Chain Surveying Quiz and Flashcards: Chain Line in Surveying

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Questions and Answers

What is the purpose of chain surveying?

Measuring both linear and angular distances

Taking direct measurements using linear measurements only (correct)

Utilizing advanced technology for mapping large areas

Conducting aerial surveys for accurate results

Which equipment is NOT used in chain surveying for slope angle measurement?

Cross staff

Optical squares (correct)

Clinometer

Abney level

What material is commonly used to make chains in chain surveying?

Copper wire

Aluminum wire

Fiber optic cable

Steel wire (correct)

How far apart are the links in a chain typically measured from center to center?

200mm Signup and view all the answers

Which type of chain is specifically mentioned as one of the three different types used in taking measurements?

Engineers chain Signup and view all the answers

What width are steel bands typically used in chain surveying?

$13$mm Signup and view all the answers

What is the purpose of establishing primary triangulation networks?

To provide control for the production of national maps Signup and view all the answers

In the classical triangulation approach, how were base lines typically measured?

By invar tapes in catenary Signup and view all the answers

What was the purpose of roof-top triangulation in urban areas?

To situate control stations on accessible buildings Signup and view all the answers

What is the consequence of an error in the measurement of the base line in the triangulation network?

Scale error throughout the network Signup and view all the answers

How are the remaining sides of triangles found after measuring the base line and adjusted angles?

By mathematical calculations Signup and view all the answers

Why is triangulation best suited for open, hilly country rather than urban areas?

To afford long sights well clear of intervening terrain Signup and view all the answers

What is the purpose of using optical squares in surveying?

Setting out lines at right angles to the main chain line Signup and view all the answers

Which surveying instrument is used for measuring the slope angle of the ground?

Abney Level Signup and view all the answers

How are steel tapes different from linen tapes in surveying?

Steel tapes do not stretch in use, unlike linen tapes Signup and view all the answers

What should be done to chains and steel tapes after using them in wet weather?

Clean the chains and dry the steel tapes with an oily rag Signup and view all the answers

What is the purpose of arrows in surveying?

Marking temporary stations Signup and view all the answers

How are ranging rods commonly marked to ensure visibility?

With red and white bands Signup and view all the answers

Why should linen tapes not be used for work requiring great accuracy?

They are prone to stretching during use Signup and view all the answers

What is the purpose of using pegs in surveying?

Setting out building foundations Signup and view all the answers

What is a Cross Staff used for in surveying?

Setting out lines at right angles to the main chain line Signup and view all the answers

Which material is commonly used for making pegs in surveying?

Wood Signup and view all the answers

What is the purpose of witnessing in a chain survey?

To re-locate a station again even after a long interval Signup and view all the answers

Why should stations, where possible, be tied-in to permanent objects in a chain survey?

To re-locate a station again even after a long interval Signup and view all the answers

What is the main function of check lines in a chain survey?

To save any unnecessary duplication of lines Signup and view all the answers

Why should obstacles such as steep slopes be avoided in selecting survey lines?

To ensure safe and accurate measurements Signup and view all the answers

What is the significance of having well-conditioned triangles in a chain survey?

To provide sharp definition of the stations point Signup and view all the answers

Why should short offsets to survey lines be selected in a chain survey?

To facilitate single-person operations instead of using tape requiring two people Signup and view all the answers

What is the main purpose of ranging during a chain survey?

To get a straight line for marking stations and route Signup and view all the answers

How do gross errors differ from other types of errors in surveying?

They include mistakes due to carelessness or incompetence Signup and view all the answers

What could be a common cause for gross errors on construction sites according to the text?

In-experienced Engineers unfamiliar with equipment and methods Signup and view all the answers

What should always be done with steel bands/tapes when not in use according to the text?

Keep tapes reeled up Signup and view all the answers

What is the main focus of Lecture 11?

Applying corrections to linear measurements Signup and view all the answers

How can systematic errors be eliminated in measurements?

By calibrating the observing equipment Signup and view all the answers

What is the purpose of applying a pull correction in linear measurements?

To account for the extension due to pull Signup and view all the answers

Which type of error is cumulative in effect and has the same magnitude and sign in a series of measurements?

