CEP Geographic Information Systems 3 — Questions and Answers
Question 1: What is the main difference between a geographic coordinate system (GCS) and a projected coordinate system (PCS)?
- GCS uses meters while PCS uses degrees
- GCS uses latitude/longitude on a sphere while PCS uses x/y coordinates on a flat plane (Correct answer)
- GCS is more accurate than PCS for local areas
- GCS is used only for raster data while PCS is used for vector data
Correct answer: GCS uses latitude/longitude on a sphere while PCS uses x/y coordinates on a flat plane
A GCS references locations on a curved earth surface using degrees of latitude and longitude, while a PCS uses mathematical transformations to represent those locations on a flat, two-dimensional surface.
Question 2: An environmental planner uses GIS to merge two adjacent county-level datasets into a single seamless layer. Which operation achieves this?
- Intersect
- Clip
- Append (Correct answer)
- Erase
Correct answer: Append
The Append operation combines multiple datasets of the same feature type into one output dataset, making it ideal for merging adjacent geographic areas.
Question 3: Which interpolation method in GIS is considered an exact interpolator, meaning it honors all input data points exactly?
- Spline (Correct answer)
- IDW (Inverse Distance Weighted)
- Kriging
- Natural Neighbor
Correct answer: Spline
Spline interpolation is an exact interpolator that forces the surface to pass through all input data points while maintaining a smooth continuous surface.
Question 4: In GIS-based environmental impact assessment, what does a viewshed analysis determine?
- The visual quality of a landscape
- The area visible from one or more observer points based on terrain (Correct answer)
- The distance between habitat patches
- The flood inundation extent for a given storm event
Correct answer: The area visible from one or more observer points based on terrain
Viewshed analysis uses a digital elevation model to calculate which areas can be seen from specified observer points, critical for assessing visual impacts of proposed projects.
Question 5: What is the primary function of a spatial index in a GIS database?
- To assign unique identifiers to each feature
- To speed up spatial queries by organizing features by location (Correct answer)
- To ensure topology rules are enforced
- To convert coordinate systems automatically
Correct answer: To speed up spatial queries by organizing features by location
A spatial index organizes geographic features by their location, dramatically reducing query time when searching for features within a specific area.
Question 6: Which GIS concept describes the minimum distance between two distinguishable features on a map, related to map scale and display resolution?
- Positional accuracy
- Spatial resolution
- Map generalization
- Minimum mapping unit (Correct answer)
Correct answer: Minimum mapping unit
The minimum mapping unit (MMU) is the smallest feature that can be reliably represented at a given map scale, influencing decisions about what features to include in a dataset.
Question 7: An environmental planner wants to model how pollutants spread from a point source across a watershed. Which GIS capability is most relevant?
- Choropleth mapping
- Flow direction and accumulation analysis using DEM (Correct answer)
- Dasymetric mapping
- Cartographic generalization
Correct answer: Flow direction and accumulation analysis using DEM
Flow direction and accumulation analysis uses digital elevation models to trace the movement of water and associated pollutants across a landscape following terrain gradients.
CEP Geographic Information Systems 3
What is the main difference between a geographic coordinate system (GCS) and a projected coordinate system (PCS)?