GIS - Geographic Information System Map Projections and Datums Questions and Answers

Question 1

A GIS analyst in North America overlays two vector datasets of a county boundary.
One dataset is referenced to the North American Datum of 1927 (NAD27) and the other is referenced to the North American Datum of 1983 (NAD83).
The analyst observes a consistent spatial offset of approximately 40 meters between the two layers.
What is the most appropriate step to resolve this discrepancy?

Accepted Answer

Perform a datum transformation on one of the datasets.

Answer

Change the map projection of one layer to match the other.

Answer

Adjust the linear units of one layer from feet to meters.

Answer

Recalculate the feature geometry using a different spheroid model.

Question 2

A demographer is creating a world map to visually compare the population density of different countries. To ensure that the graphical size of each country on the map is directly proportional to its actual land area, which type of map projection property is most critical?

Accepted Answer

Equal-area

Answer

Conformal

Answer

Azimuthal

Answer

Equidistant

Question 3

Which of the following statements most accurately describes the core difference between a Geographic Coordinate System (GCS) and a Projected Coordinate System (PCS)?

Accepted Answer

A GCS defines locations on a 3D, curved model of the Earth using angular units (latitude/longitude), while a PCS represents locations on a flat, 2D surface using linear units (meters/feet).

Answer

A GCS uses linear units like meters and is best for analysis, while a PCS uses angular units like degrees and is best for data storage.

Answer

A GCS is based on the WGS 1984 datum by default, while a PCS must be based on a local datum like NAD27.

Answer

A GCS is inherently less accurate than a PCS because it does not account for the curvature of the Earth.

Question 4

An environmental agency is mapping a long, narrow river corridor that runs primarily north-to-south through a state. To minimize distortion for distance and shape measurements within this corridor, which map projection would be most suitable for their State Plane Coordinate System zone?

Accepted Answer

Transverse Mercator

Answer

Albers Equal Area Conic

Answer

Lambert Conformal Conic

Answer

Azimuthal Equidistant

Question 5

Which of the following best defines a horizontal datum?

Accepted Answer

A reference framework consisting of an ellipsoid, its orientation, and an origin point, which defines the size and shape of the Earth for mapping purposes.

Answer

A mathematical formula used to convert 3D coordinates to a 2D plane.

Answer

A collection of survey monuments that define a vertical elevation surface.

Answer

A system of grid lines, including a central meridian and standard parallels, used to establish x,y coordinates.

Question 6

A cartographer is creating a nautical chart where preserving the accuracy of local angles and shapes is the highest priority, ensuring that a straight line drawn on the map represents a line of constant bearing (a rhumb line). This type of projection, which prioritizes angle preservation, is known as:

Accepted Answer

Conformal

Answer

Equivalent

Answer

Equidistant

Answer

Gnomonic