by Mark Hodges
Anyone who's ever managed a large business project-say, construction of a large office building-knows how difficult it is to stay abreast of daily progress by comparing reports, schedules, photos, figures, and spreadsheets. For decades, managers have created order from a welter of disparate data by using geographic information systems (GIS) software to intuitively organize and display a plethora of information according to its geographic location in space.
Typically, GIS users em ploy recognizable geography, such as a depiction of a building or a map of a city, to provide a spatial reference for the in for mation, enabling them to decipher and comprehend complex data more quickly and easily. As computer graphics and high-resolution imagery have be come more accessible and sophisticated, GIS users are "draping" visualizations over GIS maps to provide greater realism and im mediacy. Analyses generated by GIS applications are easier to understand when a computer-generated visualization can show the results in pictorial representations. 3D imagery offers an extra di mension of information-depth-that is often im por tant in quickly understanding problems or grasping obscure relationships.
Until recently, GIS portrayed the world from a 2D perspective, as if the earth were flat. But in the last few years, 3D display and analysis tools have become more widely accessible to mainstream practitioners at the desktop level, opening up new markets for a host of GIS applications. These new 3D GIS tools allow users to generate fly-throughs of high-resolution scenes for presentations and collaborative work, offering views from virtually any location. This capability would prove especially useful in siting facilities or equipment such as telecommunications towers, as well as for security planning at events such as the Olympics. In addition, 3D GIS enables users to see the results of volumetric analyses in concrete visual detail-for instance, by showing how high a city river would rise during a heavy rain, or how contaminants are distributed in an underground oil spill.
|By draping 3D imagery over GIS maps, users can easily organize complex data into compre hensive visual snapshots that can be viewed from various perspectives. |
Even so, the 3D maps, grids, and visualizations generated by the GIS software would have limited value if they were not harnessed to databases with extensive underlying information and analytical capability. By querying the properties of a single ob ject or inquiring about data relationships, such as which objects share a given trait or the proximity of two objects, users can make powerful analyses that otherwise would be difficult to achieve using just text and numbers, or 3D images alone. In fact, the merger of these databases with 3D visualization prompted one geologist to call GIS the "spreadsheet of visualization."
|Integral GIS used ESRI's ArcView 3D Analyst tool to optimize scheduling during the construction of Seattle's new Safeco baseball stadium. |
"The GIS market is rapidly evolving," notes Jerry Newton, GIS market segment manager in Compaq's Work sta tion Division, "and main stream users are discovering what they can do with 3D." This trend has not gone unnoticed by GIS soft ware manufacturers. The Envi ronmental Sys tems Re search Institute (ESRI), the leading GIS software maker, is forecasting a 30% annual growth in the 3D GIS mar ket, and is responding with new versions of established products for mainstream 3D GIS users.
For example, in late summer, ESRI plans to release a new version of its 3D Analyst for Arc View, the company's desktop GIS software package. The current 3D Analyst version provides a pull-down menu and tool buttons to create, analyze, and view surface data. The upcoming release will integrate ArcTIN, a tool for creating digital elevation models that's now an extension to ArcInfo 8, ESRI's high-end GIS software product. The new release will also offer enhanced capabilities for creating symbols, better realism through improved texture mapping, the facility to annotate maps with text, improved handling of large data sets, animation, and the ability to depict changes in GIS maps over time.
Intergraph, another leading GIS firm, is offering to desktop users GeoMedia Solutions Terrain, an extension to its GeoMedia software providing 3D terrain analysis, model generation, and construction of dynamic 3D fly-throughs. This extension includes an Active Terrain modeling tool that allows users to create objects, such as buildings, in 3D and place them into a rendered landscape.
|Prince William County (Virginia) used ERDAS Imagine GIS software to incorporate aerial photographs into a 3D map, which was used by area commissioners to review industrial development proposals. |
Meanwhile, ERDAS, the market leader in geographic imaging software, is focusing its efforts on the ability to drape high-resolution images over digital elevation models. The company's flagship software suite, ERDAS Imagine, integrates satellite imagery, aerial photography, and other remotely sensed data into mapping and GIS applications, while its Imagine VirtualGIS extension allows users to build 3D visualizations.
This month, ERDAS plans to release Stereo Analyst, a Windows-based 3D digital mapping system that will allow updating of existing models by users who lack training in photogrammetry (the science of making reliable measurements with photographs). Users wearing 3D glasses will be able to measure the three-dimensional properties of objects in stereo and insert them into GIS applications.
According to Mladen Stojic, ERDAS' photogrammetric product manager, Stereo Analyst will allow attribution of geographic features with qualitative data such as a building address, number of occupants, and zoning information, or quantitative data such as a building's area, perimeter, or height.
|Using CITYgreen, an application of ESRI's ArcView 3D Analyst, American Forest can quantify the impact of diminishing tree cover on local muni cipalities. The images to the right show the gradual decrease in urban tree cover in the Seattle area in 1972|
Another system for digitizing 3D information from imagery on the desktop is the Image Sta tion Stereo Softcopy Kit (SSK). This product is manufactured by Z/I Imaging, a photogrammetry and GIS company formed by Intergraph and Carl Zeiss.
