GATE 2017 CE (CE1) – Question 45

Geomatics Engineering · Distance and angle measurement, levelling, traversing, triangulation, total station · 2 marks · MTA

Observed fore/back bearings are PQ 46°15′ / QP 226°15′; QR 108°15′ / RQ 286°15′; RS 201°30′ / SR 20°30′; ST 321°45′ / TS 141°45′. Which station(s) are most likely affected by local attraction?

Only R
Only S
R and S
P and Q

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Correct answer: MTA

Explanation

For an unaffected line, fore and back bearings differ by exactly 180°. PQ and ST satisfy this, suggesting P, Q, S and T are unaffected. QR differs by 178°, implicating R; RS differs by 181°, also implicating R while S is supported by ST. Thus the most likely affected station is R alone, A. The discrepancies at R are not mutually consistent, so they do not yield one exact correction. The revised official key awards marks to all for this question; that grading takes precedence over the likely intended A.

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