LSIT Geodesy and Control Surveys 2 — Questions and Answers
Question 1: The State Plane Coordinate System (SPCS) uses which map projections?
- Mercator and Azimuthal Equidistant
- Lambert Conformal Conic and Transverse Mercator (Correct answer)
- Albers Equal-Area and Orthographic
- Gnomonic and Stereographic
Correct answer: Lambert Conformal Conic and Transverse Mercator
SPCS uses Lambert Conformal Conic for states with greater east-west extent and Transverse Mercator for states with greater north-south extent.
Question 2: In the Universal Transverse Mercator (UTM) system, each zone spans how many degrees of longitude?
- 3°
- 9°
- 6° (Correct answer)
- 12°
Correct answer: 6°
The UTM system divides the world into 60 zones, each spanning 6° of longitude, for a total coverage of 360°.
Question 3: The combined scale factor (CSF) in grid surveying accounts for:
- The angular difference between grid north and geodetic north
- The conversion factor between NAD27 and NAD83 coordinates
- The deflection of the vertical at a survey station
- The ratio of grid distance to ground distance at a given location (Correct answer)
Correct answer: The ratio of grid distance to ground distance at a given location
The CSF converts ground distances to grid distances (or vice versa) by combining the map projection scale factor and the elevation factor.
Question 4: Meridian convergence (mapping angle γ) is defined as:
- The correction applied to reduce slope distance to horizontal distance
- The angular difference between grid north and geodetic north (Correct answer)
- The difference between ellipsoidal and geoidal heights at a point
- The scale factor variation along the central meridian
Correct answer: The angular difference between grid north and geodetic north
Meridian convergence is the angle between grid north and geodetic (true) north at a given point in a projected coordinate system.
Question 5: Continuously Operating Reference Stations (CORS) primarily support:
- Spirit leveling campaigns for vertical datum maintenance
- Tidal gauge monitoring for sea level change analysis
- Real-time weather forecasting for field survey planning
- High-accuracy GPS/GNSS positioning through continuous reference data (Correct answer)
Correct answer: High-accuracy GPS/GNSS positioning through continuous reference data
CORS stations provide continuous GPS/GNSS tracking data that surveyors access to perform high-accuracy positioning and control surveys.
Question 6: The combined scale factor for converting ground distances to grid distances is computed as:
- Meridian convergence multiplied by the projection distortion factor
- The grid scale factor divided by the elevation factor
- The elevation factor multiplied by the grid (projection) scale factor (Correct answer)
- Orthometric height divided by ellipsoidal height
Correct answer: The elevation factor multiplied by the grid (projection) scale factor
CSF = (elevation factor) × (grid scale factor), where the elevation factor accounts for height above the ellipsoid and the grid scale factor comes from the map projection.
Question 7: In the UTM system, what is the scale factor at the central meridian of each zone?
- 1.000000
- 1.000400
- 0.998600
- 0.999600 (Correct answer)
Correct answer: 0.999600
The UTM system uses a scale factor of 0.9996 at the central meridian to limit the maximum scale distortion within each zone to ±0.04%.
LSIT Geodesy and Control Surveys 2
The State Plane Coordinate System (SPCS) uses which map projections?