PS Surveying Methods & Techniques 3 — Questions and Answers
Question 1: Which triangulation figure provides the strongest network geometry and is used in primary control surveys?
- Simple chain of triangles
- Quadrilateral without center point
- Braced quadrilateral (Correct answer)
- Open polygon
Correct answer: Braced quadrilateral
The braced quadrilateral (four sides and both diagonals) provides redundant angle observations and strong geometry, making it the preferred figure for primary triangulation networks.
Question 2: In GPS surveying, the term 'PDOP' refers to:
- Phase Difference of Oscillation Period
- Position Dilution of Precision (Correct answer)
- Pseudo-range Differential Observation Point
- Primary Data Output Protocol
Correct answer: Position Dilution of Precision
PDOP (Position Dilution of Precision) is a dimensionless factor that quantifies the effect of satellite geometry on the combined horizontal and vertical position accuracy.
Question 3: The figure-closure condition in a triangulation network requires that the sum of angles in each triangle equal:
- 360°00'00"
- 180°00'00" (Correct answer)
- 270°00'00"
- 90°00'00"
Correct answer: 180°00'00"
Each plane triangle in a triangulation network must satisfy the geometric condition that its three interior angles sum to exactly 180°00'00".
Question 4: When running a differential level circuit, the purpose of using equal backsight and foresight distances is to eliminate the effect of:
- Rod settlement and atmospheric refraction only
- Curvature of the earth and atmospheric refraction (Correct answer)
- Instrument centering error and parallax
- Temperature fluctuations on the rod
Correct answer: Curvature of the earth and atmospheric refraction
Balancing backsight and foresight distances cancels systematic errors due to earth curvature and atmospheric refraction, since both affect the readings equally.
Question 5: A surveyor sets up a total station and measures a horizontal angle of 47°32'18" to point A and 112°15'44" to point B. What is the angle between the two directions?
- 64°43'26" (Correct answer)
- 64°44'26"
- 159°48'02"
- 65°43'26"
Correct answer: 64°43'26"
The angle between A and B is 112°15'44" − 47°32'18" = 64°43'26".
Question 6: In plane-table surveying, the method where the instrument is set up at the unknown point and oriented by sighting known points is called:
- Radiation
- Traversing
- Intersection
- Resection (three-point problem) (Correct answer)
Correct answer: Resection (three-point problem)
The three-point problem (resection) on a plane table involves locating the table's position by drawing rays from three known points visible on the sheet without moving the table.
Question 7: During a GPS static survey, a minimum of how many satellites must be simultaneously observed to obtain a 3D position fix?
- 2
- 3
- 4 (Correct answer)
- 6
Correct answer: 4
A minimum of four satellites are required for a 3D GPS position fix: three satellites determine position in three spatial dimensions and a fourth resolves the receiver clock error.
PS Surveying Methods & Techniques 3
Which triangulation figure provides the strongest network geometry and is used in primary control surveys?