assign16 - Assignment 16. GWR 3D Mapping Sources: ESRI...

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1 Assignment 16. GWR 3D Mapping Sources: ESRI online course on 3D Analyst ; Kennedy, Data in Three Dimensions: A Guide to ArcGIS 3D Analyst (Thomson/Delmar Learning, 2004). I: Background for 3D & ArcScene § Surfaces & features: a map layer may contain surfaces or features. o Surfaces: model a phenomenon that varies continuously across an area (e.g., elevation, slope, aspect, rainfall). Surfaces are modeled with raster data (i.e. consisting of grids of identically sized cells, or pixels, each of which represents a unit of surface areas & stores a measured or estimated value for a particular unit). § A surface can be estimated from sampled data via interpolation (see Spatial Analyst and Geostatistical Analyst: e.g., IDW, spline, nearest neighbor, kriging; see ArcGIS help). o Features: entities with discrete boundaries (e.g., houses, districts); features are represented vector data (i.e. by a polygon, line, or point). § Features are represented by 2D or 3D feature classes (i.e. sets of like features) such as shapefiles and geodatabases. § 3D feature: a point, line, or polygon with not only x,y coordinates also z-values as parts of its geometry. A z-value stores a measurement such as a base height. A point stores has one z-value, while lines & polygons have a single z-value for each vertex in the shape. How to identify shapefiles & geodatabase feature classes that store 3D features: the ‘shape’ field in the attribute table contains z-values that end with ‘ZM’ (e.g., PointZM). A TIN (i.e. Triangulated Irregular Network) represents space via a set of non-overlapping triangles that border each other & vary in size & proportion. o A TIN is created from a set of input points with x, y, & z values; the points become triangle vertices (nodes) that are connected by lines that form boundaries (edges)—a final product that is a continuous surface of triangles made of nodes & edges. o Slope & aspect can be calculated for each triangle face. 3D features are manipulated in ArcMap via ArcScene , which you need to load ( View menu>3D view tools). II: 3D in ArcCatalog Note: see Part VI, “Trouble shooting” § How to preview 3D features in ArcCatalog: o Note the symbols that represent a TIN & a raster. o Right-click practice.shp>Preview>Geography.
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2 § practice.shp displays in 2D. § How to find out if it can display in 3D? o Preview>Table. § practice.shp’s shape field says ‘ZM’, which means that it stores ‘measured values’ such as 3D. § If it couldn’t store measured values, the shape field would say ‘Polyline’ only. o In the tree, click practice_tin. Click Preview to display practice_tin in 2D. o Next, click 3D View to see practice_tin in 3D. What enables it to display in 3D? o
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assign16 - Assignment 16. GWR 3D Mapping Sources: ESRI...

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