Top 50 Interview Questions on Compass Surveying

Introduction:

Welcome to the ultimate resource for aspiring surveyors! Whether you’re a seasoned professional or just starting your surveying journey, mastering the top interview questions on compass surveying is crucial for career advancement. In this article, we’ll delve into the intricacies of compass surveying, providing concise and expertly-crafted answers to the top 50 questions that could shape your career trajectory.

1. What is compass surveying?

   • Answer: Compass surveying is a method of surveying in which the direction of survey lines is determined with the help of a magnetic compass.

2. What are the types of compasses used in surveying?

   • Answer: Theodolite compass, prismatic compass, and surveyor’s compass.

3. Explain the working principle of a magnetic compass.

   • Answer: A magnetic compass works based on the principle that a freely suspended magnet aligns itself in the north-south direction due to the Earth’s magnetic field.

4. What is the purpose of a surveyor’s compass?

   • Answer: A surveyor’s compass is used for measuring the magnetic bearing of a line.

5. Differentiate between magnetic bearing and true bearing.

   • Answer: Magnetic bearing is the angle between the magnetic north and the survey line, while true bearing is the angle between the true north and the survey line.

6. What is magnetic declination?

   • Answer: Magnetic declination is the angle between the magnetic north and true north at a specific location.

7. How is magnetic declination applied in compass surveying?

   • Answer: Magnetic declination is used to convert magnetic bearing to true bearing (or vice versa) by adding or subtracting the declination angle.

8. Explain the process of traversing using a compass.

   • Answer: Traversing involves measuring and recording the magnetic bearings of a series of connected survey lines.

9. What is a fore-bearing and back-bearing?

   • Answer: Fore-bearing is the magnetic bearing of a line measured in the direction of survey, while back-bearing is the magnetic bearing measured in the opposite direction.

10. How do you correct for local attraction in compass surveying?

    • Answer: Local attraction can be corrected by comparing bearings from different stations or using a reference line.

11. What is a magnetic meridian?

    • Answer: The line along which a freely suspended magnet aligns itself, indicating the magnetic north, is known as the magnetic meridian.

12. Explain the importance of a check line in compass surveying.

    • Answer: A check line is a line surveyed separately to verify the accuracy of the compass survey; it helps detect errors in measurements.

13. What is the purpose of a prismatic compass in surveying?

    • Answer: A prismatic compass is used for measuring magnetic bearings with greater accuracy than a surveyor’s compass.

14. How do you measure the dip angle using a compass?

    • Answer: The dip angle is measured by tilting the compass needle until it becomes horizontal, and the angle is read off the graduated circle.

15. Explain the procedure for measuring a magnetic bearing with a theodolite compass.

    • Answer: Set up the theodolite, level it, align the telescope with the line, and read the magnetic bearing from the graduated circle.

16. What is the purpose of a vernier compass?

    • Answer: A vernier compass is used for more precise measurement of magnetic bearings and angles.

17. How is a compass survey affected by magnetic storms?

    • Answer: Magnetic storms can cause disturbances in the Earth’s magnetic field, affecting the accuracy of compass readings.

18. Describe the process of adjusting a compass survey.

    • Answer: Adjusting a compass survey involves applying corrections for magnetic declination, local attraction, and instrumental errors.

19. What is the role of a base line in compass surveying?

    • Answer: The base line is a reference line used as a starting point for a survey; it provides a known direction for subsequent measurements.

20. How do you calculate the included angle between two survey lines?

    • Answer: Subtract the back-bearing of the first line from the fore-bearing of the second line.

21. Explain the term “meridian” in the context of compass surveying.

    • Answer: A meridian is an imaginary line passing through the geographical North and South Poles, and it is used as a reference for measuring angles in surveying.

22. What precautions should be taken when using a compass in the field?

    • Answer: Keep the compass away from metallic objects, power lines, and magnetic influences; ensure it is properly leveled before taking readings.

23. Define the term “traverse” in surveying.

    • Answer: A traverse is a series of connected survey lines used to establish control points and measure distances and angles.

24. How do you calculate the length of a survey line using a compass?

    • Answer: Measure the magnetic bearing and the distance along the line, then use trigonometry to calculate the horizontal and vertical components.

25. What is the purpose of a declination diagram in compass surveying?

    • Answer: A declination diagram is a graphical representation of magnetic declination at a specific location, helping in the conversion of magnetic bearings to true bearings.

26. Explain the concept of magnetic dip in compass surveying.

    • Answer: Magnetic dip is the angle between the magnetic meridian and the horizontal plane.

