Geomatics Surveying

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Questions and Answers

What is the purpose of including checks in a survey design?

To reduce the frequency of measurements

To detect and prevent errors from going undetected (correct)

To speed up the surveying process

To decrease the precision of the detail measurement

Why is it pointless to measure distances to points of detail to greater precision than 0.25 m at a scale of 1/1000?

Because the scale of the plan does not require that level of precision (correct)

Because the measurements are not necessary for the survey

Because the instruments used cannot measure that accurately

Because it is not possible to measure with that level of precision

What happens to the frequency of errors as experience is gained?

It decreases (correct)

It increases significantly

It remains the same

It becomes impossible to make errors

What is the purpose of measuring the diagonal AD in Figure 1.3?

To check the validity of the measurements Signup and view all the answers

What is the effect of increasing the scale of a plan from 1/1000 to 1/100?

The precision of the detail measurement increases Signup and view all the answers

What is the purpose of designing methods of recording observations and computation?

To show up errors in these processes Signup and view all the answers

What is the benefit of including additional measurements in fieldwork?

It provides checks on the validity of the measurements Signup and view all the answers

Why is it necessary to include checks in a survey?

Because errors can be made in every aspect of surveying Signup and view all the answers

What is the term used to describe directions in land surveying?

Bearing Signup and view all the answers

What is the horizontal angle measured from a given reference point?

Bearing Signup and view all the answers

What is the line passing through the north and south poles of the Earth and the observer's position?

Astronomical meridian Signup and view all the answers

How many main types of bearings are there, depending on the reference direction or meridian used?

Four Signup and view all the answers

What is the bearing measured with respect to the true/geographical/astronomical meridian?

True/Astronomical bearing Signup and view all the answers

What is determined by astronomical observations?

True/geographical/astronomical meridian Signup and view all the answers

What is the center of rotation/angular displacement in measuring bearing?

Observer (O) Signup and view all the answers

What is the term used to describe the reference directions or lines used in surveying for bearings?

Meridians Signup and view all the answers

What is the magnetic bearing of the line recorded on the old survey plan in Example 2?

N34°30'W Signup and view all the answers

What is the annual change in declination in Example 2?

2' eastward Signup and view all the answers

What is the declination in 1970 for the area in Example 2?

10˚00' W Signup and view all the answers

What is the declination in 1910 for the area in Example 2?

12˚00' W Signup and view all the answers

What is the change in declination in 60 years in Example 2?

02˚ 00' (Eastwards +) Signup and view all the answers

What is the magnetic bearing AD in Example 1?

54˚30' E Signup and view all the answers

What is the true bearing in Example 1?

71˚ 53' Signup and view all the answers

What is the change in declination in Example 1?

-7' (westward) Signup and view all the answers

What is the term for the process of determining the position of points relative to others?

Surveying Signup and view all the answers

What is the primary instrument used in theodolite surveying?

Theodolite Signup and view all the answers

What is the purpose of control points in surveying?

To provide a system of horizontal controls Signup and view all the answers

What is the term for the process of estimating the feasibility of a survey project?

Reconnaissance Signup and view all the answers

What is the term for the process of determining the position of points using angles only?

Trigonometry Signup and view all the answers

What is the term for the process of recording and documenting survey measurements?

Booking Signup and view all the answers

What is the instrument used to measure vertical and horizontal distances during Tacheometric surveys?

Theodolite Signup and view all the answers

What is the term for the process of presenting survey data in a graphical format?

Plotting Signup and view all the answers

What does a large closing error indicate?

Faulty chaining or plotting Signup and view all the answers

What is the purpose of adjusting the traverse?

To eliminate the closing error Signup and view all the answers

What is the method of distributing the error called?

The Bowditch adjustment method Signup and view all the answers

What is the direction of the shift in the traverse adjustment?

Parallel to the closing error Signup and view all the answers

What is the purpose of drawing lines parallel to AA' through each plotted station?

To distribute the closing error Signup and view all the answers

What is the result of simply joining E' to A?

A serious displacement and difference in length of the line EA Signup and view all the answers

What is the graphical method used for?

To adjust the traverse Signup and view all the answers

What is the name of the line in Figure 4.2 that represents the closing error?

AA' Signup and view all the answers

Study Notes

Principles of Surveying

To ensure accuracy, measurements should not be taken to a greater precision than can be plotted on the plan
A scale of 1/1000 means distances on the plan are plotted to 0.25 mm, representing 25 cm on the ground, so measurements should not be taken to a greater precision than 0.25 m
A scale of 1/100 means distances on the plan are plotted to 2.5 cm, requiring a greater precision of measurement

Provision of Adequate Checks

Errors can occur in every aspect of surveying, including operating and reading instruments, recording observations, and calculating and plotting results
Errors can be made even with increasing experience, so checks are necessary to detect and prevent them
Checks in fieldwork involve taking extra measurements to fulfill the geometrical requirements of the survey
Comparing measured and plotted values provides a check on the validity of measurements

Basic Terminologies in Compass Surveying

Bearing: the horizontal angle measured clockwise from a given reference point or line
Meridian: a reference direction or line used in surveying for bearings
Types of reference directions (meridians) and bearings:
- True/Astronomical bearing
- Magnetic/Compass bearing
- Grid/Map bearing
- Local/Arbitrary bearing

Compass Surveying

Magnetic bearing: measured with respect to the magnetic north
Declination: the angle between the magnetic and true north
True bearing: calculated from the magnetic bearing and declination

Plotting by Protractor and Scale

A large closing error indicates faulty chaining or plotting
A small closing error can be eliminated by slightly modifying the shape of the polygon and closing the traverse
Adjusting the traverse involves distributing the error around the traverse by shifting each station proportionately to its total distance from the start of the traverse

Types of Errors

Local attraction: an error that can be attributed to local attraction
Causes of errors:
- Faulty chaining or plotting
- Instrumental errors
- Observational errors

Land Survey Terms

Reconnaissance: a preliminary survey to gather information about the area
Station marking: identifying and marking reference points
Control points: reference points used to establish a system of horizontal controls
Control network system: a system of interconnected control points
Direction, distance, and elevation measurements: basic observable quantities necessary in position determination and fixing
Detailing: the process of collecting detailed data about the area
Booking: recording data and information during a survey
Plotting: the process of creating a map or plan from the collected data

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Description

Solve problems involving magnetic bearings, declination, and true bearings in geomatic engineering. Examples include calculating declination in different years and determining true bearings from magnetic bearings.