AEC FROM THE GROUND UP: CAD and GIS Integration30 Jun, 2004 By: James L. Sipes
New tools help combine drawing and analysis.
Why can't we have the best of both worlds? Why can't we combine CAD's drawing and editing tools with the spatial analysis tools of GIS? That's a question many CAD and GIS users have asked over the years, and fortunately software developers have been listening. Today these developers offer a variety of digital tools intended to make the integration of CAD and GIS easier than ever.
CAD vs. GISAs any CAD or GIS user knows, there are significant differences between the two technologies. CAD systems place an emphasis on 2D graphics, sketching, and coordinate geometry tools, while GIS focuses on mapping, data management, and geoprocessing. CAD uses mathematical models to generate precise forms such as circles, arcs, and parallel lines. GIS systems were developed around an arc/node topology model effective for storing, calculating, and analyzing spatial data. The limitation with the arc/node model is that it doesn't allow the creation of more precise information.
Reasons to Integrate CAD and GISWhy should we integrate CAD and GIS? Integration can enhance the work many design and professionals currently do. Engineers, architects, and other CAD users can gain a better understanding of complex issues by using spatial data, and geographers and planners can increase the accuracy of GIS projects by incorporating CAD-based drawing and editing tools (figure 1 and 2). Many engineers are also looking to integrate GIS into their projects because many agencies now require it.
Figure 1. With integrated GIS and CAD systems, you can create GIS topology and add CAD details. For example, here GIS DEMs (digital elevation models), hillshades, and DRGs (digital raster graphics) were brought into AutoCAD Map, and then landscape districts were digitized.
Integrating CAD and GIS opens up new opportunities that didn't exist before. "Architects and engineers could utilize GIS to expand their work in areas such as facility management, security assessment, homeland security, urban analysis and revitalization, and asset management," says Bill Miller, design manager with ESRI. "Architects or planners involved in urban regeneration need to look at a 12- to 20-block area, and they need to look at a wide range of factors such as land use suitability, noise, security analysis, green roof analysis, and economics." This type of analysis requires a GIS topology with the precision of CAD (figure 3).
When an engineering firm designs a hydraulic system for a city, its responsibilities are typically finished once the project is constructed, but the city has to manage and operate the facility. Instead of just turning over the project to the client, an engineer could have an ongoing role in the management and analysis of the hydraulic facility. CH2MHill, one of the giants in the engineering world, is getting involved in facility management because it allows the company to stay involved in a project for the long term and enjoy much higher profits-35% as compared to about 5% for standard engineering work.
The simplest approach to integrating CAD and GIS is through file translation, which involves converting one file format to another. Guthrie's Cad2Shape, for example, converts AutoCAD DXF/DWG files to ArcView/ESRI shapefile format. Autodesk's GIS Data Transformer Extensions (dtX) are add-ons for AutoCAD Map and Land Development Desktop, and Blue Marble integrates CAD and GIS through CADWriter, an ArcView GIS extension.
Direct read is similar to file translation except that data is read and converted on the fly rather than saved in a new file format. A concern with any type of file translation is the potential loss of precision or accuracy. It's also difficult to ensure that you have the most up-to-date information. An alternative is to provide shared access to a database by using an API (application programming interface). ESRI's CAD Client extension to ArcSDE, for example, embeds an API into a program such as MicroStation or AutoCAD so users can access both CAD and GIS features.
A number of CAD and GIS programs have taken the idea of integrating the capabilities of the two technologies seriously. Here's a sampling.
Figure 2. To finish this image, contours and DRGs were exported to AutoCAD for terrain modeling and digitizing of project limits. The final rendering completed in 3DStudio.
AutodeskAutoCAD Map 3D, MapGuide, Envision
Autodesk's AutoCAD Map 3D, MapGuide, and Envision (www.autodesk.com) all include some type of GIS capability. Map 3D includes AutoCAD 2005 and all its 2D tools, as well as new tools for building, analyzing, visualizing, and rendering 3D data. You can read 3D data directly from LandXML, DEM, and ASCII files, or you can use traditional drawing tools to create a variety of 2D and 3D representations of surfaces, including contours, surface triangles, elevation and slope, surface face direction, watershed areas, and grid and slope arrows.
Map 3D features improvements to its powerful import/export capabilities, precision mapping, data analysis, and thematic mapping. It also includes new customization capabilities and FDO, which gives you the capability to store stores maps in a central, external geographical data store using a variety of different data formats, including Oracle Spatial.