Typically, most 3D GIS applications run on Intel NT workstations, as is the case with the ESRI, Intergraph, and ERDAS software. To get the most value from these and other 3D GIS tools, Compaq's Newton recommends using, at a minimum, a Pen tium III with a graphics accelerator.
Perhaps the most obvious use for 3D GIS is as a planning tool for the construction of large and complex facilities involving multiple subcontractors, managers, and clients. GIS provides a single medium for showing how many pieces of a project relate to one another and the job as a whole.
For example, when the Marine Corps Air Station in El Toro, California, closed, the Orange County Board of Commissioners hired Psomas, Inc. (Costa Mesa, CA) to develop a GIS to help them plan for construction of a regional airport on the base. The resulting application merged information on noise impact, facility designs, data about surrounding properties and demographics, and traffic analysis. This information was embedded into a three-dimensional model Psomas built with the ArcView 3D Analyst that contains imported aerial photography and rendered site topography and buildings. The realism of the visualization has been useful in marketing base facilities for commercial leasing, says Daniel McCroskey, Psomas project manager.
GIS also proved its value as a management tool during the con struction of Seattle's new Safeco baseball stadium. Integral GIS (Seattle) used ESRI's ArcView 3D Analyst for logistics planning to visualize the impact of various subcontractor schedules on the timetable for the entire project. "You can look at snapshots of schedules in 2D or 3D space and watch how the stadium gets built," says Patrick Moore, In tegral GIS director. "At first people would say, 'That's cool.' But when I showed them what the GIS could do, they would say, 'That's not a toy. We can use it to do things.' Looking at things in 3D saves quite a bit of money." In fact, GIS could provide a living record of a facility's construction, which could be used to assign responsibility if schedules aren't met, he adds.
|These fly-through views of Capetown, South Africa, were produced with ERDAS Imagine's VirtualGIS, which lets users determine visibility from any perspective in a computer-generated landscape.|
One of the early uses of 3D GIS tools has been for land planning by governmental agencies. Prince William County, Virginia, re cently purchased ERDAS Imagine software to generate 3D maps from the county's collection of aerial photography to create a fly-through of the coastline along Belmont Bay. The visualization aided the county supervisors in reviewing proposals for high-tech industrial development.
Using the software, Kathy Prescott, chief of the county's GIS Division, placed visualizations of dif ferent land tracts in a spatial format that could be easily navigated in a seamless context rather than viewed in dozens of separate site photos. The fly-through provided the supervisors with a three- dimensional perspective of the entire area and allowed them to move from site to site, looking at land parcels under consideration from every direction. "It was effective in getting the point across," she says.
According to Prescott, the county is just starting to use 3D GIS and has not yet incorporated conventional GIS analysis into its fly-throughs, though Prince William County plans to integrate 3D visualization tools into its day-to-day GIS program, with economic development as the most valuable application of the technology. Prescott's office is also starting to use the software to study the visual impact of proposed radio-tower siting locations in neighborhoods. "We realize we're just touching the tip of the iceberg," she notes. "I see 3D GIS becoming as routine as the rest of our GIS."
One of the reasons why urban plan ners are drawn to 3D GIS is its ability to highlight cause-and-effect re lationships that are slow to develop and hard to recognize. For instance, American Forests, a nonprofit conservation organization based in Wash ing ton, D.C., processed a variety of satellite images to illustrate the decrease in tree coverage resulting from urban sprawl in several US metropolitan areas.
|A 3D GIS map from the recent Alaska Airlines crash off the California coast displays various information, such as water depth, at the site of the accident. |
The resulting ERDAS Imagine visualization allowed Amer ican Forests to analyze the impact of these changes when used in conjunction with CITYgreen, an ArcView GIS application that estimates the dollar value of tree losses according to established engineering and scientific formulas. With CITY green, the group intuitively showed one consequence of this forest-cover loss: Cities and counties had to build new storm-water management facilities to replace the water storage previously provided by trees.
To further illustrate its point, the American Forests organization constructed a 3D fly-through of the Puget Sound, Wash ington, area by draping low-level aerial photography over a digital elevation model. The underlying reason for the fly-through, explains Gary Moll, the group's vice president, was so "the novice who may not understand the abstract GIS models could visualize what we've seen."
Another burgeoning market for 3D GIS is natural resource management-from monitoring beach erosion to visualizing subsurface geology-for which accurate volume measurements are required. Such terrain mapping proved extremely useful for Daniel B. Stephens & Associates of Albuquerque, New Mexico, which used the ArcView 3D Analyst to map contaminated subsurface soil in an environmental litigation case.
