Method of taking triangulation observation

(1) The minimum requirement for tertiary and minor triangulation shall be two arcs observed on different zeros: Provided that two swings observed on different faces and different zeros may be sufficient for observations to points situated less than 2,000 metres distance. (2) An arc of angular observations for triangulation shall consist of two swings observed in opposite directions on the same zero, one swing being on face left and the other on face right. (3) For each arc a suitable reference station shall be selected and both swings of the arc shall be closed on to it, and the misclosure of each swing shall be appropriate to the class of theodolite used. (4) The difference between measurements of any angle on different arcs shall be appropriate to the class of theodolite used. (5) Where electronic distance measuring equipment is used sufficient observations shall be taken to eliminate any ambiguities and achieve the accuracy required by regulation 8.