Traverse

Definition

A traverse is a fundamental surveying technique that establishes a series of connected survey lines forming a path across terrain. Each line segment connects two survey points, with measured distances and angles between consecutive lines. Traverses form the backbone of many surveying projects, providing a framework for mapping land features, establishing property boundaries, and conducting engineering surveys.

Types of Traverses

Open Traverse

An open traverse begins at one point and terminates at a different point, without returning to the starting position. This type is commonly used for:

Route surveying (roads, railways, pipelines)

Linear infrastructure projects

Reconnaissance surveys

Open traverses provide less error checking capability than closed traverses, making them suitable for preliminary investigations.

Closed Traverse

A closed traverse begins and ends at the same point, forming a polygon. This configuration offers superior error detection and correction capabilities. Closed traverses are preferred for:

Property boundary surveys

Site surveys

Construction layout

The geometric closure of a closed traverse allows surveyors to calculate and verify measurement accuracy through mathematical closure checks.

Measurement Procedures

Horizontal Angles

Horizontal angles are measured between consecutive survey lines using theodolites or total stations. The angle measurements provide directional control and allow calculation of bearings or azimuths for each traverse segment.

Distances

Distances between traverse points are measured using:

Steel measuring tapes (for short distances)

Electronic distance measurement (EDM) devices

Total stations (combined angle and distance measurement)

Accurate distance measurement is critical for establishing precise coordinates.

Coordinate Calculation

Traverse coordinates are calculated using measured distances and angles. The bearing or azimuth of each line is determined, then latitude and departure (northing and easting components) are calculated for each segment. These components accumulate to establish the coordinates of each traverse point relative to a known reference system.

Error Analysis and Adjustment

Closure Error

In closed traverses, mathematical closure checks identify measurement errors. The sum of interior angles should equal (n-2) × 180°, where n is the number of vertices. Linear closure error occurs when the calculated endpoint fails to match the actual starting point.

Adjustment Methods

Common adjustment techniques include:

Bowditch method: Distributes errors proportionally to traverse length

Least squares adjustment: Uses statistical methods for optimal error distribution

Transit rule: Adjusts coordinates based on angle and distance errors

Accuracy Standards

Traverse accuracy depends on:

Instrument precision

Measurement methodology

Environmental conditions

Adjustment procedures

Typical relative accuracy ranges from 1:1000 for reconnaissance traverses to 1:10000 or better for precise engineering surveys.

Modern Applications

Contemporary traverse surveying employs:

Total stations: Simultaneous angle and distance measurement

GPS/GNSS: For establishing control networks

3D traversing: Measuring vertical angles for three-dimensional data

Automated data collection: Digital recording and processing

Advantages and Limitations

Advantages

Relatively simple field procedures

Flexible survey design

Cost-effective for many applications

Suitable for diverse terrain

Limitations

Requires multiple instrument setups

Time-consuming for large areas

Error accumulation in long traverses

Limited by line-of-sight requirements

Conclusion

Traverse surveying remains an essential technique in modern surveying practice, combining classical methodology with contemporary technology. Whether conducting property surveys, engineering projects, or mapping infrastructure, traverses provide reliable frameworks for establishing ground control and mapping spatial data accurately.