GIS - Geographic Information System Spatial Analysis Methods Questions and Answers — Questions and Answers
Question 1: A city planning department needs to identify all residential parcels that fall partially or wholly within 500 meters of a proposed new landfill site to send out notification letters. Which sequence of geoprocessing tools is most efficient for this task?
- Create a Union of the landfill and parcels layers, then Buffer the result.
- Erase the parcels layer with the landfill site, then Buffer the remaining parcels.
- Buffer the landfill site by 500 meters, then Intersect the buffer with the parcels layer. (Correct answer)
- Calculate the Near distance from all parcels to the landfill site.
Correct answer: Buffer the landfill site by 500 meters, then Intersect the buffer with the parcels layer.
The most direct method is to first create the area of interest by buffering the landfill site by 500 meters. Then, an Intersect operation with the residential parcels layer will create an output feature class containing only those parcels (or portions of parcels) that fall within the buffer zone. The attribute table of the output will contain information from both layers, making it easy to identify the property owners.
Question 2: An analyst is studying the spatial distribution of crime incidents in a city to identify statistically significant clusters of high-value areas (hot spots) and low-value areas (cold spots). Which spatial statistics tool is specifically designed for this purpose?
- Getis-Ord Gi* (Hot Spot Analysis) (Correct answer)
- Inverse Distance Weighting (IDW)
- Global Moran's I
- Kernel Density Estimation
Correct answer: Getis-Ord Gi* (Hot Spot Analysis)
The Getis-Ord Gi* statistic (Hot Spot Analysis) is used to identify statistically significant spatial clusters of high values (hot spots) and low values (cold spots). It evaluates each feature within the context of its neighboring features to determine if the local sum for a feature and its neighbors is proportionally larger or smaller than the global sum. While Kernel Density creates a density surface and Moran's I measures overall clustering, Getis-Ord Gi* is the specific tool for locating significant hot and cold spots.
Question 3: A conservation group wants to identify the most suitable areas for reintroducing a species of bear. Their criteria include: areas must be within a national forest, more than 2 kilometers from any major road, and on slopes less than 20 degrees. The analysis will use a land cover raster, a roads vector layer, and a digital elevation model (DEM). What is the most appropriate overall methodology for this analysis?
- Network Analysis
- Proximity Analysis using only Buffers
- Geocoding and Address Matching
- Weighted Overlay / Suitability Modeling (Correct answer)
Correct answer: Weighted Overlay / Suitability Modeling
Weighted Overlay, a form of suitability modeling, is the ideal method for this multi-criteria problem. It allows the analyst to combine multiple raster layers representing different criteria (e.g., land cover, distance from roads, slope), reclassify them to a common scale (e.g., 1-10), and assign weights to each criterion based on its importance to find the most suitable locations.
Question 4: Which of the following overlay operations combines the geometry and attributes of two input vector layers, but only for the areas where the two layers geometrically overlap?
- Union
- Intersect (Correct answer)
- Identity
- Erase
Correct answer: Intersect
The Intersect tool calculates the geometric intersection of input features. Features or portions of features which overlap in all layers will be written to the output feature class, along with the attributes from all input features. Union keeps all features from both layers, while Identity keeps all features from the primary input layer plus the overlapping parts of the second layer.
Question 5: A scientist has collected soil moisture readings from a set of discrete sample points scattered across a study area. To create a continuous surface map that predicts soil moisture values for all locations in the area, which type of spatial analysis should be performed?
- Spatial Interpolation (Correct answer)
- Spatial Autocorrelation
- Buffering
- Network Analysis
Correct answer: Spatial Interpolation
Spatial interpolation is the process of using points with known values to estimate values at other, unknown points to create a continuous surface. Common methods include Inverse Distance Weighting (IDW) and Kriging. This is the correct technique for converting discrete point measurements into a continuous raster surface representing the phenomenon.
Question 6: An emergency response agency wants to determine which parts of a city can be reached by an ambulance from a specific hospital within a 5-minute drive time, considering the road network and typical traffic speeds. Which type of spatial analysis is most suitable for this task?
- Viewshed Analysis
- Kernel Density Estimation
- Service Area Analysis (Correct answer)
- Weighted Overlay
Correct answer: Service Area Analysis
Service Area Analysis, a function of network analysis, is specifically designed to solve this problem. It creates a polygon (a service area) that encompasses all accessible streets within a specified travel time or distance along a network dataset. This is ideal for modeling emergency response times or retail catchment areas.
GIS - Geographic Information System Spatial Analysis Methods Questions and Answers
A city planning department needs to identify all residential parcels that fall partially or wholly within 500 meters of a proposed new landfill site to send out notification letters.
Which sequence of geoprocessing tools is most efficient for this task?