SAF Geographic Information Systems 2 — Questions and Answers
Question 1: Which map projection is most commonly used for large-scale forestry operations in the contiguous United States?
- Mercator
- Albers Equal-Area Conic (Correct answer)
- Stereographic
- Robinson
Correct answer: Albers Equal-Area Conic
Albers Equal-Area Conic preserves area relationships, making it ideal for measuring forest extent across the contiguous US.
Question 2: In a GIS forest inventory, what does a 'topology rule' primarily enforce?
- Color coding of species layers
- Spatial relationships between features such as no gaps or overlaps (Correct answer)
- Attribute table column naming conventions
- Raster resolution standards
Correct answer: Spatial relationships between features such as no gaps or overlaps
Topology rules enforce spatial integrity by ensuring features relate correctly, such as stand polygons having no gaps or overlaps.
Question 3: A forester needs to identify all stands within 300 meters of a perennial stream. Which GIS operation is most appropriate?
- Clip
- Dissolve
- Buffer (Correct answer)
- Union
Correct answer: Buffer
A buffer operation creates a zone of specified distance around a feature, in this case 300 m around stream lines.
Question 4: What is the primary advantage of using a geodatabase over a shapefile for managing a large forest inventory?
- Smaller file size per layer
- Support for topological rules, domains, and relationship classes (Correct answer)
- Faster rendering in web browsers
- Compatibility with more GPS devices
Correct answer: Support for topological rules, domains, and relationship classes
Geodatabases support topological rules, attribute domains, subtypes, and relationship classes that shapefiles cannot enforce.
Question 5: When performing a spatial join in a forestry GIS, what is the key distinction between 'one-to-one' and 'one-to-many' join types?
- One-to-one joins work only with raster data
- One-to-many retains all matching records while one-to-one keeps only the first match (Correct answer)
- One-to-one joins require identical projections
- One-to-many joins only work with point features
Correct answer: One-to-many retains all matching records while one-to-one keeps only the first match
A one-to-many join retains all matching records from the join layer, while a one-to-one join keeps only the first (or summarized) match per target feature.
Question 6: Which remote sensing index is most commonly used to detect forest stress and declining canopy health?
- NDWI (Normalized Difference Water Index)
- NDVI (Normalized Difference Vegetation Index) (Correct answer)
- SAVI (Soil-Adjusted Vegetation Index)
- EVI (Enhanced Vegetation Index)
Correct answer: NDVI (Normalized Difference Vegetation Index)
NDVI uses near-infrared and red bands to quantify vegetation greenness, making it the standard index for monitoring canopy health.
Question 7: In LiDAR-derived data used for forestry, what does 'point cloud density' (points per square meter) primarily affect?
- The geographic extent of coverage
- The accuracy of canopy height models and tree detection (Correct answer)
- The color accuracy of RGB imagery
- The datum used for vertical measurements
Correct answer: The accuracy of canopy height models and tree detection
Higher point cloud density allows finer resolution canopy height models and improves individual tree detection accuracy.
SAF Geographic Information Systems 2
Which map projection is most commonly used for large-scale forestry operations in the contiguous United States?