GIS Spatial Analysis Methods 3

Question 1

What is the main difference between a raster overlay and a vector overlay in GIS?

Accepted Answer

Raster overlays combine cell values mathematically while vector overlays create new geometric intersections

Answer

Raster overlay applies map algebra to combine pixel values, while vector overlay geometrically intersects features to create new polygons with combined attributes.

Question 2

In geostatistics, what is a 'nugget' in the context of a semivariogram?

Accepted Answer

The semivariance at zero distance, representing measurement error or micro-scale variation

Answer

The nugget is the y-intercept of a semivariogram model, representing variability at distances smaller than the sampling interval or measurement error.

Question 3

Which type of spatial analysis would best identify retail locations that are underserved by existing stores?

Accepted Answer

Service area analysis

Answer

Service area analysis delineates the geographic reach of existing stores, allowing identification of areas beyond current service coverage.

Question 4

What does a negative Moran's I value indicate about a spatial dataset?

Accepted Answer

Negative spatial autocorrelation (dispersion)

Answer

A negative Moran's I indicates negative spatial autocorrelation, where dissimilar values tend to be located near each other (checkerboard pattern).

Question 5

In the context of raster analysis, what is 'focal statistics'?

Accepted Answer

Statistics computed for each cell based on values within a defined neighborhood

Answer

Focal statistics calculate output values for each cell using a moving window or neighborhood of surrounding cells, such as focal mean or focal maximum.

GIS - Geographic Information System Practice Test

GIS - Geographic Information System Practice Test

GIS Spatial Analysis Methods 3