Tamil Nadu PSC — Agricultural Engineering (Code 164, degree standard) · India · Tamil Nadu Public Service Commission
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
Tamil Nadu PSC Code 164 (Unit I) and Rajasthan PSC Assistant Agriculture Engineer (Unit 1)
Degree-standard recall and computation: chain survey and obstacles, compass and local attraction, plane-table resection, levelling book reduction, contouring for bunds and terraces, land development and levelling design, and total station.
How our questions for Tamil Nadu PSC spread across the units of Surveying & Levelling. Difficulty: 42 easy, 39 medium, 5 hard.
| Chain and tape surveying, including tape corrections | 10 | |
| Compass traversing and bearings | 9 | |
| Theodolite traversing and closing error | 9 | |
| Plane table surveying | 8 | |
| Levelling: rise-and-fall and height-of-instrument methods | 8 | |
| Contouring | 8 | |
| Earthwork volume computation | 7 | |
| Reciprocal levelling | 6 | |
| Computation of area: trapezoidal and Simpson's rules | 6 | |
| Total station | 5 | |
| GPS/GNSS surveying | 5 | |
| Land grading and levelling design | 5 |
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
Which method of orienting a plane table is the more accurate?
A. Back-sighting along a previously drawn line
Back-sighting relies on a line already plotted, so it is as accurate as the plotting. The trough compass is quick but subject to local attraction and needle errors, so it is used only where no back station is available.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
A point on which both a foresight and a backsight are taken in a levelling line is called a
C. change point
At a change (turning) point the foresight closes one set-up and the backsight opens the next, carrying the RL forward. A benchmark has a known RL; an intermediate station has only one reading.
Further reading: Punmia, Jain and Jain, Surveying Vol. I
Which indirect method of contouring is most suitable for a long narrow strip such as a canal alignment?
B. Cross-sections at intervals along the centre line
For a route the ground is profiled along the centre line and cross-sectioned at regular chainages, which directly gives the data for earthwork. Grids suit compact areas; radial tacheometry suits hilly country.
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
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
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