GATE — Agricultural Engineering (AG) · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersMeasuring land, levels and volumes, from chain survey to total station and GNSS, and designing land grading.
In the exams: GATE AG Section 4 (surveying asked in 7 of 8 papers 2019–26); ICAR AIEEA-PG Unit VII; TNPSC Unit I; RPSC AAE Unit 1; NCEES PE surveying
GATE — Agricultural Engineering (AG), Section 4 Soil and Water Conservation Engineering
Short numericals, often NAT: tape corrections (temperature, pull, sag, slope, wrong length and area), RLs by HI and rise-and-fall with the arithmetic check, reciprocal levelling, curvature and refraction, WCB to QB and included angles, traverse closing error and Bowditch corrections, stadia distance, trapezoidal and Simpson areas, prismoidal and trapezoidal volumes. Since 2021 the syllabus also names total station and GPS.
How our questions for GATE spread across the units of Surveying & Levelling. Difficulty: 33 easy, 38 medium, 18 hard.
| Theodolite traversing and closing error | 11 | |
| Chain and tape surveying, including tape corrections | 10 | |
| Levelling: rise-and-fall and height-of-instrument methods | 8 | |
| Reciprocal levelling | 8 | |
| Compass traversing and bearings | 7 | |
| Plane table surveying | 7 | |
| Contouring | 7 | |
| Earthwork volume computation | 7 | |
| Total station | 6 | |
| GPS/GNSS surveying | 6 | |
| Computation of area: trapezoidal and Simpson's rules | 6 | |
| Land grading and levelling design | 6 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
In chain surveying, a well-conditioned triangle is one in which
C. angles are 30°–120°
The apex of a triangle is fixed by intersecting arcs; if an angle is very acute or very obtuse, the arcs meet at a flat angle and a small taping error moves the plotted point a long way. The usual rule is to keep angles between about 30° and 120°. An equilateral triangle is ideal but not required, and a right angle has no special merit.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
In a prismatic compass, the zero of the graduated ring is placed at the south end because
A. sighting is through a prism opposite the object, so a north sight must read 0° at that end
The ring is fixed to the needle and read through the prism at the eye end, diametrically opposite the object vane; to read 0° on a northward sight the zero must sit at the south end, and the figures are written inverted to read correctly through the prism. It reads whole-circle, not quadrantal, bearings, and its ring does not rotate with the sight (that is the surveyor's compass).
Further reading: Punmia, Jain and Jain, Surveying Vol. I
A vernier theodolite has main-scale divisions of 20 minutes and 60 vernier divisions. What is its least count?
C. 20 seconds
Least count = value of one main-scale division / number of vernier divisions = 20′/60 = 1/3′ = 20″.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
Taking the mean of face-left and face-right observations of a horizontal angle eliminates all of the following EXCEPT
D. error due to the vertical axis not being truly vertical
Face changes reverse the sign of collimation, trunnion-axis and index errors, so they cancel in the mean. A tilted vertical axis tilts the horizontal axis the same way on both faces, so it does not cancel; careful levelling is the only remedy.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
The transit rule for balancing a traverse is preferred over Bowditch's rule when
D. angles are measured more precisely than distances
The transit rule distributes corrections in proportion to the size of each latitude and departure, which assumes angles are good and lengths poorer (theodolite with tape). Bowditch assumes equal effect of angular and linear errors and is the usual rule for compass traverses. Neither can be applied to an open traverse.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
An RTK GNSS survey gives an ellipsoidal height of 18.6 m at a point where the geoid undulation N from the geoid model is −52.3 m. What is the orthometric height (height above the geoid)?
C. 70.9 m
H = h − N = 18.6 − (−52.3) = 70.9 m. Where the geoid lies below the ellipsoid (negative N), orthometric heights exceed ellipsoidal heights. Adding N gives -33.7 m; using the ellipsoidal height as if it were above mean sea level is the classic mistake.
Further reading: Ghilani and Wolf, Elementary Surveying
Simpson's one-third rule can be applied directly only when the number of
A. ordinates is odd (an even number of intervals)
The rule fits a parabola over each pair of strips, so the number of strips must be even and the number of ordinates odd. With an even number of ordinates, the last strip is computed separately by the trapezoidal rule.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
An area measured on a 1:2000 plan is 42.5 cm². What is the ground area?
C. 1.70 ha
1 cm² on the plan = (20 m)² = 400 m². So 42.5 × 400 = 17,000 m² = 1.70 ha. Scaling by the RF once instead of squared is the classic slip. 17.0 ha is a factor-of-ten slip; 0.085 ha scales by 20 m once (42.5 × 20 = 850 m²) instead of squared.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
A 40 m long prismoid has end areas 12.0 and 24.0 m² and a mid-section area (computed from the mid-depth) of 17.5 m². What is its volume?
B. 706.7 m³
V = (L/6)(A1 + 4Am + A2) = (40/6)(12 + 70 + 24) = 706.7 m³. Average end area gives 720.0 m³ (an overestimate for a prismoid); using L/3 doubles the answer because L here is the full length. 1413.3 m³ uses L/3; 700.0 m³ multiplies the mid-section area by the length.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
When is the plane method of land-grading design NOT the best choice?
A. On fields so irregular that a single plane would require excessive earth movement
A single best-fit plane is efficient for fairly uniform fields; where the surface is strongly irregular, profile, plan-inspection or contour-adjustment methods allow varying grades and cut far less earth.
Further reading: Schwab et al., Soil and Water Conservation Engineering
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