an area. By measuring the length of one side of each triangle and deducing its angles and length of the other two sides, one can accurately determine the distance and position of points. Triangulation Surveying was first introduced by Dutch surveyor Sneli.
How Does Triangulation Surveying Work?
Triangulation Surveying works by measuring the length of one side of each triangle and then observing the angles and length of the other two sides from the baseline. This allows surveyors to accurately determine the distance and position of points. The observations are then recorded, allowing surveyors to create a detailed map of the area.
Benefits of Triangulation Surveying
Triangulation Surveying is a precise and accurate method of surveying that can provide detailed maps of an area. It is also much easier and faster than traditional methods of surveying, as it requires fewer measurements and observations. This makes it a cost-effective and efficient method of surveying.
Triangulation for Hills and Undulating Areas
Triangulation is the preferred method of surveying for hills and undulating areas, due to the ease of establishing stations at reasonable distances apart with intervisibility. This method is not suitable for plane and crowded areas, however; as the intervisibility of stations is affected. To overcome this difficulty, towers must be built, although this is quite expensive. The main disadvantage of triangulation is the accumulation of errors in the lengths and directions of lines, as both are dependent on the computations for the preceding line, necessitating the use of check bases. To survey an area, a framework of triangles is formed, using the length of the first line, known as the Base line, as the starting point. The other two sides are computed, and then used to form two other triangles that interconnect with the first. By extending this process, a network of triangles can be spread over the entire area.
Operations in Triangulation Survey
Overview of Triangulation
Triangulation is a surveying technique used to accurately determine the location of points on the Earth’s surface. It involves the measurement of angles and distances between points, the specification of stations and signals, and the reduction and adjustment of observations. This technique is commonly used for mapping and navigation.
Reconnaissance
Reconnaissance is the process of gathering information about the terrain and terrain features in the area of interest. This helps determine the best locations for surveying stations and signals.
Station Preparation
Station preparation refers to the setup of surveying equipment, such as theodolites, and the marking of points. This ensures that all points are accurately measured and that the survey results are reliable.
Baseline Measurement
Baseline measurement is the process of measuring the distance between two points. This is done using a variety of techniques, such as triangulation, trilateration, or EDM (electronic distance measurement).
Measurement of Angles
Angles are measured using a theodolite. This instrument is used to measure vertical and horizontal angles between points. The measurements are then used to calculate the distances between points and to triangulate the position of points on the Earth’s surface.
Applications of Triangulation Surveying
Establishing Accurate Control Points for Plane and Geodetic Surveys
Establishing control points for plane and geodetic surveys of large areas requires careful planning and execution. This process involves the use of various survey instruments and methods to accurately determine the positions of control points, which can then be used to accurately map out the area being surveyed. The control points are identified by their coordinates, which are found by using triangulation or trigonometric leveling techniques.
Establishing Accurate Control Points for Aerial Surveying
Establishing accurate control points in connection with aerial surveying involves the use of aerial photography and digital mapping. This process allows surveyors to accurately locate control points with the help of aerial imagery and other surveying techniques. The coordinates of the control points can then be used as reference points for further surveying of the area.
Accurate Location of Engineering Projects
Accurate location of engineering projects such as centre lines, terminal points and shafts for long tunnels, and centre lines and abutments for long span bridges require precision surveying techniques. This involves the accurate location of the engineering projects using survey instruments such as theodolites, total stations, and GPS systems. The coordinates of the control points are then used to accurately locate the engineering projects and map out the area.
Triangulation Systems
What is a Triangulation System?
A triangulation system is a system consisting of triangulation stations connected by a chain of triangles. This complete figure is referred to as a triangulation system or triangulation figure. The most commonly used figures in a triangulation system are triangles, quadrilaterals, and polygons.
Geometric Conditions in a Triangulation System
In order for the triangulation system to be accurate, certain geometric conditions must be fulfilled. These conditions include:
• The sum of interior angles should be (2n-4)x90o, where n = the number of sides of the figure.
• If all the angles are measured at a station, their sum should be 360o.
• The length of sides calculated through more than one route should agree.
Errors in Triangulation Systems
It is impossible to fulfill all the geometric conditions mentioned above due to errors in the field measurements. To ensure accuracy, these field measurements must be adjusted.
Triangles
Paragraph 1:
HEADING: Benefits of Using a Chain of Triangles for Surveying
A chain of triangles is an efficient method for surveying a strip of terrain due to its speed and cost-effectiveness.
Paragraph 2:
HEADING: Limitations of a Chain of Triangles for Surveying
When using a chain of triangles for surveying, angles between 30° and 120° must be used to ensure accuracy.
Paragraph 3:
HEADING: Advantages of Using Well-Conditioned Triangles for Surveying
For well-conditioned triangles, angles of greater than 30° and less than 120° should be used for optimal accuracy.
Advantages of triangles:
- This is simple and rapid
- Economical method
Disadvantages:
What is High Order Triangulation?
High Order Triangulation is a surveying technique used to measure long and narrow strips of land. It involves the use of a series of triangles to accurately measure the length and width of the land being surveyed.
Why is it Necessary to Introduce Base Lines?
In order to reduce the accumulation of errors when surveying a long and narrow strip of land, it is necessary to introduce a number of base lines when using High Order Triangulation. This allows for a more accurate measurement of the land being surveyed.
What is the Least Accurate Method?
The least accurate method of using High Order Triangulation is to use a single chain of triangles. This method is not recommended as it can lead to a high accumulation of errors.
Quadrilaterals
- Paragraph 1: Benefits of Using Quadrilaterals for Computing Lengths
- Using quadrilaterals for computing lengths is an excellent system, providing a range of combinations of sides and angles. This allows for accurate calculations of the lengths of the required sides and for frequent checks of their accuracy.
- Paragraph 2: The Benefits of Using a Square Quadrilateral
- The best quadrilateral for this purpose is a square, as it has four equal sides and four right angles, making it easier to accurately measure and calculate the necessary lengths. Additionally, a quadrilateral with both diagonals having no station at their intersection is often used, particularly in hilly areas.
Advantages
- Most accurate system as the number of checks are more.
Polygons
Paragraph 1:
Surveying Wide Areas with Pentagons or Hexagons
When surveying areas that are very wide in comparison to their length, pentagonal or hexagonal figures may be the most cost-effective shape to use. This method can be used regardless of whether a central station is present or not.
Advantages
- This is also more accurate as the desired number of checks are more.