Understanding Traverse Adjustment Methods

Traverse adjustment is a crucial step in surveying to eliminate the errors that accumulate during field measurements. These errors include both angular errors (in measured angles) and linear errors (in measured lengths and bearings/azimuths). The goal of adjustment is to make the traverse geometrically consistent, especially for closed traverses where the end point should coincide with the starting point or a point of known position.

Methods for Traverse Adjustment

There are several methods used for adjusting a traverse. Different methods handle the distribution of angular and linear errors in different ways. Let's look at the options provided:

• Transit method: This method is specifically designed for adjusting the angular error in a traverse. The total angular error (the difference between the measured sum of internal angles and the theoretically correct sum) is calculated and distributed among the measured angles. This adjustment is typically done before adjusting the linear measurements. The angular error distribution in the transit method is often done equally among all angles or weighted based on the precision of the measurements.
• Graphical method: This method involves plotting the traverse to scale and visually adjusting the lines to close the traverse. It is less precise than numerical methods and is not primarily focused on rigorous angular adjustment but rather an overall graphical correction.
• Bowditch's method (Compass Rule): This is a widely used method that adjusts both angular and linear errors. The angular error is first distributed (often equally among angles or prorated), and then the linear errors (in latitudes and departures) are distributed proportionally to the length of each traverse leg. While it adjusts angular errors, its rule for distributing linear errors is based on length.
• Axis method: This is not a standard, recognized method for traverse adjustment in surveying.

Focusing on Angular Measurement Adjustment

The question specifically asks for a method employed for angular measurements. Among the standard methods, the Transit method puts a direct emphasis on adjusting the observed angles based on the total angular closing error. While Bowditch's method also addresses angular error, the Transit method is more explicitly associated with the initial step of balancing the angles before proceeding to linear adjustments (which might then use a rule like the Transit rule for linear errors, also different from Bowditch's linear rule).

Therefore, the method primarily employed for adjusting angular measurements in a traverse is the Transit method.