Traversing

A traverse is a series of connected survey lines whose lengths and directions are measured, used to establish control points for mapping and construction. A closed traverse either returns to its starting point (loop traverse) or runs between two known points (link traverse); both allow the errors to be checked and distributed. An open traverse, ending at an unknown point, cannot be checked and should be avoided for control work.

Field work measures the angles at each station and the length of each line, today usually with a total station. The office work follows a fixed routine. First, check the angular misclosure against the theoretical sum and distribute it equally among the angles if within tolerance. Second, compute bearings of each line from the starting bearing and the adjusted angles. Third, compute latitudes (north components) and departures (east components) of each line. For a closed loop both sums should be zero; their actual values give the linear misclosure. Fourth, adjust by the Bowditch (compass) rule, which distributes corrections in proportion to line length, or the transit rule, which uses the sizes of the latitudes and departures.

Finally, coordinates of each station are found by adding the adjusted components. For large or precise networks, least squares adjustment replaces these rules and gives realistic accuracy estimates. Traverses are now often combined with GNSS control, which fixes a few points absolutely while the traverse provides dense local control.