27. How do you find the true meridian using a compass and a known line?

    • Answer: Measure the magnetic bearing of the known line, apply the magnetic declination, and the resulting angle is the true bearing.

28. What are the advantages of using a theodolite compass over a surveyor’s compass?

    • Answer: Theodolite compasses offer greater precision, have a telescope for accurate sighting, and can measure both horizontal and vertical angles.

29. How does the curvature of the Earth affect compass surveying measurements?

    • Answer: Over long distances, the curvature of the Earth can cause discrepancies in compass survey measurements, and corrections may be needed.

30. Describe the process of magnetic compass adjustment.

    • Answer: Adjustments involve correcting for errors such as collimation error, eccentricity error, and scale error to ensure accurate readings.

31. What is the purpose of a prismatic compass clinometer in surveying?

    • Answer: A prismatic compass clinometer is used for measuring both magnetic bearings and vertical angles, providing comprehensive survey data.

32. How does the latitude of a location affect magnetic declination?

    • Answer: Magnetic declination varies with latitude, and charts or models are used to determine the declination at a specific location.

33. Explain the concept of a magnetic dip circle.

    • Answer: A magnetic dip circle is an instrument used to measure the magnetic dip angle at a particular location.

34. What precautions should be taken during compass surveying in hilly or mountainous terrain?

    • Answer: Correct for the effects of slopes and ensure the compass is level; use vertical angles to account for changes in elevation.

35. How do you measure the azimuth of a line using a compass?

    • Answer: Measure the magnetic bearing of the line, adjust for magnetic declination, and the result is the azimuth.

36. Define the term “traverse leg” in compass surveying.

    • Answer: A traverse leg is a segment of a traverse line between two consecutive survey stations.

37. What is the purpose of a declination plate on a compass?

    • Answer: A declination plate is used to set the magnetic declination on a compass, ensuring accurate readings in the field.

38. Explain the role of auxiliary bearings in compass surveying.

    • Answer: Auxiliary bearings are additional magnetic bearings measured to verify or adjust the accuracy of the main traverse.

39. How can you determine the rate of march in compass surveying?

    • Answer: The rate of march is calculated by dividing the distance traveled by the time taken, helping to estimate progress in the field.

40. What are the challenges of compass surveying in areas with high iron deposits?

    • Answer: High iron deposits can cause local attraction, affecting the accuracy of compass readings, and corrections or relocations may be necessary.

41. Describe the use of a declination correction sheet in compass surveying.

    • Answer: A declination correction sheet provides information on magnetic declination at various locations, aiding in the adjustment of compass readings.

42. How do you calculate the closing error in a compass traverse?

    • Answer: The closing error is calculated by finding the difference between the sum of fore-bearings and the sum of back-bearings.

43. What is a traverse adjustment, and why is it necessary?

    • Answer: A traverse adjustment involves distributing errors evenly to improve the overall precision of the survey; it is necessary for accurate mapping.

44. How does the altitude of a location affect magnetic declination?

    • Answer: Magnetic declination is influenced by altitude, and corrections may be required for accurate compass readings at higher elevations.

45. Explain the use of a declination bar in compass surveying.

    • Answer: A declination bar is a movable bar on a compass used to set the magnetic declination, ensuring accurate bearings are measured.

46. What is the significance of a meridian convergence angle in compass surveying?

    • Answer: The meridian convergence angle is the angle between the grid north and true north, and it is considered when converting grid bearings to true bearings.

47. Describe the process of measuring magnetic inclination using a dip needle.

    • Answer: A dip needle is tilted until the needle is horizontal, and the inclination angle is read off the graduated scale.

48. How do you calculate the magnetic length of a survey line?

    • Answer: The magnetic length is calculated by multiplying the true length of the line by the cosine of the magnetic inclination angle.

49. What is a prismatic compass survey, and when is it preferred over other compass surveys?

    • Answer: A prismatic compass survey involves using a prismatic compass to measure magnetic bearings; it is preferred for its accuracy and versatility in varying terrains.

50. Explain the impact of temperature on compass readings and how it can be mitigated.

    • Answer: Temperature can affect the performance of a compass; adjustments should be made for extreme temperatures, and the compass should be allowed to acclimate before use.

51. What is the purpose of a transit compass in surveying, and how does it differ from a standard compass?

    • Answer: A transit compass is designed for more accurate angular measurements and is equipped with a telescope. It provides precise readings of both horizontal and vertical angles, making it suitable for detailed surveys.

52. Explain the role of a declinometer in compass surveying.

    • Answer: A declinometer is an instrument used to measure the magnetic declination at a specific location. It helps surveyors adjust their compass readings for accurate navigation.

