Traverse (surveying)

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Traverse is a method in the field of surveying to establish control networks.[1] It is also used in geodesy. Traverse networks involve placing 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, 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 is performed. Azimuth swing errors can also be reduced by increasing the distance between stations.

The traverse is more accurate than triangulateration[2] (a combined function of the triangulation and trilateration practice).[3]

Types[edit]

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.

Diagram of an open traverse
Diagram of a closed traverse

Open/Free[edit]

An open, or free traverse (link traverse), consists of a series of linked traverse lines which do not return to the starting point to form a polygon.[4]

  • Open survey is utilised in plotting a strip of land which can then be used to plan a route in road construction.[5]

Closed[edit]

A closed traverse (polygonal, or loop traverse) is a series of linked traverse lines where the terminal point closes at the starting point.[6] A closed traverse enables a check by plotting or computation, with any gap called the linear misclosure. When within acceptable tolerances, the misclosure can be distributed by adjusting the bearings and distances of the traverse lines using a systematic mathematical method so the adjusted measurements close. The "Bowditch rule" or "compass rule" in geodetic science and surveying assumes that linear error is proportional to the length of sides in relation to the perimeter of the traverse. Allowable misclosure is decided upon a case by case basis.

  • Closed traverse is useful in marking the boundaries of wood or lakes.[7] Construction and civil engineers utilize this practice for preliminary surveys of proposed projects in a particular designated area. The terminal (ending) point closes at the starting point.

Compound[edit]

A compound traverse is where an open traverse is linked at its ends to an existing traverse to form a closed traverse. The closing line may be defined by coordinates at the end points which have been determined by previous survey. The difficulty is, where there is linear misclosure, it is not known whether the error is in the new survey or the previous survey.

Notes[edit]

Usages[edit]

  • 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 – The initial starting control point of the traverse.
  2. Observation – All known control points that are setted or observed within the traverse.
  3. Terminal – The initial ending control point of the traverse; its coordinates are unknown.

References[edit]

  1. ^ B. C. Punmia, Ashok Kumar Jain (2005). Surveying. Firewall Media. ISBN 81-7008-853-4. 
  2. ^ Chrzanowski and Konecny, (1965); Adler and Schmutter (1971).
  3. ^ Schofield, Wilfred (2001). Engineering Surveying.Butterworth-Heinemann. ISBN 978-0-7506-4987-2.
  4. ^ Ghilani, Charles D.; Wolf, Paul R. (2008). Elementary surveying: an introduction to geomatics. Prentice Hall. p. 226. ISBN 978-0-13-615431-0.
  5. ^ O'Flaherty, Coleman A. (2002). Highways: the location, design, construction and maintenance of road pavements. Butterworth-Heinemann. p. 17. ISBN 978-0-7506-5090-8.
  6. ^ Siegle, Arthur (1979). Basic plane surveying. Delmar. p. 82. ISBN 978-0-8273-1698-0.
  7. ^ Duggal, S. K. (2004). Surveying, Volume 1. Tata McGraw-Hill. p. 177. ISBN 978-0-07-053470-4.