What is the difference between an open traverse and a closed traverse?

Short Answer:

The difference between an open traverse and a closed traverse is based on how the traverse lines connect. An open traverse starts at a known point and ends at an unknown point, so it doesn’t form a complete loop. It is usually used in road, pipeline, or canal surveys where a continuous path is followed.

A closed traverse, on the other hand, starts and ends at the same point or two known points. It forms a complete loop and allows checking and correcting of errors. Closed traverses are commonly used in boundary and land surveys where accuracy and error detection are important.

Detailed Explanation:

Difference between an open traverse and a closed traverse

Traverse surveying is a method where a series of connected lines are measured for both distance and angles to determine positions and layout. These lines form a pattern known as a traverse. Based on how these lines are connected, traverses are classified into two types: open traverse and closed traverse. Both have different purposes, accuracy levels, and applications.

Open Traverse

An open traverse begins at a known point but ends at an unknown point. It does not return to the starting point or connect to another known location. Because of this, there is no way to check for closing errors directly.

  • Used mainly for projects like highways, railways, canals, and pipe routes, where the survey moves in a straight or curved path over a long distance.
  • Since there’s no loop or closure, surveyors must be extra careful to minimize and record errors.
  • Angular and linear measurements are taken at every station, but error correction methods are limited.

Closed Traverse

A closed traverse begins and ends at the same known point or two different known points. It forms a loop or closed figure such as a triangle, square, or polygon. This allows surveyors to check and balance both angle and distance errors.

  • Commonly used in property boundary surveys, construction layouts, and topographic mapping.
  • Offers better accuracy because total internal angles can be checked using geometric formulas.
  • Errors in measurements can be identified and adjusted using techniques like Bowditch’s rule or Transit rule.
  • The final drawing or layout from a closed traverse is considered more reliable due to this checking ability.

Key Differences:

  • Connection: Open traverse does not return to the starting point; closed traverse does.
  • Error checking: Open traverse has no natural way to check errors; closed traverse allows error checking.
  • Usage: Open traverse is used for linear projects; closed traverse is used for enclosed areas.
  • Accuracy: Closed traverse provides higher accuracy due to its ability to adjust errors.
  • Examples: Open traverse for roads and pipelines; closed traverse for land and property boundaries.

Surveyors choose between these two types depending on the project requirement, nature of the land, and the need for accuracy. In legal and engineering works, closed traverse is often preferred due to its self-checking nature.

Conclusion

An open traverse is a survey that does not form a loop and ends at an unknown point, while a closed traverse forms a complete loop or ends at a known point, allowing error checking. Closed traverses are more accurate and are used in boundary and area surveys, while open traverses are suitable for route-based projects like roads and canals.