## Methods of Contouring
Definition (1 mark)
Contouring is the process of determining the elevation of points on the ground and representing them by contour lines on a map.
Methods of Contouring (2.5–3 marks)
There are two main methods:
1. Direct Method
- Contours are traced directly on the ground.
- Points of equal elevation are located using a levelling instrument.
- These points are then plotted to form contour lines.
👉 Features:
- Highly accurate
- Time-consuming and costly
👉 Example: Used for small areas where high precision is required.
2. Indirect Method
- Elevations of selected points are measured.
- Contours are drawn by interpolation between these points.
👉 Common techniques:
- Method of squares (grid method)
- Cross-section method
- Radial line method
👉 Features:
- Faster and economical
- Less accurate than direct method
👉 Example: Used in large area surveys like road or railway projects.
Key Concept
- Direct method → accurate but slow
- Indirect method → faster but involves estimation (interpolation)
Conclusion (1 mark)
Contouring can be done by direct or indirect methods, where the choice depends on accuracy required, area size, and available time, with indirect methods being more commonly used in practice.
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