GEOGRAPHIC INFORMATION SYSTEMS Lecture 25: 3D Analyst

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1 GEOGRAPHIC INFORMATION SYSTEMS Lecture 25: 3D Analyst 3D Analyst - 3D Analyst is an ArcGIS extension designed to work with TIN data (triangulated irregular network) - many of the tools in 3D Analyst also work with raster data (with some duplicated from Spatial Analyst) - used to create 3D models of terrain and 3D features (x, y and z values) TIN Data Structure - TINs are a type of vector data format - TINs are composed of contiguous, nonoverlapping triangles - TIN components are nodes, edges and faces which form the triangles - the TIN data structure uses irregularly shaped triangular facets to model terrain - each triangle is defined by three nodes with elevation values (each node has an x,y and z value) - the three nodes are then connected by lines to form a triangle - using the x,y and z coordinates of the nodes, each triangular facet has a defined slope and aspect Example triangulated irregular network (TIN) generated from a digital elevation model TINs are created from rasters or mass points - 3D models of terrain - TINs can be created from a raster digital elevation model (DEM) - or TINs can be created from mass points (points that have a height or z value) - once a TIN is created, it can be used to create contour maps, slope maps and aspect maps - 3D features (x, y and z values) - 3D features (points, lines or polygons) are created from vector data - assigns a z value to features based upon a height or depth attribute - 3D features can then be overlaid on the terrain (either a DEM or TIN elevation model) 3D Analyst Tools - a few of the more important tools contained in the 3D Analyst toolbox include: - 3D features - used to create 3D features (points, lines or polygons) - Conversion - used to create a TIN from a raster (e.g. DEM) or raster from a TIN - Raster Interpolation - used to interpolate a raster surface from sample points or contours - Raster Surface - used to create contours, slope maps, aspect maps, hillshades, viewsheds - TIN Surface - used to create contours, slope maps and aspect maps from a TIN Copyright 2015, Kevin Mulligan, Texas Tech University

2 ArcScene - a separate application program that is included with 3D Analyst - ArcScene is designed for viewing 3D terrain models and 3D features - with ArcScene you can pan, zoom, tilt and rotate GIS layers - the Fly button on the ArcScene toolbar also allows you to fly through the terrain - to create a 3D terrain model, grid cells in a DEM or nodes in a TIN are assigned a base height - in this case, the base height layer is the same as the original DEM or TIN - to create a 3D image terrain model, the pixels in an image are assigned a base height - in this case, the base height is either a DEM or TIN with the same extent as the image - ArcScene can also be used to visualize 3D features overlaid on a terrain model - to do this, features are assigned a base height from either a raster or TIN elevation model - these features are then extruded from the base height based upon a z attribute value - ArcScene can also be used to create to create and save animations - you can create and save an animation of a fly-through - you can also create and save animations to visualize time-series data - these animations can then be saved as video files (e.g. mpg or avi files) ArcScene view of Redlands with extruded building footprints overlaid on 3D terrain ArcGlobe - a separate application program that is included with 3D Analyst - designed for viewing 2D and 3D features on a virtual globe - the layers displayed on the globe can be either a raster, vector or TIN layers - the layers displayed in the ArcGlobe environment maintain their attribute table - the layers can be symbolized, selected, queried or analyzed on the globe - note that this is something that cannot be done in Google Earth Copyright 2015, Kevin Mulligan, Texas Tech University

3 GIST 3300 / D Analyst TIN Data Structure 1) Triangulated Irregular Network 2) 3D Models of Terrain 3) 3D Features 3D Analyst Application Programs ArcScene fly-throughs and animations ArcGlobe virtual globe 3D Analyst Extension - extension to ArcGIS designed to work with TIN data (Triangulated Irregular Network) - 3D representation of data 1

4 3D Analyst Extension -1) TINs are a form of vector data composed of contiguous, nonoverlapping triangles - used to represent surface morphology - TIN components are nodes, edges and faces which form the triangles - We now have 3 types of data models: vector, raster and TIN for 3D representation. 3D Analyst Extension - Created by 1) converting from a raster or 2) by triangulating a set of points > > 2

5 3D Analyst Extension 2) 3D models of terrain - TINs can be created from a raster - TINs can be used to create contour maps, slope maps, aspect maps, shaded relief (hillshades) and viewsheds 3D Analyst Extension 2) 3D models of terrain - TINs can be created from mass points (that have height value) 3

6 3D Analyst Extension - Example 3D models of terrain (using TINs or raster) and 3D features 3D Analyst Extension 3) 3D features (x, y and z values) - 3D features (points, lines or polygons) are created from vector data - assign a z value to features based upon an elevation or attribute value - 3D features can then be overlaid on terrain 4

7 3D Analyst Extension to ArcGIS Some tools found in 3D Analyst are the same as those in Spatial Analyst Interpolation tools Reclass Surface Analysis Visibility Analysis - but there are also many new tools designed to work with TINs 3D Analyst Extension to ArcGIS ArcScene (separate application program included with 3D Analyst) Access from the Start menu - designed for viewing 3D terrain models and 3D features 1) used to create 3D fly-throughs of a terrain model - terrain model can be either a raster or a TIN 2) used to visualize 3D features overlaid on a terrain model - features are assigned a base height (elevation) - features are extruded based upon an attribute value 3) can also be used to create animations - animation of a fly-through - visualization of time-series data - these animations are saved as video files (e.g. mpg or avi files) 5

8 3D Analyst Extension to ArcGIS ArcGlobe (separate application program included with 3D Analyst) - designed for displaying 2D and 3D features on a globe - similar to Google Earth, but works with ArcMap data layers 6