Principle of Elementary Surveying – SS3 Geography Lesson Note (Second Term)

Surveying is the process of measuring and mapping the Earth’s surface to gather data about the shape, dimensions and features of an area of land. Surveyors use instruments and techniques to determine distances, angles and elevations. The results give accurate representations of terrain for construction, mapping and land development.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Explain surveying terms and describe surveying instruments.
2. State the uses of the chain and the prismatic compass in surveying.
3. Mention the procedures for plotting a traverse.
4. Discuss ways of avoiding obstacles in the field.

Instructional techniques

• Identification
• Explanation
• Questions and answers
• Demonstration
• Videos from the source

Instructional materials

• Videos
• Loudspeaker
• Textbook
• Pictures

What terms and instruments are used in surveying?

Surveying involves several terms and instruments:

1. Total station: A precision instrument used for measuring angles and distances, combining a theodolite and an electronic distance meter.
2. Theodolite: An optical instrument for measuring both horizontal and vertical angles, important for determining precise angles during surveys.
3. Level: Used to determine height differences or elevations between points on the Earth’s surface.
4. GPS (Global Positioning System): A satellite-based navigation system that allows surveyors to determine accurate positions on the Earth’s surface.
5. Chain and tape: Traditional tools for measuring distances on the ground. A chain is a series of connected links, and a tape is a flexible measuring tape.
6. Prism and prism pole: A prism reflects signals to a total station, helping measure distances accurately, while a prism pole holds the prism at a known height.
7. Measuring tape: Simple but effective for measuring distances on the ground. Steel or fibreglass tapes are common.
8. Auto level: An instrument that automatically levels itself, used for determining level points across a surveyed area.
9. Ranging pole: A simple yet essential tool used in surveying and mapping.
10. Benchmark: A point with a precisely known elevation, used as a reference for measuring other elevations in a survey.

What are the uses of the chain and the prismatic compass in surveying?

Uses of the chain

• The chain is used to measure distances on the ground. Chains come in various lengths, and they are stretched between two points to determine the distance.
• Chains are often used in traversing to measure the lengths of survey lines accurately.

Uses of the prismatic compass

1. A prismatic compass is used to measure magnetic bearings or directions. It helps in determining angles with respect to magnetic north.
2. Surveyors use the prismatic compass to establish a reference direction for their survey work.

What are the procedures for plotting a traverse?

Plotting a traverse involves representing surveyed lines and angles on a map or drawing. The following are the general procedures:

1. Select a scale: Choose an appropriate scale for the drawing. The scale gives the relationship between distances on the map and the actual distances on the ground.
2. Draw a baseline: Start by drawing a baseline that represents one of the measured survey lines. This can be a horizontal line along the bottom or another suitable orientation.
3. Plot angles: Use the measured angles from the traverse to plot the direction of the subsequent survey lines. This is typically done using a protractor or compass.
4. Plot distances: Using the chosen scale, measure and mark distances along the plotted lines to represent the lengths of the survey lines.
5. Complete the traverse: Continue plotting the angles and distances until the entire traverse is represented on the map.
6. Check closure: Make sure the traverse forms a closed figure. If it does not, adjustments may be needed to correct errors in measurement or plotting.
7. Label points: Label the points where the survey lines intersect. These points represent survey stations or locations.

What are the ways of avoiding obstacles in the field?

Avoiding obstacles in the field is important for a smooth and accurate surveying process. Below are some ways to achieve this:

1. Pre-survey site visit: Visit the site before the survey to identify potential obstacles such as buildings, trees or other structures.
2. Use aerial imagery: Use satellite imagery or aerial photographs to learn about the terrain and identify potential obstacles.
3. Communication with landowners: Speak with landowners or property managers to gather information about any potential obstacles on the site.
4. GPS and GIS technologies: Use GPS and GIS technologies to map out the survey area accurately. These tools help in planning the survey layout while considering existing obstacles.
5. Remote sensing tools: Use remote sensing tools, such as LiDAR or ground-penetrating radar, to detect underground obstacles or topographical features that might affect the survey.
6. Safety protocols: Put safety first by setting protocols for dealing with unexpected obstacles during fieldwork. This includes having appropriate safety equipment and contingency plans.

Evaluation

1. What is surveying?
2. Mention five common instruments used for surveying.
3. Mention five ways of avoiding obstacles in the field.
4. Identify two uses of the prismatic compass in surveying.

Classwork

As in the evaluation.

Assignment

1. List the procedures for plotting a traverse.
2. State two uses of the chain in surveying.

Conclusion: The teacher commends the students.