traverse computations
chapter fourteen
Direction Calculation Rules
Direction calculations can be performed in either a clockwise or counter-clockwise manner about a traverse. There are specific rules for calculating in either direction.
To calculate azimuths clockwise around a traverse: Subtract the adjusted interior angle from the back azimuth of the preceding line.
To calculate azimuths counter-clockwise around a traverse: Add the adjusted interior angle to the back azimuth of the preceding line.
Procedure For Calculating Directions
The following is the step-by-step procedure for calculating azimuths clockwise. See the Table on the following page for the solution.
Plan and prepare. Determine a known azimuth, and the direction that the calculation will proceed (clockwise or counterclockwise). List the adjusted interior angles of the traverse and draw a sketch of the entire traverse. Be sure it is reasonably accurate (that is, angles and distances should be close to scale). Label the points, the starting direction, and the interior angles. Orient the drawing properly to North.
Step 1
Perform the calculation. Start by writing down the starting azimuth. Add 180° to obtain the back azimuth. Subtract the adjusted interior angle to obtain the azimuth of the next line. If the result is greater than 360, subtract 360. Write down the azimuth on the sketch.
Step 2
Repeat the calculation. For each line of the traverse the same calculation should be repeated. That is, add 180° and subtract the interior angle.
Check the calculations by using the last interior angle to recalculate the starting azimuth.
Example
Step 3
Step 4
Calculate the direction of each line and provide a check (clockwise).
Example Solution