GIS For Engineering (Knowledge) 4 — Questions and Answers
Question 1: What is the key difference between a TIN (Triangulated Irregular Network) and a raster DEM in GIS engineering applications?
- A TIN stores color imagery while a DEM stores elevation
- A TIN uses irregularly spaced triangles that can preserve breaklines, while a DEM uses a regular grid of cells (Correct answer)
- A TIN is used only for 2D mapping while a DEM is 3D
- A TIN is always more accurate than a DEM
Correct answer: A TIN uses irregularly spaced triangles that can preserve breaklines, while a DEM uses a regular grid of cells
TINs adapt triangle density to terrain complexity and can honor breaklines like ridges and streams, making them well-suited for detailed engineering surface modeling.
Question 2: In GIS-based utility corridor planning, which analysis combines multiple weighted layers to identify the most suitable route?
- Raster overlay suitability analysis (Correct answer)
- Attribute table join
- Feature class merge
- Proximity heat map
Correct answer: Raster overlay suitability analysis
Weighted raster overlay assigns importance scores to criteria layers (slope, land use, wetlands) and combines them to produce a composite suitability surface for route selection.
Question 3: What is the purpose of a datum transformation in GIS engineering projects that merge datasets from different sources?
- To change the file format of geospatial data
- To mathematically convert coordinates from one geodetic datum to another (Correct answer)
- To simplify complex polygon boundaries
- To reclassify raster values into fewer categories
Correct answer: To mathematically convert coordinates from one geodetic datum to another
Datum transformations shift coordinates between reference ellipsoids (e.g., NAD27 to NAD83), which is critical when combining legacy survey data with modern GPS data.
Question 4: Which GIS operation would an engineer use to determine the area of land within 500 feet of a proposed road that has slopes greater than 15%?
- Intersect slope raster with a buffer zone (Correct answer)
- Perform a spatial join on attribute fields
- Run a kernel density estimation
- Apply a natural breaks classification
Correct answer: Intersect slope raster with a buffer zone
Intersecting a slope-derived raster (reclassified to show areas >15%) with a 500-foot road buffer identifies the land meeting both spatial criteria simultaneously.
Question 5: In GIS, what does LIDAR point cloud data offer that traditional photogrammetry cannot easily provide for engineering surveys?
- Color imagery for land classification
- Accurate ground elevation beneath vegetation canopy (Correct answer)
- Parcel boundary information
- Zoning code attribution
Correct answer: Accurate ground elevation beneath vegetation canopy
LiDAR pulses can penetrate gaps in vegetation canopy to return ground-level elevation points, enabling accurate bare-earth DEMs even in forested areas.
Question 6: What is the significance of the 'Z-factor' parameter when performing slope analysis in GIS on data where XY units and elevation units differ?
- It sets the color scale for slope visualization
- It converts elevation units to match the XY units to ensure accurate slope calculations (Correct answer)
- It defines the number of slope classes
- It controls the DEM resampling resolution
Correct answer: It converts elevation units to match the XY units to ensure accurate slope calculations
When XY coordinates are in degrees (geographic) but elevation is in meters, a Z-factor converts elevation to consistent units, preventing gross slope calculation errors.
Question 7: Which GIS data model is best suited for modeling an underground storm sewer network in an engineering GIS system?
- Continuous raster surface
- Geometric network or utility network dataset (Correct answer)
- Thiessen polygon layer
- Triangulated irregular network
Correct answer: Geometric network or utility network dataset
Geometric networks or utility network datasets model pipes, manholes, and their connectivity, supporting flow tracing and isolation analysis for storm sewer engineering.
GIS For Engineering (Knowledge) 4
What is the key difference between a TIN (Triangulated Irregular Network) and a raster DEM in GIS engineering applications?