CF Technology & Digital Tools 3 — Questions and Answers
Question 1: Which spectral band is most useful for detecting vegetation stress caused by insect infestation or drought in multispectral imagery?
- Blue (450–490 nm)
- Red (630–690 nm)
- Near-infrared (NIR, 750–900 nm) (Correct answer)
- Mid-infrared (MIR, 1550–1750 nm)
Correct answer: Near-infrared (NIR, 750–900 nm)
Stressed vegetation reflects less NIR than healthy vegetation, making NIR the primary band for detecting canopy stress.
Question 2: In a forestry database, what is the purpose of a 'relational' structure compared to a flat file?
- It stores raster imagery alongside vector data
- It links multiple tables via common keys to reduce redundancy and improve query efficiency (Correct answer)
- It converts field measurements to geographic coordinates automatically
- It compresses data to minimize storage requirements
Correct answer: It links multiple tables via common keys to reduce redundancy and improve query efficiency
Relational databases use primary and foreign keys to link tables, avoiding data duplication and enabling complex queries across datasets.
Question 3: What does the acronym 'NDVI' stand for and what does it measure?
- Normalized Difference Vegetation Index — a ratio indicating vegetation greenness (Correct answer)
- Net Digital Volume Inventory — total merchantable volume in a stand
- National Data Verification Index — data quality score in national forest inventories
- Normalized Density of Visible Individuals — a wildlife survey metric
Correct answer: Normalized Difference Vegetation Index — a ratio indicating vegetation greenness
NDVI = (NIR − Red) / (NIR + Red) and provides a dimensionless index of vegetation photosynthetic activity and cover density.
Question 4: A forester needs to delineate watersheds automatically from elevation data. Which GIS function is most appropriate?
- Kriging interpolation
- Hydrological flow accumulation and watershed delineation tools (Correct answer)
- Supervised classification
- Buffer analysis
Correct answer: Hydrological flow accumulation and watershed delineation tools
Hydrological tools use DEM flow direction and accumulation grids to automatically delineate watershed boundaries and stream networks.
Question 5: Which data format is the native vector format of Esri ArcGIS and widely used in US forestry GIS workflows?
- GeoJSON
- Shapefile (.shp) (Correct answer)
- KML
- GeoPackage (.gpkg)
Correct answer: Shapefile (.shp)
The shapefile format, though legacy, remains dominant in US forestry GIS due to its long history with Esri products and widespread compatibility.
Question 6: When using drone (UAS) imagery for forest inventory, what is the primary limitation compared to manned aircraft or satellite imagery?
- Inability to capture multispectral data
- Limited coverage area per flight and FAA airspace regulations (Correct answer)
- Lower spatial resolution than commercial satellites
- Incompatibility with GIS software
Correct answer: Limited coverage area per flight and FAA airspace regulations
Drones cover small areas per battery charge and flight, and operators must comply with FAA Part 107 rules including airspace authorizations.
Question 7: What is the function of 'attribute data' in a GIS vector layer representing forest stands?
- It defines the spatial extent and shape of each polygon on the map
- It stores descriptive information (e.g., species, age, basal area) linked to each feature (Correct answer)
- It controls the color and symbology displayed on the map
- It stores elevation data for terrain analysis
Correct answer: It stores descriptive information (e.g., species, age, basal area) linked to each feature
Attribute data is the tabular information in a GIS feature's associated table, providing non-spatial descriptors linked to each geographic feature.
CF Technology & Digital Tools 3
Which spectral band is most useful for detecting vegetation stress caused by insect infestation or drought in multispectral imagery?