While viewing through a level telescope and moving the eye slightly, a relative movement occurs between the image of the levelling staff and the cross hairs. The instrument is

Related MCQs

• When a staff is sighted through the telescope, a certain length of staff is intercepted by the stadia lines. The staff intercept varies with the distance at which the staff is held.
• If altitude bubble is provided both on index frame as well as on telescope of a theodolite, then the instrument is levelled with reference to i) altitude bubble on index frame ii) altitude bubble on index frame if it is to be used as a level iii) altitude bubble on telescope iv) altitude bubble on telescope if it is to be used as a level The correct answer is
• It is required to find the difference in elevation between two points A and B. During levelling, it is found that the staff reading at B is more than the staff reading at A. It indicates that the point A is
• The cross hairs in the surveying telescope are placed
• When the effect of refraction is taken into account in levelling, the true staff reading is obtained by subtracting the correction for refraction from the observed staff reading.
• The magnification of a telescope is the ratio of the angle subtended at the eye by the virtual image of the object to that subtended by the object.
• In levelling, the correction for curvature (in metres) is equal, where D = Distance from the level to the staff reading in kilometres.
• When the image formed by the objective is not situated in the plane of cross-hairs,
• The image formed by the objective in the plane of cross hairs is
• Generally, the deflection angle is measured twice, once with the telescope normal and once with the telescope reversed.