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23 Cards in this Set
- Front
- Back
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Surfaces |
Model friction or impedance Grouped in slopes and aspects, viewsheds-valleys, hills, watersheds Continuous -elevation, temperature Discrete= population density |
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What are Surfaces |
Features containing height values (Z) distributed throughout areas defined by sets of X, Y coordinates |
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Surface Creation |
Sampling at critical locations, use interpolation to fill gaps. Statistical - dot mapping, chorpleth, dasymetric, isarithmic |
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Sampling Statistical Surfaces |
Isometric map=isolines, known Z values sampled at point locations Isoplethics=Isolines, Z values recorded for polygonal areas, can create centroids Selection of data- regular lattice or irregular lattice |
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Data Models for Statistical Surfaces |
TIN- Vector data DEM-discrete altitude matrix-point image method, each contain single elevation value Raster Surface=each unit can contain only single absolute elevation value. Converts continuous data to discrete |
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Interpolation Methods |
Calculate slopes, aspects, cross sections and predict elevations for objects, do not have data for. Linear/Nonlinear - can involve assumption Saddle point problem |
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Four characteristics of three dimensional surfaces |
Steepness of slope Azimuth-orientation shape/form intervisibility |
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Steepness of slope |
rise over run, change in elevation over horizontal distance |
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Azimuth |
Surfaces exhibit slopes, oriented in particular direction |
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Shape/Form |
Classify statistical surfaces to provide measure of form. Cross sectional profile simplest method. |
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Intervisibility |
Line of sight, viewshed |
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Spatial Arrangements |
Placement, ordering, concentration, connected-ness, or dispersion of objects within confined geographic area |
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Point Patterns |
Most common technique Simplest measure= divide # of points by total area Patterns- uniform -pattern in area same as pattern in another area Regular-separated by same distance Random- scattered Clustered= tight |
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=Quadrant Analysis |
Uniform point patterns defined by relationships among uniform quadrants.
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Chi-squared test- |
Xsquared =SUM((O-E)Squared/E) O=observed E=Expected Chi value- low-pattern is uniform
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Overlay Analysis |
Graphic and Attribute analysis Cartographic overlay
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Types of Overlay Analysis |
Point-in Polygon= results in point feature Point carries polygon attributes in addition to own |
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Types cont'd |
Line in Polygon results in line feature Contains Line attributes + polygon attributes |
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Types |
Polygon-result is polygon Carries attributes of both layers |
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Types of Overlay |
Exclusionary-And, Or, XOr Mathematcally- Assign weight to variables, use buffers, arithmetic calculations Selective= Rule Based= If, then else |
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Overlay in Vector |
CAD type= limited analytical power, output visual land requires manual interpretation Topological Vector= Great analytical power, output both visual & GIS dataset, Sliver polygon problems |
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Venn Diagrams |
And= Intersection Or= Union XOR= complement or exclude Resembles graphic overlay method in GIS |
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Raster Overlay |
Use Map Algebra, add values in cells |