53. How does the time of day influence compass surveying, especially during sunrise or sunset?

    • Answer: During sunrise or sunset, the horizontal component of the Earth’s magnetic field becomes significant, affecting compass readings. Surveyors should be cautious and take readings when conditions are stable.

54. What are the advantages of using a gyrocompass in surveying, and when is it preferred over a magnetic compass?

    • Answer: A gyrocompass is not influenced by magnetic fields and provides stable readings even in areas with high magnetic interference. It is preferred in locations where magnetic compasses may be unreliable.

55. Explain the significance of magnetic dip in compass surveys conducted near the magnetic poles.

    • Answer: Near the magnetic poles, the magnetic dip becomes nearly vertical, making compass needles unreliable. Surveyors must use alternative methods or instruments designed for such extreme conditions.

56. Describe the process of orienting a compass traverse with reference to a known line.

    • Answer: Orienting a compass traverse involves aligning the compass with a known line. Measure the magnetic bearing of the known line, adjust for declination, and set the compass in that direction.

57. How can GPS technology complement compass surveying, and what are the limitations of relying solely on GPS?

    • Answer: GPS technology can provide accurate positional data, aiding in survey control points. However, it may be affected by satellite visibility, signal interference, or atmospheric conditions, emphasizing the importance of traditional survey methods.

58. What steps can be taken to minimize errors introduced by atmospheric conditions in compass surveying?

    • Answer: Atmospheric conditions can affect compass readings. Minimize errors by conducting surveys in calm weather, away from sources of electrical interference, and at times when atmospheric conditions are stable.

59. Explain the term “needle oscillation” in the context of compass surveying.

    • Answer: Needle oscillation refers to the back-and-forth movement of the compass needle when settling at a new bearing. Surveyors should wait for the needle to stabilize before recording readings.

60. How does the inclination of a compass needle change when moving from the equator to the poles?

    • Answer: At the equator, the needle is nearly horizontal, while near the poles, it becomes nearly vertical. This change is due to the varying magnetic inclination along the Earth’s surface.

61. What role does a declination screw play in a compass, and how is it used?

    • Answer: The declination screw allows surveyors to adjust the compass for magnetic declination. By turning the screw, the needle aligns with the true north, compensating for the declination.

62. Describe the importance of magnetic dip correction in compass surveying.

    • Answer: Magnetic dip correction is essential to account for the inclination of the magnetic field. It ensures that compass readings are accurate, especially in areas where the dip is significant.

63. How can the effect of topography on compass readings be minimized during field surveys?

    • Answer: Level the compass carefully to reduce errors introduced by sloping terrain. Adjustments for topographical features can be made by considering both horizontal and vertical angles.

64. Explain the difference between a surveyor’s compass and a prismatic compass in terms of design and functionality.

    • Answer: A surveyor’s compass is a simple compass with a freely rotating magnetic needle, while a prismatic compass has a prism to read bearings directly. Prismatic compasses are generally more accurate.

65. What precautions should be taken when using a compass near electronic devices or power lines?

    • Answer: Electronic devices and power lines can interfere with compass readings. Maintain a safe distance from such sources to ensure accurate measurements.

66. How can the accuracy of compass readings be verified or cross-checked in the field?

    • Answer: Cross-check compass readings by taking auxiliary bearings or by comparing measurements with other surveying instruments to ensure consistency and accuracy.

67. Explain the concept of magnetic intensity and its impact on compass readings.

    • Answer: Magnetic intensity refers to the strength of the Earth’s magnetic field. Higher magnetic intensity can lead to quicker needle oscillation, and surveyors should account for this in their measurements.

68. Describe the process of measuring magnetic inclination using a dip circle.

    • Answer: A dip circle consists of a horizontal graduated circle and a vertical needle. The angle between the needle and the horizontal plane gives the magnetic inclination.

69. What is the purpose of using a declination card in compass surveying, and how is it applied in the field?

    • Answer: A declination card provides a quick reference for the magnetic declination at a specific location. It is set on the compass to ensure accurate readings by accounting for the local declination.

70. Explain how the alignment of survey lines along a magnetic meridian is achieved during compass surveys.

    • Answer: Survey lines are aligned along a magnetic meridian by using a compass to measure the magnetic bearing. Corrections are applied to account for declination, ensuring alignment with the true meridian.

71. What is the impact of a non-level compass on survey measurements, and how can it be corrected?

    • Answer: A non-level compass can introduce errors in both horizontal and vertical angles. To correct, ensure the compass is properly leveled using the built-in bubble level before taking measurements.