Systematic errors Signup and view all the answers

What method can be adopted to ensure that random errors are kept within acceptable limits?

Increasing the number of observations Signup and view all the answers

When is a sag correction applied in linear measurements?

When there is a catenary curve formed by the tape Signup and view all the answers

What effect does an increase in field temperature have on the recorded length in temperature correction?

+ve error, -ve correction Signup and view all the answers

How are gross errors typically eliminated in surveying?

By carefully observing and constantly checking operations Signup and view all the answers

'At one time, it was easier to measure angles than distances' is mentioned in reference to:

Triangulation Signup and view all the answers

'Statistical principles must be used to analyze variable random errors' is associated with:

Random Errors Signup and view all the answers

What is the purpose of applying a temperature correction in linear measurements?

To adjust for errors caused by temperature differences during measurement Signup and view all the answers

What does a negative error and positive correction signify in the pull correction method?

The recorded length is less than the actual length, requiring an increase in measured value Signup and view all the answers

What should be done to eliminate systematic errors in linear measurements?

Use statistical principles to analyze variable random errors Signup and view all the answers

When is a sag correction typically required in linear measurements?

When measuring lengths over uneven terrain or slopes Signup and view all the answers

What does a positive error and negative correction signify in the pull correction method?

The recorded length is greater than the actual length, requiring a decrease in measured value Signup and view all the answers

Why is it important to apply standard length corrections in linear measurements?

To ensure accurate measurements are taken with standardized equipment Signup and view all the answers

What is a key consideration when selecting the best position for survey stations?

Avoiding angles less than 25° between stations Signup and view all the answers

Why are braced quadrilaterals considered important in surveying?

They provide more conditions of adjustment Signup and view all the answers

When is it advisable to use stereo-pairs of aerial photographs in surveying?

When a three-dimensional view of the terrain is needed Signup and view all the answers

What should be avoided when siting ground-grazing rays between survey stations?

Avoiding positioning them directly opposite each other Signup and view all the answers

Which statement best describes the purpose of referencing a survey station?

To locate it accurately at a future date Signup and view all the answers

Why might signal lamps be preferred as targets in highly precise networks?

To aid in night-time observations with minimal refraction Signup and view all the answers

What method would typically be used to measure the base line and check base in a triangulation network?

Utilizing Electronic Distance Measurement (EDM) Signup and view all the answers

In surveying, what is the benefit of conducting least squares adjustment using the standard variation of coordinates method?

It ensures high accuracy in the survey network Signup and view all the answers

When connecting a survey to the national mapping system, what must be done with baseline measurements?

Reduced to Mean Sea Level (MSL) and scaled up locally Signup and view all the answers

What is the purpose of reciprocal ranging in chain surveying?

To extend the chain line when interrupted by obstacles Signup and view all the answers

How are obstacles like water bodies typically handled in chain surveying?

By using similar triangles to bypass them Signup and view all the answers

Why is compass survey preferred for larger areas compared to chain survey?

It is faster for filling in details in larger surveys Signup and view all the answers

In compass surveying, what is the main function of the prismatic compass?

Measuring magnetic bearings Signup and view all the answers

Why does the text mention that the surveyor's compass is generally more accurate than the prismatic compass?

It aligns itself to the earth's magnetic field more accurately Signup and view all the answers

What precaution should be taken when using a compass survey due to magnetic disturbances?

Ensure that no metallic objects are near the compass Signup and view all the answers

What is the purpose of extending the chain line up to point R when obstructed by a jungle area?

To bypass the jungle obstacle using a random line PT Signup and view all the answers

'Compass surveys are mainly used for rapid filling of detail in larger surveys and for explanatory works' - Why may this be the case?

Compass surveys are faster and efficient for larger areas Signup and view all the answers

How do prismatic compasses differ from surveyor's compasses according to the text?

Prismatic compasses are smaller and portable while surveyor's compasses are larger Signup and view all the answers

Why should care be taken to ensure magnetic disturbances are not present during compass surveys?

To prevent errors in magnetic measurements Signup and view all the answers

Why were primary trig points usually fixed at the tops of mountains in triangulation networks?

To maximize the accuracy of measured angles Signup and view all the answers

In triangulation networks, what was the purpose of establishing secondary networks with sides of 10–20 km?

