Surveying Techniques and Errors

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Questions and Answers

What is the definition of a true meridian?

A fixed line passing through the poles. (correct)

A parallel to the central meridian of a coordinate system.

A reference line taking convenience into account.

A line that lies parallel to magnetic lines of force.

Which reading reflects a higher elevation when comparing rod readings at points A and B?

Rod reading at point A for a level sight.

Rod reading at point B for a level sight. (correct)

Rod reading at point A plus reading from Set Up Instrument.

Rod reading at point B minus reading from Set Up Instrument.

What must be assessed to determine if the line of sight needs further adjustment in the two-peg test?

The total elevation difference between points A and B.

The difference in rod readings between setup A and B. (correct)

The average of rod readings from both setups.

The rod readings taken at the midpoint.

What would be the appropriate next step if the false difference in elevation is found to be significant?

Repeat the two-peg test procedure. Signup and view all the answers

When determining angles to the right, how is the angle measured?

Clockwise from the preceding line. Signup and view all the answers

What is the proper definition of bearings in surveying?

The acute horizontal angle between a reference meridian and a line. Signup and view all the answers

In a closed polygon surveying, what should the sum of all deflection angles equal?

360 degrees. Signup and view all the answers

What is the significance of adjusting rod readings during a peg adjustment survey?

To ensure accuracy in elevation when the instrument is set up. Signup and view all the answers

What is the primary use of reciprocal leveling?

To leveling across considerable distances where traditional methods cannot be employed Signup and view all the answers

Which formula is correctly associated with trigonometric leveling?

DE = dtan θ + HI - RR Signup and view all the answers

In rise and fall leveling, what principle does the method rely on?

Two consecutive readings from the same position to find elevation differences Signup and view all the answers

What correction must be applied if the horizontal distance exceeds 300 meters in trigonometric leveling?

0.067(d/1000)2 Signup and view all the answers

Which is a key characteristic of profile leveling?

It determines elevation differences at specified short intervals. Signup and view all the answers

What is the primary goal of measuring angles in leveling?

To determine the difference in elevation vertically Signup and view all the answers

In the context of leveling, what does 'HI' stand for?

Height of Instrument Signup and view all the answers

What is NOT a suitable application for trigonometric leveling?

Determining close range elevation difference at short intervals Signup and view all the answers

Which type of compass traverse does not return to its starting point?

Open Compass Traverse Signup and view all the answers

Which source of error is commonly caused by the compass box being affected by nearby magnetic fields?

Local Attraction Signup and view all the answers

What is the correct formula for determining the index error in vertical angle measurements?

Ie = (θn - θr)/2 Signup and view all the answers

When adjusting line of sight, which condition must be maintained to ensure accurate measurements?

The line of sight must be parallel to the level tube. Signup and view all the answers

In the adjustment of a closed compass traverse, which of the following measurements confirms the traverse's accuracy?

The sum of the bearings must equal 360 degrees. Signup and view all the answers

What is the primary purpose of measuring angles by repetitions?

To gain better accuracy in measurements. Signup and view all the answers

Which of the following is NOT a possible error source in compass work?

Excessive Wind Speed Signup and view all the answers

In the example of adjusting an open compass traverse, what does the angle N 25° 45' E signify?

A bearing measured clockwise from north. Signup and view all the answers

Study Notes

Two-Peg Test

The two-peg test is used to determine the true difference in elevation between points.
It also checks if the line of sight needs further adjustment.
The test involves setting up a dumpy level near two points, A and B.
Readings are taken on both points with the instrument in both the near A and near B positions.

Peg Adjustment

This procedure involves setting up a wye level at two points, 1 and 2.
The rod readings at points A and B are taken at each instrument position.
Point 1 is midway between A and B.
Point 2 is further from A and B.
The correct rod reading at point A for a level sight can be calculated using the readings taken at point 2.

Compass Surveying

Compass surveying is used to determine the relative locations of points when high precision is not required.
It involves measuring bearings and angles using a compass.
There are two main types of compass traverses: open and closed.

Sources of Errors in Compass Work

Several factors can contribute to errors in compass work.
These include bent needle, bent pivot, sluggish needle, plane of sight not vertical, electrically charged compass box, local attraction, magnetic variations, and errors in reading the needle.

Adjustment of Compass Traverses

Open and closed compass traverses require specific adjustments to minimize errors.
The adjustment process involves calculating the errors in each bearing and then adjusting the bearings accordingly.

Index Error and Correction

Index error is the difference between the observed vertical angle and the actual vertical angle.
It can occur due to inclination of the vertical axis, misalignment of the level tube, and the vertical circle not reading zero when the telescope bubble is centered.
The index correction is the same magnitude as the index error but has the opposite sign.

Measurement of Angles by Repetitions

This method is used to improve the accuracy of angle measurements.
It involves measuring the angle multiple times and taking the average.

Leveling Techniques

Stadia Leveling: Used to determine elevations by measuring the difference in rod readings.
Reciprocal Leveling: Used to determine elevation differences between two distant points.
Profile Leveling: Used to create a vertical profile of a line by measuring elevations at designated intervals.
Trigonometric Leveling: Used to determine elevation differences using horizontal distances, vertical angles, and trigonometric calculations.
Rise and Fall Leveling: Based on the principle that the difference in elevation between two points is the difference in rod readings taken from the same instrument position.

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Description

This quiz covers various surveying techniques, including the two-peg test, peg adjustment, and compass surveying methods. Additionally, it discusses potential sources of errors in compass work to enhance understanding of field practices. Test your knowledge on these essential surveying concepts.