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In which type of surveying, we are considered earth surface as a spherical shape.
Geodetic surveying
Plane surveying
Both A and B
None of the above
Geodetic surveying
Geodetic surveying is a branch of surveying where the curvature of the earth's surface is taken into account. It is employed for large-area surveys (typically covering areas greater than 250 km2)to ensure high precision, as the discrepancy between the spherical and planar surface becomes significant at these scales.
Geodetic surveying is a branch of surveying where the curvature of the earth's surface is taken into account. It is employed for large-area surveys (typically covering areas greater than 250 km2)to ensure high precision, as the discrepancy between the spherical and planar surface becomes significant at these scales.
e=1−ab — represents the eccentricity of the terrestrial spheroid.
Δ=R2A⋅π180 — spherical excess correction for large triangles.
In geodetic surveying, the earth is modeled as an oblate spheroid or ellipsoid. Measurements are taken along curved lines (geodesics) rather than straight lines, and all plumb lines at different points are considered to converge at the center of the earth, necessitating the use of spherical trigonometry.
Geodetic surveying covers large geographical areas where Earth's curvature is non-negligible.
Plane surveying treats the earth's surface as a horizontal plane, valid for smaller extents.
The limit commonly cited for plane surveying is an area of 250 km2or a survey line length up to 18.2 km.
For geodetic surveys, the difference between the sum of angles in a spherical triangle and 180° is known as spherical excess.
Provides high degree of precision over large distances.
Essential for establishing national control networks and mapping vast territories.
Computationally complex requiring advanced spherical trigonometry.
Expensive and time-consuming compared to plane surveying.
Preparation of national and state maps.
Determination of the Earth's figure and gravity studies.
| Feature | Geodetic | Plane |
|---|---|---|
Earth Shape | Spherical/Ellipsoidal | Plane/Flat |
Area Limit |
| < 250 km2 |
In plane surveying, plumb lines are assumed to be parallel to each other.
Option B (Plane surveying) is incorrect because it ignores Earth's curvature, treating the surface as a flat plane.
For a survey line of 18.2 km, the difference in length between a straight line and a curved arc is only about 0.01 m, which is why plane surveying suffices for small areas.
A is correct — Geodetic surveying accounts for the curvature of the earth and is used for large-scale operations requiring high geodetic accuracy.
Always remember the 250 km2threshold; if the area is smaller, the earth is assumed flat to simplify calculations without sacrificing acceptable engineering tolerance.