To facilitate connection to primary triangles Signup and view all the answers

Why is roof-top triangulation used in urban areas?

To overcome obstacles and have clear sight lines Signup and view all the answers

What is the significance of measuring check base lines in a triangulation network?

To control scale error in the network Signup and view all the answers

How would scale error impact a triangulation network if there is an error in the measurement of the base line?

It would result in scale error throughout the network Signup and view all the answers

Why is roof-top triangulation suitable for urban areas?

To overcome obstacles such as buildings Signup and view all the answers

What is the main goal of establishing primary triangulation networks?

To provide long sight lines for measuring angles Signup and view all the answers

Why was it essential to establish third and fourth-order nets in triangulation networks?

To increase control at closer intervals Signup and view all the answers

Why is triangulation best suited to open, hilly country rather than urban areas?

To provide long, clear sight lines for measurements Signup and view all the answers

What is a modern approach to measuring base lines in triangulation networks?

Including many more measured lines to control scale error Signup and view all the answers

What is the purpose of the prism in a prismatic compass?

To magnify the image of the compass graduations Signup and view all the answers

Which component of a prismatic compass helps prevent damage to the pivot point?

Lifting pin and lifting lever Signup and view all the answers

In a prismatic compass, where is the object vane located?

Opposite to the prism Signup and view all the answers

What is the purpose of the reflecting mirror in a prismatic compass?

To get images of objects above or below the instrument level Signup and view all the answers

What is the function of the graduated ring in a prismatic compass?

To measure angles of lines from magnetic meridian Signup and view all the answers

Why is the mirror located in front of the forward vane slid up and down?

For solar observations or viewing very high objects Signup and view all the answers

What does the eye vane do in a prismatic compass?

Bisects objects from a fine slit with an eye hole at bottom Signup and view all the answers

What is the function of the glass cover in a prismatic compass?

Shows needle and graduated ring from the top Signup and view all the answers

How does a prismatic compass differ from a surveyor's compass in terms of graduation direction?

Prismatic compass graduations run clockwise from south Signup and view all the answers

Why are dark glasses swung in front of the back vane in a prismatic compass?

Used when some luminous objects are being bisected Signup and view all the answers

What is the purpose of using the spring brake or brake pin in a prismatic compass?

To damp the needle's oscillation before taking a reading Signup and view all the answers

How is centering checked in a prismatic compass?

By dropping a small pebble from the compass Signup and view all the answers

What is the purpose of levelling the compass in surveying?

To achieve a proper level of the compass Signup and view all the answers

What does the magnetic bearing of a survey line represent?

The angle between the direction of the line and the magnetic meridian Signup and view all the answers

What causes the largest variation in magnetic declination?

Secular Variation Signup and view all the answers

What is the angle of declination in surveying?

The angle between true north and magnetic north Signup and view all the answers

How can the magnetic meridian be defined?

As a line along the direction of a freely supported magnetized needle Signup and view all the answers

What is the main function of a surveyor's compass?

To determine magnetic bearings of lines Signup and view all the answers

What does the diurnal variation refer to in terms of magnetic declination?

A minor variation during specific time frames like weeks or lunar months Signup and view all the answers

What is meant by focusing in relation to a prismatic compass?

Moving prisms till graduations are clearly visible Signup and view all the answers

What is the main difference between true bearing and magnetic bearing?

True bearing is measured with respect to true north, while magnetic bearing is measured with respect to magnetic north. Signup and view all the answers

When converting whole circle bearing to reduced bearing, which quadrant does the line lie in if the reduced bearing equals the whole circle bearing?

South-East Signup and view all the answers

In the Quadrantal Bearing System, how are survey lines designated?

Measured with respect to the north or south line closest, either clockwise or counterclockwise. Signup and view all the answers

What is the general rule for determining back bearing from fore bearing?

Add 180 degrees if fore bearing is less than 180 degrees. Signup and view all the answers

In a compass survey, what does a back bearing serve as?

A check to ensure accuracy in measurements. Signup and view all the answers

How can a magnetic bearing be converted into a whole circle bearing?

By adding 180 degrees if it's greater than 180 degrees. Signup and view all the answers

Which quadrant would a line fall into if its reduced bearing is 45 degrees?

