Compass Surveying - Problem No 3 ( Included Angles & Error Correction of a Closed Traverse )

Summary

This video script offers a detailed tutorial on correcting forbearing and back bearings in a traverse survey with suspected local attraction. It explains the concept of whole circle bearings and demonstrates the process of drawing a traverse with given bearings. The script guides through calculating included angles, adjusting for errors, and determining corrected bearings to ensure the difference between forbearing and back bearing is 180 degrees, concluding with a verification of the calculations.

Takeaways

• 📐 The script discusses a problem in Commerce surveying involving traversing with bearings and correcting for local attraction.
• 🧭 The bearings are given in whole circle bearing, which is measured clockwise from the north point of the meridian.
• 📝 The process begins by drawing the traverse with direction symbols based on the given four bearings.
• 🔍 The back bearings are the reverse of the forbearings and are used to verify the accuracy of the traverse drawing.
• 🔢 The included angles are calculated by finding the interior angles of the traverse, which are essential for correcting the bearings.
• ⚖️ The sum of the observed angles is compared with the theoretical sum to find the error and apply corrections to each station.
• 🔄 The correction for each station is determined by dividing the total error by the number of stations involved.
• 🛠 The corrected interior angles are used to find the corrected four bearings and back bearings for each line.
• 🔄 The difference between the four bearing and back bearing should be 180 degrees, except for the special case of BC where it is 360 - 180 = 180 degrees.
• 📉 The script provides a step-by-step method to calculate and verify the corrected bearings, ensuring accuracy in surveying.
• 👍 The final step confirms the correctness of the calculations by checking that the corrected bearings meet the expected criteria.

Q & A

What is the first step in solving the problem based on commerce surveying?

The first step is to read the question and understand the given four and back bearings observed in traversing with a canvas in a place where local attraction was suspected.

How are whole circle bearings measured?

Whole circle bearings are measured as the horizontal angle clockwise from the North Point of the meridian.

How do you determine the direction of the bearings on the traverse?

You start by drawing the direction symbol at each station and indicate the bearings based on the given angles, ensuring they align with the corresponding degrees for North, East, South, and West.

What is the significance of back bearings in this context?

Back bearings are the reverse of forebearings, and they are used to check the accuracy of the drawing and calculations.

How do you verify the correctness of the back bearings?

You verify the correctness by comparing the back bearings with the corresponding forebearings and ensuring the differences match the expected values.

What are included angles, and how are they calculated in the traverse?

Included angles are the interior angles of the traverse. They are calculated by subtracting the given angles at each station to determine the precise measurements.

How do you calculate the sum of observed angles, and why is it important?

The sum of observed angles is calculated by adding all the interior angles. It is important for ensuring the traverse closure and identifying any errors.

What is the formula for the theoretical sum of the angles, and how is it used?

The formula for the theoretical sum of the angles is (2N - 4) * 90, where N is the number of stations. It is used to compare with the observed sum to identify any errors.

How do you find the correction for each station if there is an error?

You find the correction for each station by dividing the total error by the number of stations and applying the correction to each angle.

How do you find the corrected bearings after determining the included angles and corrections?

You find the corrected bearings by using the corrected included angles and applying the necessary adjustments to the initial forebearings and back bearings.