152. In chain surveying tie lines are primarily provided
To check the accuracy of the survey
To take offsets for detail survey
To avoid long offsets from chain lines
To increase the number of chain lines
Correct answer: (C) To avoid long offsets from chain lines
153. In chain surveying, perpendiculars to the chain line are set out by
A theodolite
A prismatic compass
A level
An optical square
Correct answer: (D) An optical square
154. In direct method of contouring, the process of locating or identifying points lying on a contour is called
Ranging
Centring
Horizontal control
Vertical control
Correct answer: (D) Vertical control
155. In geodetic surveys higher accuracy is achieved, if
Curvature of the earth surface is ignored
Curvature of the earth surface is taken into account
Angles between the curved lines are treated as plane angles
None of these
Correct answer: (B) Curvature of the earth surface is taken into account
156. In horizontal angles, the error due to imperfect levelling of the plate bubble is
Large when sights are nearly level
Large for long sights
Less for steeply inclined sights
Large for steeply inclined sights
Correct answer: (D) Large for steeply inclined sights
157. In levelling operation
When the instrument is being shifted, the staff must not be moved
When the staff is being carried forward, the instrument must remain stationary
Both (a) and (b)
Neither (a) nor (b)
Correct answer: (C) Both (a) and (b)
158. In levelling operation,
The first sight on any change point is a back sight
The second sight on any change point is a fore sight
The line commences with a fore sight and closes with a back sight
The line commences with a back sight and closes with a foresight
Correct answer: (D) The line commences with a back sight and closes with a foresight
159. In optical reading instruments
The vertical circle is usually continuous from 0° to 359°
The readings increase when the telescope is elevated in the face left position
The readings decrease when the telescope is elevated in the face right position
All the above
Correct answer: (D) All the above
160. In precision theodolite traverse if included angles are read twice and the mean reading accepted using both verniers having a least count of 30". Assuming the instrument to be in perfect adjustment, linear measurements correct to 6 mm per 30 metre tape duly corrected for temperature, slope and sag, the angular error of closure not to exceed (where n is the number of traverse legs)