Traverse Survey Plotting Methods Explained

Traverse survey plotting is the process of transferring the field measurements of a traverse (angles and distances) onto a drawing sheet to create a map or plan. There are several methods used for plotting a traverse, which generally fall into two categories: angle and distance methods, and coordinate methods.

Angle and Distance Plotting Methods

Angle and distance methods involve directly plotting the measured angles and distances on the drawing sheet. For each station after the first one, the plotting is done by measuring the angle from the previous line and then marking the distance along that angle. Common methods include:

• Protractor method: This is the simplest method. It involves using a protractor to plot the angles measured in the field and a scale to lay off the distances. While easy, it can be less accurate, especially for long traverses.
• Tangent method: This method uses the tangent of the angle to plot the direction. The angle is converted into a tangential offset at a convenient distance along the previous line. This method requires some calculation and is more accurate than the protractor method.
• Chord method: Similar to the tangent method, this method uses the chord length subtended by the angle to plot the direction. The angle is converted into a chord length at a fixed radius. This also requires calculation and offers better accuracy than the protractor method.

Coordinate Plotting Method

The Coordinate method is fundamentally different in its plotting technique, although it relies on angle and distance measurements from the field. In this method:

• Field angles and distances are used to calculate the coordinates (Northings and Eastings, or Latitudes and Departures) of each traverse station relative to a starting point.
• Plotting is then done by setting up a grid on the drawing sheet and plotting each station directly using its calculated X and Y coordinates.

While the Coordinate method uses angle and distance measurements to arrive at the coordinates, the plotting itself is done based on the coordinates on a grid, not by directly measuring the angle and distance from the previous point on the paper using tools like a protractor or by laying off tangents/chords.

Identifying the Method NOT Using Direct Angle and Distance Plotting

The question asks which option is NOT an angle and distance method traverse survey plotting. Based on the explanations:

• Chord of angle method is an angle and distance plotting method.
• Tangent of angle method is an angle and distance plotting method.
• Protractor method is an angle and distance plotting method.
• Coordinate method uses calculated coordinates for plotting, derived from angles and distances, but the plotting action itself is by coordinates on a grid, distinguishing it from the direct angle and distance plotting methods listed.

Therefore, the Coordinate method is the one that does not fit the description of a direct angle and distance traverse survey plotting method in the same way the others do.