FUNDAMENTAL SURVEYING Geodesy and Map Projections 2 — Questions and Answers
Question 1: What is the scale factor in State Plane Coordinates?
- The ratio of grid distance to ground distance (Correct answer)
- The ratio of map scale to true scale
- The difference between NAD83 and NAD27
- The combined scale and elevation factor
Correct answer: The ratio of grid distance to ground distance
The scale factor (k) is the ratio of grid distance to geodetic distance on the ellipsoid at a given location.
Question 2: What is the combined scale factor used for in surveying computations?
- To convert slope distances to horizontal
- To convert ground distances to grid distances (or vice versa) (Correct answer)
- To convert geodetic coordinates to geographic
- To apply atmospheric corrections to EDM
Correct answer: To convert ground distances to grid distances (or vice versa)
The combined scale factor (= ellipsoid factor × scale factor) converts ground distances to grid distances for use in SPC or UTM computations.
Question 3: UTM (Universal Transverse Mercator) divides the world into how many zones?
- 18 zones
- 36 zones
- 60 zones (Correct answer)
- 72 zones
Correct answer: 60 zones
UTM divides the world into 60 zones, each 6° of longitude wide, numbered 1–60 from west to east.
Question 4: What is the central meridian scale factor in the UTM projection?
- 1.0000
- 0.9996 (Correct answer)
- 1.0004
- 0.9960
Correct answer: 0.9996
UTM uses a scale factor of 0.9996 at the central meridian to reduce maximum distortion across the 6° zone.
Question 5: What is the 'convergence angle' (γ) in a map projection?
- The angle between true north and magnetic north
- The angle between grid north and true (geodetic) north (Correct answer)
- The angle of tilt of the ellipsoid axis
- The angle between two survey lines
Correct answer: The angle between grid north and true (geodetic) north
The convergence angle (grid declination) is the angular difference between grid north and true (geodetic) north at any given point.
Question 6: What does the 't-T' correction account for in geodetic surveying?
- Temperature effects on steel tape
- The difference between the geodetic azimuth of a line and its grid azimuth due to meridian convergence (Correct answer)
- The effect of tidal variation on heights
- The time delay in GPS signals
Correct answer: The difference between the geodetic azimuth of a line and its grid azimuth due to meridian convergence
The 't-T' correction (arc-to-chord correction) accounts for the fact that a geodesic on the ellipsoid projects as a curve on a plane grid.
FUNDAMENTAL SURVEYING Geodesy and Map Projections 2
What is the scale factor in State Plane Coordinates?