72. Explain the process of resection in compass surveying.

    • Answer: Resection involves determining the observer’s position by sighting and measuring angles to three or more known points. The intersection of these lines defines the observer’s location.

73. What are the advantages and disadvantages of using a prismatic compass compared to a theodolite compass?

    • Answer: A prismatic compass is portable and easy to use but may lack the precision of a theodolite compass. Theodolite compasses offer greater accuracy but can be bulkier.

74. How does the accuracy of compass surveying differ in dense forested areas compared to open fields?

    • Answer: In dense forests, magnetic interference from vegetation may impact compass readings. Open fields typically provide more accurate readings, but precautions should still be taken.

75. What is the purpose of a compass traverse closure, and how is it calculated?

    • Answer: A compass traverse closure checks the accuracy of survey measurements. It is calculated by finding the difference between the sum of fore-bearings and the sum of back-bearings.

76. Explain the term “meridian convergence” and its effect on compass surveying in different regions.

    • Answer: Meridian convergence is the angular difference between true north and grid north. It affects compass surveys when converting between grid bearings and true bearings.

77. Describe the process of measuring magnetic intensity in the field.

    • Answer: Magnetic intensity is typically measured using a magnetometer in the field. The instrument provides readings that reflect the strength of the Earth’s magnetic field.

78. How does the latitude of a location influence the magnetic dip angle, and why is it important in compass surveying?

    • Answer: Magnetic dip angle increases with latitude. It is important in compass surveying as it affects the inclination of the compass needle, requiring corrections for accurate readings.

79. What is the role of an azimuth circle in compass surveying, and how is it used?

    • Answer: An azimuth circle is a graduated circle attached to a compass. It allows surveyors to measure or set azimuth angles directly, providing precise directional information.

80. Explain the impact of magnetic storms on compass readings and the precautions that should be taken during such events.

    • Answer: Magnetic storms can cause rapid and erratic needle movements. During such events, surveyors should avoid taking measurements and wait for stable conditions to resume surveys.

81. What are the factors to consider when selecting a compass for a specific surveying task?

    • Answer: Factors include the accuracy required, terrain characteristics, the need for portability, and the potential for magnetic interference in the survey area.

82. Describe the process of measuring magnetic declination using a prismatic compass.

    • Answer: Measure the magnetic bearing of a known line with the prismatic compass, then apply the correction for the observed declination to obtain the true bearing.

83. What is the purpose of a declination diagram in compass surveying, and how is it created?

    • Answer: A declination diagram visually represents magnetic declination at different locations. It is created by plotting the declination values on a map, aiding in field adjustments.

84. How can surveyors account for magnetic anomalies in an area to ensure accurate compass readings?

    • Answer: Surveyors can identify anomalies by comparing compass readings from different stations. Corrections or relocations may be necessary to mitigate the effects of magnetic anomalies.

85. Explain the concept of reciprocal bearings in compass surveying.

    • Answer: Reciprocal bearings are the opposite directions of a survey line, measured in both the forward and backward directions. The average of these readings helps eliminate errors.

86. What is the role of a transit lock on a compass, and when should it be used?

    • Answer: A transit lock stabilizes the compass needle during transit to prevent unnecessary movement. It should be engaged when the compass is not in use to prolong the life of the needle.

87. Describe the procedure for measuring the magnetic inclination using a dip circle.

    • Answer: Place the dip circle in the magnetic meridian, then tilt it until the needle is horizontal. The angle between the needle and the horizontal plane gives the magnetic inclination.

88. How can a compass surveyor determine the convergence angle at a specific location, and why is it important?

    • Answer: The convergence angle is calculated by subtracting the grid bearing from the true bearing or vice versa. It is crucial for accurate navigation and mapping in regions with significant convergence.

89. Explain the term “loop closure” in the context of compass traversing.

    • Answer: Loop closure refers to the precision of a traverse, where the final station should coincide with the starting station. Deviations indicate errors that need to be addressed for an accurate survey.

90. What measures can be taken to ensure the stability of a compass traverse in adverse weather conditions?

    • Answer: In adverse weather, secure the compass against wind and precipitation, use protective covers, and ensure a stable setup to maintain accuracy during measurements.

91. How does the choice of survey stations impact the accuracy of compass traversing, and what factors should be considered in station selection?

    • Answer: Survey stations should be strategically placed to ensure good visibility, minimize magnetic interference, and provide a clear line of sight between consecutive stations to enhance the accuracy of compass traversing.

92. Explain the process of correcting for magnetic dip when measuring vertical angles using a compass.

    • Answer: When measuring vertical angles, the observer should tilt the compass until the needle is horizontal and then correct the observed angle by subtracting the magnetic dip angle.