Many AutoCAD Map 3D users also include MapGuide in their bag of digital tools. The two programs work together well-you create data in AutoCAD Map 3D and then publish that data on the Internet using MapGuide.
Autodesk Envision 8 (formerly known as Autodesk OnSite Desktop) is a design and mapping tool that was developed for civil engineers and landscape architects. It has tools for 3D graphics and animation, object queries, thematic mapping, and spatial analysis. Autodesk Envision 8 also supports Tablet PC technology and provides an easy-to-use markup tool for redlining digital drawings.
Figure 3. This is one frame of a 90-second animation that was built from existing GIS data. GPS was used for the final field mapping, all terrain modeling was done in AutoCAD, and then everything was exported to 3D Studio and rendered in Worldbuilder.
OSIS (Online Spatial Information Systems)
OSIS, developed by Idisis (www.idisis.com) and offered through Avatech Solutions (www.avatechsolutions.com) combines Autodesk Map, MapGuide, and ARCHIBUS/FM to create a system geared primarily for facility managers. It also uses Cold Fusion and Flash to display maps on the Internet and allow Web users to interactively query data from plans and databases. All CAD drawings are georeferenced, and this level of accuracy enables spatial analysis at a mapping level. For ARCHIBUS users, the OSIS Web-based approach offers a new way to manage facilities and infrastructure. It stores information in a central location so that, through your Web broswer, you always get a comprehensive and accurate picture of what's going on.
As its name suggests, Bentley's MicroStation GeoGraphics (www.bentley.com) helps transform MicroStation into a powerful geospatial environment. You can perform spatial analysis, create thematic maps, and store attributes for use with other datasets. Earlier this year, Bentley Systems introduced the AEC/GIS Interoperability Initiative, which uses APIs to integrate ESRI's ArcGIS and Bentley's MicroStation. GeoGraphics is also Open GIS-compliant and uses an open Oracle Spatial database storage system, so a number of third-party companies have developed add-ons that address specific issues.
MicroStation is designed specifically for engineers and is used by most of the DOTs (departments of transportation) around the country. In fact, most DOTs require that all transportation projects be submitted in MicroStation format. As a result, GeoGraphics is a great choice for engineers who need to incorporate spatial data into a design for a new highway, interchange, or streetscape.
CompassTrac from CompassCom (www.compasscom.com) is for users who need to view CAD and GIS data, but don't necessarily need to modify it. Basically, CompassTrac lets you view CAD files that are linked to a GIS database. It's ideal for a construction manager who needs to verify drawings on the job site, a firefighter who needs precise drawings that show the layout of a building or the streets in an urban setting, or a city worker who needs to find manholes that connect to a particular sewer line. You can't modify or add information to the drawings or maps, so it's not useful for data collection.
For GIS professionals looking to integrate CAD into their work, ArcGIS 9 from ESRI (www.esri.com) is just the ticket. ArcGIS 8 introduced several CAD editing tools, and ArcGIS 9 continues that trend by adding even more. According to Bill Miller, the focus of ArcGIS 9 is on providing geoprocessing functionality, annotation and labeling improvements, geodatabase enhancements, and 3D visualization.
To add CAD/GIS interoperability, ArcGIS 9.0 includes a framework for file conversion, a CAD translator, CAD-like editing tools, support for Tablet PCs, and the ability to read files formats from AutoCAD, MicroStation, ArchiCAD, and SketchUp. It also includes a bidirectional CAD-GIS translator that can move data from a CAD system to a GIS and back again. ArcGIS 9 has upgraded existing technologies to support CAD formats such as Autodesk DWG/DXF 2002 and Bentley DGN V8, and it continues to add other formats.
As part of a long-term commitment to building a true 3D GIS, ESRI has made some significant advances in how 3D objects are integrated into ArcGIS 9. ArcGIS 3D Analyst introduces the ability to build, import, and display 3D symbols and models with photo textures that are true 3D models, not just extrusions of 2D polygons. These 3D objects are stored in a geodatabase. You can then use ArcScene to render and query them.
The result is greater flexibility and a higher level of realism in the models. ArcGlobe provides the capability to interact with any type of geographic information as data layers on a 3D globe.
Instead of taking a traditional 2D drawing approach like most CAD programs, Graphisoft's ArchiCAD 8.1 (www.graphisoft.com) creates a central database of 3D model data as you draw individual elements that make up a structure. The benefit is that once you finish a drawing, you already have 3D data that can be used for other purposes, such as creating sections and elevations, building 3D visualizations, and generating construction details and quantity takeoffs. All of the information about a building is stored in a central database, so you need to make changes only once. All objects have attributes tied to them, so they have some degree of intelligence. For example, if you put a door into a wall, the system understands that a portion of the wall needs to be physically removed to accommodate the door.