North-East Signup and view all the answers

What is the significance of taking both fore and back bearings during traversing with a compass?

To allow for error detection and correction. Signup and view all the answers

Study Notes

Chain Surveying

The purpose of chain surveying is to measure distances and angles between survey stations.
Chains are not used to measure slope angles.
Chains are typically made of steel or linen material.
Links in a chain are usually measured from center to center, with a typical distance of 20-30 mm apart.
There are three types of chains used in taking measurements: steel band, linen tape, and steel tape.

Triangulation

The purpose of establishing primary triangulation networks is to provide a framework for mapping.
Base lines are typically measured using a high degree of accuracy.
Roof-top triangulation was used in urban areas to overcome obstacles.
An error in the measurement of the base line has a significant consequence on the entire triangulation network.
Remaining sides of triangles are found by measuring the base line and adjusted angles.

Surveying Equipment

Optical squares are used for taking accurate right angles.
A clinometer is used for measuring the slope angle of the ground.
Steel tapes differ from linen tapes in terms of their materials and uses.
Chains and steel tapes should be cleaned and dried after use in wet weather.
Arrows are used to mark survey lines for visibility.
Ranging rods are commonly marked with flags or reflective material for visibility.

Pegs and Cross Staff

Pegs are used to mark survey stations, and are typically made of wood or metal.
A Cross Staff is used for aligning and leveling survey instruments.
Witnessing is done to verify the location of survey stations.

Check Lines and Errors

Check lines are used to verify the accuracy of survey lines.
Gross errors differ from other types of errors in that they are usually large and obvious.
Systematic errors can be eliminated by applying corrections to measurements.
Random errors can be minimized by taking multiple measurements and applying statistical principles.

Temperature Correction

Temperature correction is applied to linear measurements to account for changes in tape length due to temperature changes.
A sag correction is applied when there is a significant difference in elevation between the two ends of a measurement.

Survey Stations

Survey stations should be tied-in to permanent objects whenever possible.
The purpose of ranging is to establish a chain of measurements between survey stations.
Braced quadrilaterals are used to provide additional accuracy and stability to survey networks.

Aerial Photographs and Ground-Grazing Rays

Stereo-pairs of aerial photographs are used to obtain accurate measurements in areas with obstacles.
Signal lamps are preferred as targets in highly precise networks due to their visibility.

Least Squares Adjustment

The benefit of conducting least squares adjustment is to minimize errors and obtain the most accurate results.

National Mapping System

When connecting a survey to the national mapping system, baseline measurements must be tied-in to the national grid.

Compass Surveying

Compass surveying is preferred for larger areas due to its speed and ease of use.
The main function of the prismatic compass is to measure directions and bearings.
Care should be taken to avoid magnetic disturbances during compass surveys.

Triangulation Networks

Primary trig points were usually fixed at the tops of mountains in triangulation networks.
Secondary networks were established with sides of 10-20 km to provide additional accuracy.
Roof-top triangulation was used in urban areas to overcome obstacles.
Triangulation is best suited to open, hilly country rather than urban areas due to the ease of establishing survey stations.

Prismatic Compass

The prism in a prismatic compass is used to measure angles and directions.
The object vane is located in front of the prism.
The reflecting mirror is used to view the object vane.
The graduated ring measures the angle of rotation.
The mirror is located in front of the forward vane and slid up and down to view the object vane.
The eye vane is used to view the object vane.
The glass cover protects the prism and mirror.
The spring brake or brake pin is used to prevent damage to the pivot point.

Levelling and Magnetic Declination

Leveling is essential in surveying to ensure accurate measurements.
The magnetic bearing of a survey line represents the direction relative to the magnetic north.
The angle of declination is the difference between the magnetic and true bearings.
The magnetic meridian is an imaginary line that passes through the magnetic north.
The main function of a surveyor's compass is to measure directions and bearings.
Diurnal variation refers to the daily change in magnetic declination.

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Description

Explore the equipment used in chain surveying, the simplest form of land surveying utilizing linear measurements. Learn about tools for linear measurement, slope angle measurement, and measuring right angles.

Lecture 8 Chain Surveying Equipment

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