Geographic Information Systems Flashcards

What is the primary purpose of using a wetland buffer analysis in GIS for a Corps of Engineers Section 404 project?

Answer: To identify upland areas within a specified distance of wetland boundaries that may require additional review

Buffer analysis around wetland boundaries identifies adjacent upland areas that may be subject to regulatory consideration or secondary impact assessment under Section 404.

Google Earth Pro's historical imagery tool is useful in wetland delineation because it allows delineators to:

Answer: Review site conditions across multiple years to assess hydrological patterns and vegetation changes

Historical imagery in Google Earth Pro lets delineators observe seasonal and interannual variation in inundation, plant cover, and land use that supports hydrology and vegetation assessments.

In the context of GIS-based wetland mapping, what does 'positional accuracy' refer to?

Answer: How closely mapped feature locations match their true positions on the ground

Positional accuracy describes how closely the x,y coordinates of mapped features correspond to their actual real-world locations, which is critical for regulatory boundary delineations.

A wetland delineator wants to estimate the inundation extent for a 2-year storm event using a DEM. Which approach is most appropriate?

Answer: Using terrain analysis to identify areas below a calculated flood stage elevation

Terrain-based inundation modeling identifies all DEM cells below a specified flood stage, producing an estimated inundation extent for a given storm event.

Which of the following best describes the difference between a Digital Elevation Model (DEM) and a Digital Surface Model (DSM)?

Answer: A DEM represents bare-earth terrain while a DSM includes the heights of vegetation and structures

A DEM represents the bare-earth surface after removing vegetation and buildings, while a DSM captures the top of all surfaces including tree canopy and rooftops.

When digitizing a wetland boundary in GIS from field data collected with a GPS, what is 'snapping' used for?

Answer: Ensuring vertices and edges of adjacent features connect precisely without gaps or overshoots

Snapping forces newly digitized vertices to connect exactly to existing features, eliminating gaps and slivers that would otherwise create topological errors in the wetland boundary layer.

Which federal mapping program provides freely available, nationwide LiDAR-derived elevation data useful for wetland delineation support?

Answer: 3D Elevation Program (3DEP) managed by USGS

The USGS 3D Elevation Program (3DEP) provides high-resolution LiDAR-derived DEMs covering the contiguous U.S. that are widely used to identify subtle topography relevant to wetland delineation.