In an electrical tachymeter for determining the coordinates of fixed points by means of an electrical theodolite and range finder and infinitely fine drives for moving the theodolite in a horizontal circle and a vertical circle, the theodolite is provided, for mechanically controlling its movements, with stepping motors which are coupled to the horizontal fine drive and vertical fine drive and the rotary movement of which is controlled by pulses supplied by a microprocessor. This device can be usefully used where observations are required over a prolonged period in order to check the occurrence of ground movements.
