Difference Between Geodetic Surveying and Plane Surveying (With Numerical Values)
Definition (1 mark)
- Plane Surveying: A type of surveying in which the earth’s surface is assumed to be flat (plane surface) and curvature is ignored.
- Geodetic Surveying: A type of surveying in which the curvature of the earth is considered and high precision measurements are taken over large areas.
Differences Between Plane and Geodetic Surveying (4–5 marks)
| Basis | Plane Surveying | Geodetic Surveying |
|---|---|---|
| Earth assumption | Earth is assumed flat | Earth is considered spherical/ellipsoidal |
| Area covered | Small areas (generally < 250 km²) | Large areas (generally > 250 km²) |
| Accuracy | Moderate accuracy | Very high accuracy |
| Curvature of earth | Ignored | Considered in calculations |
| Lines | Straight lines are assumed | Curved lines (geodesics) are used |
| Level lines | Parallel lines assumed | Converging lines considered |
| Use of instruments | Simple instruments like chain, tape, compass | Precise instruments like theodolite, EDM, GPS |
| Error handling | Errors are small and often ignored | Errors are carefully computed and adjusted |
| Cost & time | Less expensive and faster | More expensive and time-consuming |
| Purpose | Local projects, building, roads | National mapping, large engineering projects |
Numerical/Scale Concept (Important Point)
- In plane surveying, curvature effect is negligible when area is less than about 250 km² (radius of curvature error is very small).
- In geodetic surveying, used for areas greater than 250 km², where earth curvature introduces significant error if ignored.
Conclusion (1 mark)
Plane surveying is suitable for small-scale, low-precision work, while geodetic surveying is used for large-scale, high-precision mapping where earth curvature must be considered.
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