Traverse (surveying)

Traverse is a method in the field of surveying to establish control networks. It is also used in geodetic work. Traverse networks involved placing the survey stations along a line or path of travel, and then using the previously surveyed points as a base for observing the next point. Traverse networks have many advantages of other systems, including:


 * Less reconnaissance and organization needed;
 * While in other systems, which may require the survey to be performed along a rigid polygon shape, the traverse can change to any shape and thus can accommodate a great deal of different terrains;
 * Only a few observations need to be taken at each station, whereas in other survey networks a great deal of angular and linear observations need to be made and considered;
 * Traverse networks are free of the strength of figure considerations that happen in triangular systems;
 * Scale error does not add up as the traverse as performed. Azimuth swing errors can also be reduced by increasing the distance between stations.

The traverse is more accurate than triangulateration (a combined function of the triangulation and trilateration practice).

Types
Frequently in surveying engineering and geodetic science, control points (CP) are setting/observing distance and direction (bearings, angles, azimuths, and elevation). The CP throughout the control network may consist of monuments, benchmarks, vertical control, etc.

Open/Free
An open, or free traverse (link traverse) consist of known points plotted in any corresponding linear direction, but do not return to the starting point or close upon a point of equal or greater order accuracy. It allows geodetic triangulation for sub-closure of three known points; known as the "Bowditch rule" or "compass rule" in geodetic science and surveying, which is the principle that the linear error is proportional to the length of the side in relation to the perimeter of the traverse.
 * Open survey is utilised in plotting a strip of land which can then be used to plan a route in road construction. The terminal (ending) point is always listed as unknown from the observation point.

Closed
A closed traverse (polygonal, or loop traverse) is a practice of traversing when the terminal point closes at the starting point. The control points may envelop, or are set within the boundaries, of the control network. It allows geodetic triangulation for sub-closure of all known observed points.
 * Closed travese is useful in marking the boundaries of wood or lakes. Construction and civil engineers utlize this practise for preliminary surveys of proposed projects in a particular designated area.  The terminal (ending) point closes at the starting point.

Usages

 * Control point — the primary/base control used for preliminary measurements; it may consist of any known point capable of establishing accurate control of distance and direction (i.e. coordinates, elevation, bearings, etc).
 * 1) Starting – It is the initial starting control point of the traverse.
 * 2) Observation – All known control points that are setted or observed within the traverse.
 * 3) Terminal – It is the initial ending control point of the traverse; its coordinates are unknown.