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GIS Analysis Quiz1

Surface Quiz for COCC GEOG 287

What is a surface? A continuous field of values that may vary over an infinite number of points
What are some Discrete Surfaces? *Dot Distribution *Proportional Symbols *Choropleth *Isarithmic
What are the methods for creating Raster Surfaces? Interpolation *Inverse Distance Weighted *Trend Surface *Spine *Kriging
What are the methods for creating Vector Surfaces? Triangulation *TIN
How does TIN work? Constructed by triangulating vertices which are connected in a series of edges to form a network of triangles.
What is Delaunay Criteria? No vertex lies within the interior of any of the circumcircles of the triangles in the network.
Drawbacks of TIN surfaces? * Less available * Tend to cost more to build and process
What is Interpolation? Estimating unknown values that fall between known values
What is Linear Interpolation? Common Slope, most basic interpolation, assumes a linear line
What is Inverse Distance Weighting (IDW)? Sample points closer to the cell have a greater influence on the cell's estimated value than sample points that are farther away
What are some traits of IDW? *Will not exceed or pass through points *A points influence on the kernel is weighted by the square of the distance from the kernel
What is Spline Interpolation? Spline interpolation method fits a flexible surface through the known value locations
What are some traits of Splining? *Through each sample point and may exceed the value range of the sample point set.
What is Trend Surface Interpolation? “Best-fit” based on mathematical equation, uses orders i.g. 1st order, 2nd order, 3rd order to determine best fit.
What is Kriging Interpolation? Is an advanced geostatistical procedure that generates an estimated surface from a scattered set of points with z-values based on statistical models that include autocorrelation.
Describe the elements of a Semivariogram? *Sill- The Y- peak where the data levels out * Range - The X value where the peak of the data is *Nugget Variance - The Y Intercept (where the value crosses the Y axis)
What are some problems with Interpolation? *Number of sample points can limit accuracy *Location of sample points may not represent population *Saddle points *Don't extrapolate
What is Dasymetric Mapping? Mapping depicts quantitative areal data using boundaries that divide the area into zones of relative homogeneity with the purpose of better portraying the underlying distribution. *GIS does not have this capability, yet
Created by: Sevcav