The current release of ArchiCAD includes Boolean geometry, making it easier to model organic shapes. The company has made a real effort to improve external compatibility, especially by making it easier to exchange information with 2D CAD programs. Graphisoft is also working with ESRI to integrate ArchiCAD with ArcGIS.
Haestad Methods' GIS Connect (www.haestad.com) is an add-on program for AutoCAD that provides access to thedata management and geospatial analysis capabilities of ArcGIS from within AutoCAD. GISConnect is developed with ArcObjects. It adds a series of menus and toolbars to your normal AutoCAD interface so that you can view and edit GIS features such as point data, coverages, and shapefiles. You can use native AutoCAD commands to perform GIS tasks. Because GISConnect is a "live" connection, there is no file translation involved. It requires you to have licenses for both AutoCAD and ArcGIS.
Any*GIS from Hitachi Software Global Technology (www.hsgt.com) is an object-oriented framework that lets you integrate all formats and sources through a common Web interface. This approach makes it easy to access GIS and CAD via the Internet. It conforms to the Open GIS technical specifications and is built on a multitiered framework that supports multiple GIS data sources from companies such as Autodesk, ESRI, Intergraph, MapInfo, Oracle, and Smallworld.
You can customize Any*GIS to meet your organization's specific GIS and CAD needs. Because Any*GIS is Web-based, users can access data from any location, whether it be in your office, in a public meeting, or in the field during site reconnaissance.
Intergraph's GeoMedia 5.2 (www.intergraph.com) provides a full suite of tools for attribute and spatial query, spatial overlays, and thematic mapping. GeoMedia users will notice that v5.2 presents a much different look and feel than previous versions. Its simplified user interface is consistent between the map and layout windows, and the graphic icons and dialog boxes make it easier to find what you're looking for. The new layout window looks more like a CAD interface than it did before, but all of the geospatial tools are still there. GeoMedia supports open standards and provides direct access to all major GIS and CAD data formats.
With MapInfo's MapInfo Professional 7.5 (www.mapinfo.com), you can combine data from widely different sources, even with different formats and projections, in the same map window. This latest version includes CAD-like features such as data editing functions, the ability to rotate or offset map objects using precise units or snap to specific objects, and an enhanced line creation and line snap/extend tool that extends or snaps to an object. You can work with vector and raster data at the same time, drape files over 3D terrain, and use the new prism mapping feature to extrude portions of a flat map to highlight specific types of information. MapInfo's MapX Mobile Tool exports MapInfo Professional map windows to a Pocket PC device, and MapInfo Discovery Connectivity lets you post map workspaces to a server where they can be viewed by anyone on the Web.
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The Future of GIS and CADAt one point, limitations in digital technology were the biggest barrier to CAD and GIS integration, but that's no longer the case. "Today, the limitation has more to do with the hesitancy of users to change the way they work," says ESRI's Bill Miller. Changes are difficult in any situation, and most of us find it hard to master new technology. Many CAD users find the whole idea of thematic mapping and spatial data a little daunting, and many who tried to integrate GIS into their work have given up out of frustration. GIS users who are used to thinking in terms of points and nodes find CAD programs overwhelming because of the demand for detail and precision. Most users need a reason to change before they actually make the leap and learn how to integrate CAD and GIS.
Many GIS programs are continuing to add more CAD-like drawing and editing tools, but don't expect them to match the capabilities of a program such as AutoCAD anytime soon. A common trend among GIS vendors is the continued development of Open GIS-compliant products. Java and Active X architectures, for example, make it easier to cross-reference information because they don't differentiate between CAD and GIS data.
CAD vendors such as Autodesk and Bentley are making a strong play to get into the GIS markets, both to expand their markets and to meet the demands of their customers. Future versions of ArcGIS will include a placement editor, additional 3D analysis tools, 3D search capabilities, sketch tools, and electronic work surfaces.
"There used to be a huge gap between CAD and GIS," says Miller. "But now it's probably more of a collision zone than a gap." CAD programs are including thematic mapping and spatial analysis tools, and GIS programs are including design and editing tools, a trend Miller believes will continue.
James L. Sipes is the founding principal of Sand County Studios in Seattle, Washington.
About the Author: James L. Sipes
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