The attorneys for one party in the dispute wanted to assess liability, so the Stephens consulting firm integrated hundreds of soil samples at the EPA Superfund site into a 3D GIS map. The subsurface contaminants were color-coded, with surface features rendered as primitive graphic objects. The user could click on any area of contamination and call up database information such as the sample's concentration, type of chemical compound, and date of collection. Despite the graphic simplicity of the map, the attorneys found it valuable because they could look at all the data at once, says David Jordan, manager of GIS services at Stephens & Associates.
|A GIS building map of the Oklahoma City federal building let researchers analyze the correlation between the severity of victims' injuries and their location at the time of the bombing.|
Jordan is also using 3D GIS tools to address the con tamination of rainwater as it washes over the large stockpiles of waste rock (often the size of small mountains) left behind by mining companies. Although regulators would like to grow vegetation on these waste rocks to minimize acidic water runoff from the rock, the slopes are usually too steep to sustain soil and plant cover. Ste phens & As so ciates is developing an Arc View 3D Analyst application that vi sualizes and analyzes re-grading proj ects. The GIS scene viewer will show how much waste accumulates in the "footprint" at the base of rock or if projected acidic rainfall levels change as its slope is sheared.
GIS technology is likewise well suited for emergency response. In a typical accident or natural disaster, representatives from various governmental units must collaborate, but clear communication often becomes difficult. One reason is that scenes of natural disasters and serious accidents are often difficult to examine because they are obscured by smoke or are located under water or at inaccessible locations. Geographic information systems can organize remotely sensed data into a comprehensive view of the disaster scene. GIS recently proved its mettle in this respect when it was used by Geo Insight International (Ojai, CA) to produce an underwater map of the site of the Alaska Airlines Flight 261 crash off the California coast in late January.
To create a 3D GIS of the scene, Geo Insight input remotely sensed data into ERDAS Imagine. The visualization of the ocean floor around the airliner was then used in map form by the news media, and would have been helpful in the search for the flight recorder if the device had not been found so quickly, says David Zubak, a remote sensing specialist at Geo Insight International. The purpose of the application was to depict the undersea crash scene, but Zubak says emergency responders could have used it to gather information about water temperature, current speed, and water depth-measurements that would have been useful in predicting the movements of the aircraft debris.
A geographic information system also provided ep idemiologists with a tool for an after-the-fact assessment of the 1995 Oklahoma City terrorist bombing. Working for the Oklahoma Department of Health, Integral GIS used the Arc View 3D Analyst to create a 3D map of the Alfred P. Murrah Federal Building and its immediate neighborhood. The purpose of the GIS building map was to help researchers study the injuries suffered by people in various parts of the building and in the surrounding neighborhood. According to Patrick Moore, the company is expanding the tools developed in this study for security planning prior to the 2002 Olympics in Salt Lake City.
Without a doubt, early users of 3D GIS are benefiting from the technology, and researchers and manufacturers are working to resolve the current shortcomings-the most commonly cited being the need for better visual realism. Current software products lack the capability to create ob ject shapes or textural features so that they resemble objects in the real world, not geometrical blocks. The new products from ERDAS and ESRI are enhancing texture mapping, and ERDAS hopes to release software by year's end that improves the fitting of photographic imagery on underlying models.
Another challenge is the need to increase the 3D data sets available for use in geographic information systems, "especially high-resolution buildings and surface models," says David Maguire, director of products at ESRI. Although digital elevation modeling software measures the Z coordinate of objects, it actually produces 2.5D models because height information does not depict overhangs and openings in walls.
However, these problems are beginning to be resolved, as national mapping agencies and companies collect 3D data sets. Also, GIS builders can collect true 3D information on their own with new tools such as ERDAS Stereo Analyst. With more realistic 3D imagery on which to base their analyses, researchers will be able to solve volumetric problems with a higher degree of accuracy.
Slow processing speed is another limitation affecting 3D GIS systems with memory-intensive visualizations, such as those with fly-through renderings. The solution, says Nick Faust, associate director of Georgia Tech's Center for Geographic In for mation Systems, is to improve the paging of data in GIS software so that objects are rendered with appropriate levels of resolution from the foreground to the background. This is a complex programming task for fly-arounds, in which users are constantly changing vantage points, that could be eased through better data management and rendering algorithms.
|The ActiveFlight feature in Intergraph's GMS Terrain software lets users produce dynamic fly-throughs of the data. |
None of these technical problems appears insurmountable or has stalled efforts to create more innovative uses of GIS. Geo graphic information systems soon will be four-di men sional-that is, the software will create maps that change over time, as GIS becomes capable of real-time tracking when linked to global positioning system satellite data streams. With more digital information becoming available, users will even have tools to build virtual cities. But perhaps the most eagerly awaited innovation is the ability to display 3D GIS information over the Web and to improve collaboration at a distance. (Web integration will depend on enhancements outside the control of GIS manufacturers, such as improved bandwidth, data compression, direct data streaming, and enhanced client/server technology.)
As geographic information systems become more powerful and pervasive, they will offer users a chance to see what information means at a glance, rather than requiring them to spend so much time deciphering text and numbers. And with 3D GIS, we'll have more opportunities to view data in the same depth with which we see the world. Mark Hodges is a Computer Graphics World contributing editor based in Atlanta. He can be reached at firstname.lastname@example.orgDesktop GIS SOFTWARE
Environmental Systems Research Institute (ESRI)