SAF Geographic Information Systems 3 — Questions and Answers
Question 1: A forest manager wants to combine a soils layer and a slope layer to identify areas suitable for timber harvest. Which GIS overlay operation produces a single output layer with attributes from both inputs?
- Clip
- Intersect (Correct answer)
- Erase
- Symmetrical Difference
Correct answer: Intersect
The Intersect operation returns the geometric intersection of two or more layers, retaining attributes from all input layers.
Question 2: What is the purpose of a Digital Elevation Model (DEM) in forest GIS applications?
- To store tree species classification data
- To represent bare-earth surface elevations for terrain analysis (Correct answer)
- To record canopy reflectance values from satellite imagery
- To manage tabular inventory data linked to stands
Correct answer: To represent bare-earth surface elevations for terrain analysis
A DEM represents bare-earth surface elevations and is used to derive slope, aspect, and watershed boundaries for forest planning.
Question 3: When classifying a satellite image into forest cover types, which supervised classification approach requires the analyst to define training samples first?
- ISODATA clustering
- K-means clustering
- Maximum Likelihood Classification (Correct answer)
- Principal Component Analysis
Correct answer: Maximum Likelihood Classification
Maximum Likelihood Classification is a supervised method requiring analyst-defined training samples to represent each cover class.
Question 4: Which coordinate system uses easting and northing values in meters and divides the world into 60 numbered zones, commonly used in US forestry GPS work?
- State Plane Coordinate System
- Geographic Coordinate System
- Universal Transverse Mercator (UTM) (Correct answer)
- Lambert Conformal Conic
Correct answer: Universal Transverse Mercator (UTM)
UTM divides the world into 60 zones, using metric easting/northing values and is widely adopted for GPS-based field data collection in forestry.
Question 5: In raster GIS analysis, what does 'cell resolution' determine?
- The number of attribute fields stored per cell
- The geographic area represented by each pixel (Correct answer)
- The color depth of the raster display
- The maximum number of raster layers in a project
Correct answer: The geographic area represented by each pixel
Cell resolution defines the ground area represented by each pixel; a 30m resolution means each cell covers a 30×30 meter area.
Question 6: A forester uses GIS to delineate watersheds for a riparian buffer study. Which DEM derivative is most critical for this analysis?
- Hillshade
- Flow direction and flow accumulation grids (Correct answer)
- Slope in degrees
- Aspect raster
Correct answer: Flow direction and flow accumulation grids
Flow direction and flow accumulation grids derived from a DEM are the foundation for watershed delineation and drainage network mapping.
Question 7: What is the primary function of metadata in a GIS forest data layer?
- To store the actual spatial geometry of features
- To document data source, accuracy, projection, and creation date (Correct answer)
- To compress the file size for faster processing
- To define symbology for map display
Correct answer: To document data source, accuracy, projection, and creation date
Metadata documents the who, what, when, where, and how of a dataset, enabling users to evaluate data quality and fitness for use.
SAF Geographic Information Systems 3
A forest manager wants to combine a soils layer and a slope layer to identify areas suitable for timber harvest.
Which GIS overlay operation produces a single output layer with attributes from both inputs?