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Which type of surveying is preferred, when area is more than 250 km² ?
Geodetic surveying
Plane surveying
Both A and B
None of the above
Geodetic surveying
Geodetic surveying is preferred when the area exceeds 250 km2 because it accounts for the Earth's curvature, unlike plane surveying which assumes a flat surface. For larger areas, the curvature error becomes significant and can no longer be ignored.
Geodetic surveying is preferred when the area exceeds 250 km2 because it accounts for the Earth's curvature, unlike plane surveying which assumes a flat surface. For larger areas, the curvature error becomes significant and can no longer be ignored.
e=12R2l3 — where e is the error due to curvature, l is the length of the line, and R is the radius of the Earth.
In geodetic surveying, the survey lines are considered as arcs of the Earth's surface rather than straight lines. This method uses spherical trigonometry to calculate coordinates and distances, ensuring high precision for large-scale engineering projects and mapping.
Plane surveying assumes the earth is a flat plane.
Geodetic surveying considers the ellipsoidal shape of the earth.
The limit of 250 km2 is based on the maximum allowable error for small-scale survey work.
Triangulation and trilateration are primary methods in geodetic surveying.
High accuracy over extensive geographical areas.
Essential for national boundary demarcation and global mapping.
Requires complex spherical trigonometric calculations.
Involves high cost and specialized instrumentation.
Large-scale national projects.
Topographical mapping of countries.
Determination of the Earth's magnetic field and shape.
| Feature | Geodetic | Plane |
|---|---|---|
Earth Surface Assumption | Considered Curved | Considered Flat |
Area Limit |
| < 250 km2 |
Plane surveying is sufficient for small areas because the difference between an arc and a chord is negligible.
For a distance of 18.2 km, the difference between arc and chord is only about 0.1 m.
A is correct — Geodetic surveying is necessary for areas larger than 250 km2 to account for the curvature of the Earth.
Remember that 250 km2 is the threshold; if the question asks for the survey type for small local projects, always choose Plane Surveying.