Podcast
Questions and Answers
What is the purpose of including checks in a survey design?
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?
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?
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?
What is the purpose of measuring the diagonal AD in Figure 1.3?
What is the effect of increasing the scale of a plan from 1/1000 to 1/100?
What is the effect of increasing the scale of a plan from 1/1000 to 1/100?
What is the purpose of designing methods of recording observations and computation?
What is the purpose of designing methods of recording observations and computation?
What is the benefit of including additional measurements in fieldwork?
What is the benefit of including additional measurements in fieldwork?
Why is it necessary to include checks in a survey?
Why is it necessary to include checks in a survey?
What is the term used to describe directions in land surveying?
What is the term used to describe directions in land surveying?
What is the horizontal angle measured from a given reference point?
What is the horizontal angle measured from a given reference point?
What is the line passing through the north and south poles of the Earth and the observer's position?
What is the line passing through the north and south poles of the Earth and the observer's position?
How many main types of bearings are there, depending on the reference direction or meridian used?
How many main types of bearings are there, depending on the reference direction or meridian used?
What is the bearing measured with respect to the true/geographical/astronomical meridian?
What is the bearing measured with respect to the true/geographical/astronomical meridian?
What is determined by astronomical observations?
What is determined by astronomical observations?
What is the center of rotation/angular displacement in measuring bearing?
What is the center of rotation/angular displacement in measuring bearing?
What is the term used to describe the reference directions or lines used in surveying for bearings?
What is the term used to describe the reference directions or lines used in surveying for bearings?
What is the magnetic bearing of the line recorded on the old survey plan in Example 2?
What is the magnetic bearing of the line recorded on the old survey plan in Example 2?
What is the annual change in declination in Example 2?
What is the annual change in declination in Example 2?
What is the declination in 1970 for the area in Example 2?
What is the declination in 1970 for the area in Example 2?
What is the declination in 1910 for the area in Example 2?
What is the declination in 1910 for the area in Example 2?
What is the change in declination in 60 years in Example 2?
What is the change in declination in 60 years in Example 2?
What is the magnetic bearing AD in Example 1?
What is the magnetic bearing AD in Example 1?
What is the true bearing in Example 1?
What is the true bearing in Example 1?
What is the change in declination in Example 1?
What is the change in declination in Example 1?
What is the term for the process of determining the position of points relative to others?
What is the term for the process of determining the position of points relative to others?
What is the primary instrument used in theodolite surveying?
What is the primary instrument used in theodolite surveying?
What is the purpose of control points in surveying?
What is the purpose of control points in surveying?
What is the term for the process of estimating the feasibility of a survey project?
What is the term for the process of estimating the feasibility of a survey project?
What is the term for the process of determining the position of points using angles only?
What is the term for the process of determining the position of points using angles only?
What is the term for the process of recording and documenting survey measurements?
What is the term for the process of recording and documenting survey measurements?
What is the instrument used to measure vertical and horizontal distances during Tacheometric surveys?
What is the instrument used to measure vertical and horizontal distances during Tacheometric surveys?
What is the term for the process of presenting survey data in a graphical format?
What is the term for the process of presenting survey data in a graphical format?
What does a large closing error indicate?
What does a large closing error indicate?
What is the purpose of adjusting the traverse?
What is the purpose of adjusting the traverse?
What is the method of distributing the error called?
What is the method of distributing the error called?
What is the direction of the shift in the traverse adjustment?
What is the direction of the shift in the traverse adjustment?
What is the purpose of drawing lines parallel to AA' through each plotted station?
What is the purpose of drawing lines parallel to AA' through each plotted station?
What is the result of simply joining E' to A?
What is the result of simply joining E' to A?
What is the graphical method used for?
What is the graphical method used for?
What is the name of the line in Figure 4.2 that represents the closing error?
What is the name of the line in Figure 4.2 that represents the closing error?
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.
