GISP - Geographic Information Systems Professional Geospatial Data Manipulation Questions and Answers — Questions and Answers
Question 1: An environmental analyst needs to identify areas that are both within a protected wildlife habitat (polygon layer A) and designated as a floodplain (polygon layer B). The final output must contain the attributes from both input layers only for the areas where they overlap. Which geoprocessing tool is most appropriate for this task?
- Union
- Intersect (Correct answer)
- Erase
- Dissolve
Correct answer: Intersect
The Intersect tool computes a geometric intersection of the input features. Features or portions of features which overlap in all layers will be written to the output feature class, and the output will contain the attributes from all the input layers. This is equivalent to a spatial 'AND' operation, which is what the scenario requires.
Question 2: A GIS technician is changing the spatial resolution of a categorical raster dataset representing land cover types (e.g., forest, water, urban). To ensure that the output cell values are not altered through averaging and remain one of the original land cover codes, which resampling method should be used?
- Bilinear Interpolation
- Cubic Convolution
- Nearest Neighbor (Correct answer)
- Majority Filter
Correct answer: Nearest Neighbor
Nearest Neighbor resampling is the appropriate method for categorical (discrete) data because it assigns the value of the closest input cell to the output cell without creating new data values. Methods like Bilinear Interpolation and Cubic Convolution average the values of surrounding cells, which would create new, invalid values for a land cover classification. A Majority Filter is a focal tool, not a resampling method for changing resolution.
Question 3: A city planner is combining street centerline data from three adjacent municipalities into a single, comprehensive street network file for regional analysis. Each municipality's data is in a separate feature class. Which geoprocessing tool is designed to combine these datasets into one new feature class without modifying the original geometries or resolving boundaries?
- Dissolve
- Union
- Clip
- Merge (Correct answer)
Correct answer: Merge
The Merge tool is used to combine multiple input datasets of the same data type into a single, new output dataset. It does not alter the geometry of the input features but simply appends them together, making it ideal for combining adjacent datasets like the street files in this scenario.
Question 4: A city ordinance requires that all new liquor stores must be located more than 500 feet away from any school property. A planner needs to create a GIS layer that shows all areas within the city that are ineligible for a new liquor store based on this rule. Which geoprocessing tool should be used first on the school properties layer?
- Buffer (Correct answer)
- Near
- Thiessen Polygons
- Clip
Correct answer: Buffer
The Buffer tool creates polygons at a specified distance around input features. By creating a 500-foot buffer around all school properties, the planner can directly identify the exclusion zones mandated by the ordinance. The other tools serve different proximity or overlay functions not suited for this specific task.
Question 5: In raster analysis, which type of Map Algebra operation computes a new value for each cell based solely on the value of that same cell in one or more input rasters?
- Focal Operation
- Zonal Operation
- Global Operation
- Local Operation (Correct answer)
Correct answer: Local Operation
Local operations in Map Algebra are performed on a cell-by-cell basis. The output value for each cell location is a function of the input value at that same location from one or more raster layers. In contrast, focal operations use a neighborhood of cells, and zonal operations use defined regions.
Question 6: An analyst is cleaning a street centerline file and discovers that many road segments that should connect at intersections have small gaps between their endpoints. This type of topological error, where a line falls short of connecting to another line, is known as a(n):
- Overshoot
- Silver Polygon
- Undershoot or Dangle (Correct answer)
- Pseudonode
Correct answer: Undershoot or Dangle
An undershoot, also commonly referred to as a dangle or dangling node, is a topological error where a line segment fails to connect to the line segment it should intersect, leaving a gap. An overshoot occurs when a line extends beyond the feature it should connect to.
GISP - Geographic Information Systems Professional Geospatial Data Manipulation Questions and Answers
An environmental analyst needs to identify areas that are both within a protected wildlife habitat (polygon layer A) and designated as a floodplain (polygon layer B).
The final output must contain the attributes from both input layers only for the areas where they overlap.
Which geoprocessing tool is most appropriate for this task?