Compass surveying uses bearing measurements (fore-bearing and back-bearing, related by the rule fore-bearing minus back-bearing equals 180°) taken with instruments such as the surveyors compass and prismatic compass to establish a traverse — a connected series of survey lines and stations used to map an area. Local attraction, a natural error source caused by external magnetic fields disturbing a station's magnetic needle, is detected when the fore-bearing/back-bearing difference at a line deviates from 180° and is corrected by identifying attraction-free stations and propagating angular corrections through the traverse; subsequent adjustments enforce the geometric closure condition that the internal angles of a closed traverse of N sides sum to (2N − 4) × 90°, within a permissible error tolerance of 15√N minutes. This belongs to the domain of surveying, specifically angular/directional measurement and traverse computation, as a parent discipline encompassing bearing systems (whole circle bearing, quadrantal bearing), meridians (true, magnetic, arbitrary), and closing-error adjustment methods such as the Bowditch (graphical/linear) method.
Compass surveying uses bearing measurements (fore-bearing and back-bearing, related by the rule fore-bearing minus back-bearing equals 180°) taken with instruments such as the surveyors compass and p…