Indian Forest Service Examination (IFoS) — Forestry optional · India · Union Public Service Commission
Original practice questions written to the published syllabus · not past papersMeasuring and mapping forest land: chain, compass and plane-table survey, levelling and contouring, area computation, GNSS and the reading of topographic maps. General surveying is covered in the Agricultural Engineering track (surveying-levelling); this subject applies it to forest boundaries and compartments.
In the exams: IFoS Forestry Paper II Section A (surveying and forest engineering); PRC Forest Engineering and Utilization (survey); state Range Forest Officer exams
How our questions for Indian Forest Service Examination spread across the units of Forest Surveying & Mapping. Difficulty: 2 easy, 26 medium, 16 hard.
| Compass survey: bearings, declination, closing error | 6 | |
| Levelling and contouring | 6 | |
| National mapping agencies and systems | 6 | |
| Chain and tape survey | 5 | |
| Plane-table survey | 5 | |
| Computation of areas and volumes | 5 | |
| Topographic maps and map reading | 5 | |
| Demarcation of forest boundaries and compartments | 5 | |
| GNSS in forest survey and its accuracy under canopy | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A steel tape standardised at 20 °C measures 100 m at 35 °C. With α = 11.6 × 10⁻⁶ per °C, what is the temperature correction?
A. +17.4 mm
α(T − T₀)L = 11.6 × 10⁻⁶ × 15 × 100 m = 0.0174 m = 17.4 mm, added because the tape has expanded and reads short.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
In chain triangulation, a well-conditioned triangle has no angle smaller than about:
D. 30°
Angles between about 30° and 120° keep small length errors from distorting shape.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
A closed compass traverse of perimeter 1000 m has ΣL = +1.2 m and ΣD = −1.6 m. What are the closing error and relative precision?
C. 2.0 m; 1 in 500
√(1.2² + 1.6²) = 2.0 m; 2/1000 = 1 in 500. 2.8 adds the components directly.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
Fore and back bearings of a line differ by 172° instead of 180°. The most likely cause is:
D. Local attraction
Local attraction from iron or magnetic rock deflects the needle at one station; declination affects both bearings equally.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
Locating the position of the plane-table station itself from sightings to three plotted points is the:
D. Three-point resection problem
Resection with three visible points; Lehmann's rules guide the trial-and-error solution.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
At small mapping scales, which plane-table setup error matters least?
D. Centring
A small centring displacement is invisible at small scale, whereas orientation errors rotate every ray.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
For the same offsets (0, 4, 6, 5, 0 m at 10 m), what area does Simpson's rule give?
B. 160 m²
(10/3) × [(0 + 0) + 4(4 + 5) + 2(6)] = (10/3) × 48 = 160 m².
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
Why does a graphic scale bar remain useful when a map is photocopied at a different size?
A. It changes size with the map
A representative fraction becomes wrong when the map is enlarged or reduced; the bar scales with it.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
A boundary register records for each pillar its number, coordinates, bearing and distance to the next pillar, and condition. Its main purpose is to:
B. To relocate pillars and prove encroachment
Accurate records allow pillars to be re-established and support enforcement.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
Which datum is used by GPS?
B. WGS 84
WGS 84 is a global Earth-centred datum; the others are older local datums.
Further reading: See the manual sources: Punmia et al.; Bannister et al.; Ghilani and Wolf; Iliffe and Lott; NSSDA 1998
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