93. What is the significance of a declination correction sheet in compass surveying, and how is it utilized in the field?

    • Answer: A declination correction sheet provides information on magnetic declination at various locations. In the field, surveyors reference this sheet to correct compass readings by adding or subtracting the relevant declination.

94. Describe the role of a prism and peep sight in a prismatic compass and how they contribute to accurate readings.

    • Answer: The prism allows the surveyor to simultaneously view the compass card and the target, ensuring accurate readings. The peep sight aids in aligning the compass precisely with the target.

95. How does the size and type of needle impact the precision of a compass, and what considerations should be taken into account when choosing a compass needle?

    • Answer: A longer and more responsive needle enhances precision. The choice of needle material and its magnetic properties should be considered to minimize friction and achieve accurate readings.

96. Explain the term “angular misclosure” in compass traversing, and how is it computed?

    • Answer: Angular misclosure is the difference between the sum of interior angles and the product of (n-2) times 180°, where ‘n’ is the number of sides in a traverse. It indicates the angular error in the survey.

97. What is the role of an auxiliary compass in compass surveying, and when is it employed in the field?

    • Answer: An auxiliary compass is used to measure bearings when the main compass is not practical or feasible. It ensures additional measurements for cross-verification and increased accuracy.

98. How do magnetic anomalies in the Earth’s crust affect compass surveying, and what measures can be taken to minimize their impact?

    • Answer: Magnetic anomalies can cause local attraction, affecting compass readings. To minimize impact, surveyors should recognize anomalies, compare readings from different stations, and apply necessary corrections.

99. Describe the procedure for calculating the departure and latitude of a survey line using a compass traverse.

    • Answer: Departure and latitude are calculated using trigonometry. Departure is the product of the length and the cosine of the angle, while latitude is the product of the length and the sine of the angle.

100. What is the role of a declination control line in compass surveying, and how is it established in the field?

     • Answer: A declination control line is a reference line along which declination is constant. It is established by measuring the magnetic bearing of the line and applying corrections to account for declination changes.

101. Explain the concept of a “back azimuth” in compass surveying, and why is it valuable in fieldwork?

     • Answer: A back azimuth is the opposite direction of the observed azimuth. It is valuable for retracing a route, as adding 180° to the azimuth provides the opposite direction.

102. How does magnetic declination vary over time, and what measures can be taken to account for these variations in compass surveying?

     • Answer: Magnetic declination changes over time due to the movement of the Earth’s magnetic poles. Surveyors should use up-to-date declination values or adjust for changes when comparing with older maps or surveys.

103. Describe the procedure for measuring the magnetic intensity of a location using a magnetometer in compass surveying.

     • Answer: Place the magnetometer on a stable surface, ensure it is level, and record the magnetic intensity reading. Repeat the process at different locations for a comprehensive survey.

104. What are the advantages of using a solar compass in surveying, and in what situations is it preferable over a magnetic compass?

     • Answer: A solar compass uses the Sun’s position for orientation, eliminating the need for magnetic bearings. It is advantageous in areas with significant magnetic interference or when high precision is required.

105. Explain the term “compass needle lag” and its impact on compass readings during field surveys.

     • Answer: Compass needle lag refers to the delay in the movement of the needle when the compass is rotated. Surveyors should allow the needle to settle before recording readings to minimize errors.

106. How does the altitude of a location affect the atmospheric pressure, and why is this consideration important in compass surveying?

     • Answer: Atmospheric pressure decreases with increasing altitude. In compass surveying, corrections may be needed for changes in pressure to ensure accurate readings.

107. Describe the steps involved in the adjustment of a prismatic compass, and why is adjustment necessary in surveying?

     • Answer: Adjustment involves correcting errors in a compass, such as collimation error and scale error. It is necessary to ensure the instrument provides accurate and reliable measurements in the field.

108. What is the purpose of a “hinged needle” in compass surveying, and how does it contribute to ease of use in the field?

     • Answer: A hinged needle allows the compass needle to be lifted when not in use, preventing damage and reducing wear. It enhances the longevity and usability of the compass.

109. How can a surveyor use a compass to establish a baseline for further surveying work, and what considerations should be taken into account in baseline establishment?

     • Answer: A compass is used to measure the magnetic bearing of the baseline. Considerations include selecting a straight line, minimizing obstacles, and ensuring good visibility between stations.

110. Explain the purpose of a declination adjustment screw in a compass, and how is it used during field surveys?

     • Answer: The declination adjustment screw allows surveyors to set or adjust the declination on a compass. It is used to ensure that readings reflect true north or grid north as needed for accurate surveys.