Traverse correction is a process used by land surveyors to adjust measurements taken during a traverse, which is a series of connected surveying lines or sides. The correction process ensures that the final traverse is accurate and meets the required standards.
There are different methods for traverse correction, including the Transit Rule and the Bowditch Rule. These methods can be implemented in a spreadsheet program like Microsoft Excel to perform the calculations efficiently.
To understand the process of traverse correction in Excel, let's focus on a closed traverse, which is a looped traverse where the starting and ending points are the same. The steps involved are as follows:
Data Entry: Enter the survey data into an Excel spreadsheet. The data typically includes the observed angles, the measured distances, and the coordinates of the traverse stations.
Calculation of Adjusted Angles: Calculate the adjusted angles by summing the observed angles and applying the appropriate correction. In the case of a closed traverse, the sum of the observed angles should be equal to the sum of the interior angles of a polygon, which is (n-2) * 180 degrees for an n-sided polygon.
a. Apply the Transit Rule: According to the Transit Rule, the correction for each angle is calculated as the difference between the sum of observed angles and the sum of interior angles divided by the number of angles. This correction is added to or subtracted from each observed angle.
b. Apply the Bowditch Rule: The Bowditch Rule involves calculating a correction factor (CF) for each angle. The CF for an angle is calculated as the difference between the sum of observed angles and the sum of interior angles divided by the sum of the measured distances. The correction for each angle is then obtained by multiplying the CF by the measured distance for that angle.
Calculation of Adjusted Distances: Calculate the adjusted distances by applying the appropriate corrections to the measured distances. There are different methods for distance corrections, such as the Compass Rule, Transit Rule, and Crandall's Rule, but for simplicity, we will assume the measured distances are already adjusted.
Calculation of Coordinate Corrections: Calculate the coordinate corrections for each traverse station by multiplying the adjusted distances by the cosine and sine of the adjusted angles, respectively.
Calculation of Final Coordinates: Calculate the final coordinates of each traverse station by summing the initial coordinates with the coordinate corrections.
Closure Check: Perform a closure check by comparing the final coordinates of the starting and ending points. If they are not the same or within an acceptable tolerance, further adjustments may be required.
By following these steps and implementing the necessary formulas in Excel, land surveyors can efficiently perform traverse correction for closed traverses using the Transit Rule or the Bowditch Rule.