241) If the spacing of cross hairs in a stadia diaphragm of a tacheometer is 1.2 mm and the focal length of object glass is 24 cm, then the multiplying constant of tacheometer is
246) An imaginary line passing through the optical centre of the objective and the optical centre of the eye-piece in the telescope or a surveying instrument is called the
reciprocal levelling eliminates errors of non-parallel instrument and collimation axes
248) The difference between the sum of the angles of a plane triangle and the sum of the angles of a spherical triangle is one second when the triangle on the earth surface has an area of about
