GIS Tech News #1421 Feb, 2006 By: Kenneth Wong
Marriage of Inconvenience
Merging building and terrain models in rapid prototypes
In the physical world, your house is grounded to a specific place on earth (we hope, for your sake), identifiable by latitude and longitude. In the 3D universe, a house is usually anchored to a hypothetical reference point (with x,y,z values set to 0:0:0 by default). For positioning objects, geospatial applications use relative coordinates, as described in the former approach. Almost all architectural modeling programs use absolute coordinates, as described in the latter.
This fundamental difference--one of the many that exist between GIS and CAD--would be of little consequence to civil engineers and architects if they didn’t have any reason to share data. But they do. And now that the use of 3D data is becoming prevalent in both fields, the search for a way to reconcile incompatible GIS and CAD data has become a worthy quest for some.
Recently, Cadalyst columnist James Sipes, a geospatial Galahad in his own right, chronicled his search for this Holy Grail in “Spatial Technologies: Integrating CAD and GIS.” We’ll take a parallel journey into the realm of rapid prototyping, where the standoff between geospatial and architectural data persists.
In Minturn, buried deep in snowy Colorado, Charles Overy and his staff at Laser Graphic Manufacturing sculpt physical models to their clients’ specifications. Among those clients are land planners and developers. They usually want not just scale-model buildings but composite models that show how architectural structures fit into their designated sites and surroundings. To manufacture these, Overy usually has to consolidate four different types of data: the architectural CAD model, the civil data of the site, the land survey data of the site and the geospatial data of the surrounding area. Recent advances may have made digital tools easier to deploy and use in each discipline, but for someone like Overy who must combine the various data types, the process has actually become more complex.
Show Me the Metadata
“One of the issues,” explains Overy, “is the lack of good metadata tags, which gives us the architectural or land planning projections.” Some of the data supplied to Overy tends to be relative to a local coordinate system specific to the project site. Roger A. Kelesoglu, director of Business Development at Z Corporation, which develops 3D printers, clarifies that it’s because the engineering department might work in local coordinate systems and provide contours rather than mesh data to architects and service bureaus.
“At some point,” he says, “some senior person might have tagged the correct UTM zone or projection, but why that decision was made, who made it, how it was made and how it was recorded was rarely part of the data that we receive. We have to make endless phone calls to track that information down, because if we have that, we can use tools like Global Mapper, Visual Nature Studio or an Autodesk product to bring everything together.”
“The primary file format for rapid prototyping is STL or VRML,” explains Overy. “VRML can track some metadata, but STL doesn’t even have units. It doesn’t even give us what units the measurements are in--it gives us pure geometry.” He wishes technology providers and practitioners could get together to come up with a common standard for rapid prototyping and CNC (computer numerical control). “Something that contains metadata,” he says. “It might contain world coordinates, to units, to its divisions within the actual machine.”
What Slows Down Rapid-Prototyping
To those who are thinking about using rapid prototyping, Overy advises, “Either draw in 3D or in 2D--either one is fine. If we get 2D data, we can derive the 3D data from it in-house. But frequently, when we open the drawing, some of it is in 3D, some in 2D, some are snapped to 2D and some go all over the place.”
The company is in partnerships with Agtek, a civil engineering software maker, and 3D Nature, makers of Virtual Nature Studio. “We’ve worked with them to create a workflow and software that allow the colors, cuts and fills for virtual models to be printed. So what the designers see on the screen is precisely what is used to output,” says Overy.
For rapid prototyping, Laser Graphic Manufacturing uses Z Corporation 3D printers augmented by CNC operations. Cost ranges from $200 to $500 per square foot, depending on the level of detail desired and the amount of data cleansing and merging required.
ABOUT THE AUTHOR
Kenneth Wong is a former editor of Cadence magazine. He explores innovative use of technology and its implications in GIS Tech Trends and in Cadalyst magazine’s PLM Strategies column. Reach him at firstname.lastname@example.org.
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CA/NV/HI/GU Regional User Group Annual Conference
March 6–8, 2006
Waikiki Beach Marriott Resort & Spa, Honolulu, Hawaii
The conference theme, Kuleana a Laulima, Cornerstones for GIS, incorporates the Hawaiian concepts of responsibility and cooperation, as the geographic information systems community gathers to share information and support GIS efforts in the region.
Planning and Managing a GIS
March 18, 2006
Palm Springs, California
Preconference seminar at 2006 ESRI Business Partner Conference addresses planning and managing a geographic information system (GIS) in your organization. The seminar is designed for current or potential GIS managers and senior executives and is intended to bridge the communication gap between these two management levels.
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