TGPSC HMWSSB Manager Surveying & GIS previous year questions with answers
Every Surveying & GIS question asked in the TGPSC HMWSSB Manager (Engineering) papers on this site, grouped by topic. Answers come from TSPSC's final key; each has a short explanation.
Practise Surveying & GIS onlineSurveying
If θ be the angle of slope and the length of chain is 30m, then the correction to be applied per chain length is
- 30 (1 - sec θ) m
- 30 (1 - cos θ) m
- 30 (sec θ - 1) m
- 30 (cos θ - 1) m
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Answer: (3) 30 (sec θ - 1) m
When chaining down a slope, a 30 m chain laid along the ground covers only 30 cos θ horizontally, so the arrow is set forward by the hypotenusal allowance 30(sec θ − 1) m in each chain length to make the horizontal distance a full 30 m. Option (2), 30(1 − cos θ), is instead the slope correction subtracted from a length already measured along the slope.
Which one of the following angles can be set out with the help of French cross staff?
- 180°
- 90°
- 45°
- any angle
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Answer: (3) 45°
A French cross staff is an octagonal tube with sighting slits on all eight faces, so unlike the ordinary open cross staff (which gives only right angles) it can also set out 45° angles. It cannot set out any arbitrary angle; that needs an adjustable cross staff.
The line Joining points of equal dip is called
- Isoclinic lines
- Aclinic lines
- Isogonic lines
- Agonic lines
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Answer: (1) Isoclinic lines
Isoclinic lines join places of equal magnetic dip, and the aclinic line joins places of zero dip. Isogonic and agonic lines refer to declination (equal and zero declination respectively), not dip.
If the forebearing of a line AB is 50° and that of line BC is 20°, then the included angle between the lines is
- 70°
- 120°
- 220°
- 150°
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Answer: (4) 150°
Back bearing of AB = 50° + 180° = 230°, so the included angle at B = FB of BC − BB of AB = 20° − 230° + 360° = 150°. Equivalently, the line deflects 50° − 20° = 30° to the left at B, and 180° − 30° = 150°.
When contours of different elevations cross each other, it indicates
- Level surface
- Overhanging cliff
- Saddle
- Vertical cliff
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Answer: (2) Overhanging cliff
Contours of different elevations can intersect only where the ground overhangs, as in an overhanging cliff or cave. For a vertical cliff the contours merge into one line without crossing, and a saddle shows as two sets of closed contours between two summits.
In theodolite survey, the telescope is said to be inverted, if the
- Vertical circle is to the right of the observer and the bubble of the telescope is up
- Vertical circle is to the right of the observer and the bubble of the telescope is down
- Vertical circle is to the left of the observer and the bubble of the telescope is up
- Vertical circle is to the left of the observer and the bubble of the telescope is down
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Answer: (2) Vertical circle is to the right of the observer and the bubble of the telescope is down
In the normal (face left) position the vertical circle is on the observer's left and the telescope bubble is up. After transiting, the telescope is inverted (face right): the vertical circle comes to the observer's right and the bubble is down.
If the RL of a BM is 100m, the back sight is 1.415m and the foresight is 1.670m, the RL of the forward station is
- 101.670m
- 101.415m
- 99.745m
- 98.585m
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Answer: (3) 99.745m
Height of instrument = RL of BM + BS = 100 + 1.415 = 101.415 m. RL of forward station = HI − FS = 101.415 − 1.670 = 99.745 m.
In Simpson's formula for areas calculation, the line joining the top of the ordinates is considered as
- elliptical
- circular
- parabolic
- straight
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Answer: (3) parabolic
Simpson's one-third rule assumes that the boundary between every three consecutive ordinates is an arc of a parabola. The trapezoidal rule instead assumes straight lines between the tops of adjacent ordinates.
To obtain the correct volume using the trapezoidal rule, the prismoidal correction should always be
- Multiplied
- Added
- Subtracted
- Zero
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Answer: (3) Subtracted
The trapezoidal (average end area) rule usually overestimates the volume of earthwork compared with the prismoidal formula. The prismoidal correction is therefore subtracted from the trapezoidal volume to get the correct volume.
Remote Sensing & GIS
In Geographic information system, line in polygon method is characteristic of
- Buffer operation
- Raster overlay
- Intersecting operation
- Vector overlay
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Answer: (4) Vector overlay
Point-in-polygon, line-in-polygon and polygon-on-polygon are the three types of vector overlay, where geometric features are intersected with polygon layers. Raster overlay instead combines layers cell by cell.