AUGIWorld Magazine September/October 2007

AutoCAD Map 3D Finding the 3D in Map 3D: Surface Visualization I was presenting the new Plan Production feature within Autodesk® Civil 3D software at a recent gathering of my local AutoCAD® user group, Richmond AutoCAD Manifest. During the presentation I was asked a rather fundamental, yet insightful, question about Civil 3D. The question was this: “Where’s the 3D part of Civil 3D?” Because Plan Production has to do with the creation of plan sheets, there wasn’t much talk about the 3D modeling components of Civil 3D. On the other hand, an interesting point was brought up. Over the last several years we have been immersed in a paradigm shift from 2D drafting to 3D modeling. AutoCAD 2007 brought us an endless array of 3D tools, and products such as AutoCAD Civil 3D have worn the 3D nameplate since their inception. On the other hand, sister products such as AutoCAD Map 3D are relative newcomers to the 3D spectrum. Answering the question for Civil 3D is simply a matter of demonstrating the Civil 3D road design, surface grading, or even pipe design. Still, the bigger question remains: What puts the 3D into AutoCAD Map 3D? Unlike Civil 3D where just about everything is modeled in 3D, discovering the 3D abilities of Map 3D takes a little more digging around. A lesser known 3D function hidden within Map 3D is its DEM surface rendering and analysis abilities. Quite simply, DEM surfaces can be analyzed by elevation, slope, or even slope direction. Moreover AutoCAD Map 3D also has the ability to generate contours from a DEM surface. tal Terrain Model. While the literal definitions of the two are the same, the differdiffer ence is in their fundamental construction elements. DTM surfaces are built with triangles (TIN - Triangulated Irregular Network) and tend to be a little more accurate than DEM surfaces. DEM surfaces are built using a grid similar to a piece of graph paper. While university websites can become invaluable data sources, they do not always have everything. Luckily there is a onestop-shop of sorts available for all USGS Quad Sheet DEM surfaces. A complete index of USGS DEM surfaces can be found by navigating to the GIS Data Depot (www.data.geocomm.com/dem). From there you will be able to both locate and download DEM data. If downloading data from the GIS Data Depot, you will likely need the STDS2DEM utility, which is made available as a free download on the site. Keep in mind that Map 3D only supports DEM surfaces. Consequently you will need to convert a DTM surface to a DEM for analysis in AutoCAD Map 3D. Luckily AutoCAD Civil 3D affords users the flexibility of exporting any Civil 3D surface as a DEM file. Simply right-click the surface name in Civil 3D, and select “Export to DEM.” The resulting DEM file can then be imported into AutoCAD Map 3D using the procedure outlined below. While both are only as accurate as their sources, the malleable structure of a DTM is often preferred over the rigidly structured DEM format. The DEM surface DEM stands for Digital Elevation Model, whose literal definition is an interpolated and continuous surface representing the ground. Another term which is often interchanged with DEM is DTM, or Digi- The primary source for DEM data in the United States is the United States Geological Survey (USGS), which distributes DEM surface models to correspond with the quad sheets the organization also distributes. Many sites across the Internet host DEM surfaces for public download. Universities that have a GIS program often host a fair amount of GIS data for public download, which can often be found on their websites. It is relatively easy to find DEM surfaces among the data available to the public. The MAPWSPACE command will load the Map Task Pane. Using the Map Task Pane you will be able to connect to and manage external data connections and stylizations. To connect to a DEM surface, follow these steps. Click the “Data” button from the “Display Manager Tab.” Select “Add Raster Image or Surface Connection” from the resulting “Data Connect” tab. While the connection name doesn’t directly affect the functionality of Map, it’s considered a good practice to name your connections something logical. Naming a surface after the originating quad sheet is always a good place to start. After browsing to your DEM file, click “Connect”, and then “Add to Map.” w w w. A U G I . c o m Connecting to a surface 16 http://www.data.geocomm.com/dem http://www.AUGI.com

Table of Contents Feed for the Digital Edition of AUGIWorld Magazine September/October 2007

Contents The CAD Manager Feature: A Good First Impression ADT and SketchUp Team for Presentations Accessing Values: Now or Later Finding the 3D in Map 3D: Surface Visualization Rocks & Rock Walls Autodesk University 2007 Preview The Missing Link On the Back Page

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