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Which of the following methods is used when curve to be designed is short?
A) Linear method
B) Angular method
C) Tangent method
D) Curvature method
Linear method
Linear methods (or chain and tape methods) are used for setting out simple circular curves when the length of the curve is short and high precision is not required. These methods rely solely on linear measurements made with a chain or tape, without using angle-measuring instruments like a theodolite.
Linear methods (or chain and tape methods) are used for setting out simple circular curves when the length of the curve is short and high precision is not required. These methods rely solely on linear measurements made with a chain or tape, without using angle-measuring instruments like a theodolite.
O0тАЛ=RтИТR2тИТ(2LтАЛ)2тАЛ тАФ Mid-ordinate formula in linear setting out
OxтАЛ=R2тИТx2тАЛтИТ(RтИТO0тАЛ) тАФ Offset at distance x from the mid-point of the long chord
Linear methods use geometric properties of circles, chords, and tangents to locate points along the curve using chain or tape measurements. Offsets are measured either perpendicular or radial to a tangent or long chord to mark points along the curve.
Linear methods are suitable for short curves, sharp curves, and where low accuracy is acceptable.
Instruments required for linear methods are simple: chain, tape, arrows, and optical square.
Common linear methods include: Offsets from Long Chord, Successive Bisection of Chords, Offsets from Tangents, and Offsets from Produced Chords.
No angular measuring instruments (like theodolites) are needed.
Simple to execute in the field with basic surveying equipment.
Errors accumulate over longer distances, limiting use to short curves.
Low precision compared to angular setting out methods.
Setting out sharp circular curves in minor road intersections or street corners.
Short curves in canal alignments and minor railway tracks.
| Feature | Linear Method | Angular Method |
|---|---|---|
Equipment Used | Chain, Tape, Arrows, Optical Square | Theodolite, Total Station, Tape |
Suitability | Short curves, low precision work | Long curves, high precision work |
Cumulative Error | High (increases with curve length) | Low (independently measured angles) |
Angular methods (such as Rankine's method of deflection angles or Two-Theodolite method) are used when curves are long and require higher accuracy.
Option B (Angular method) is preferred for long curves with high precision.
Option C (Tangent method) is a subtype of linear/angular setting out, not a primary classification based on length.
Option D (Curvature method) is not a standard surveying classification for setting out curves.
A is correct тАФ Linear methods use simple chain and tape measurements, making them ideal for setting out short curves where high precision is not mandatory.
In competitive exams like GATE and SSC JE, remember: Linear methods = Short curves (Chain/Tape), Angular methods = Long/Precise curves (Rankine's Deflection Angle method using Theodolite).