Collaborative Geographic Visualization

Theresa Marie Rhyne & Thomas Fowler*
Lockheed Martin Technical Services
United States Environmental Protection Agency
Research Triangle Park, North Carolina 27711
trhyne@vislab.epa.gov

(*now at Nortel (Northern Telecom) Corporation)

Introduction:

At the United States Environmental Protection Agency (US EPA), efforts are underway to integrate the agency's geographic information systems (GIS) , scientific visualization (SciVis) and World Wide Web (Web) suite of tools for comprehensive environmental decision support. The EPA's National GIS Program Office is the focal point of EPA's efforts to implement a consistent Agency-wide spatial data management infrastructure. One result of these efforts is the EPA Spatial Data Library System (ESDLS) which is currently accessible via the Web at (http://www.epa.gov/ngispr/esdls.html). ESDLS utilizes the Environmental Systems Research Institute's (ESRI) ARC/INFO data management software (entitled Librarian) and complies with Spatial Data Transfer Standards. The ESDLS is EPA's node on the Federal Geographic Data Committee (FGDC) 's National Geospatial Data Clearinghouse (see: (http://nsdi.epa.gov/nsdi)).

During 1996 and 1997, techniques for providing real time visualizations of spatial data sets for the ESDLS were explored. The EPA's Scientific Visualization Center, in collaboration with the agency's GIS support team, conducted initial evaluations of software that integrates visualization toolkits (i.e. the Application Visualization System (AVS)) and geographic information systems (i.e. ESRI's ARC/INFO). Web user interfaces to GIS and SciVis file servers were also successfully implemented. This discussion highlights our efforts to provide effective two and three dimensional visual displays of spatial data sets. Using Web tools, we also investigated the use of QuickTime Movies, Java applets, and the Virtual Reality Modeling Language (VRML) as techniques for enhancing the presentation and exploration of geographic visualizations.

Integrating GIS & SciVis Tools:

AVS-ARC is a set of customized modules for the Application Visualization System (AVS 5.0) from Advanced Visual Systems. These modules directly access ARC-INFO spatial data sets and move them into AVS for three dimensional (3-D) visualization and animation purposes. Successful implementation of AVS-ARC involves syncing the ESRI ARC-INFO license manager with the AVS Inc. license manager. Once this system administration task is completed, the AVS-ARC modules can be connected to other standard AVS modules to build a visualization network. The ARC- INFO files and data do not need to co-exist on the same machine as AVS. AVS-ARC supports remote file server access across a telecommunications network (i.e. via NFS and TCP/IP protocols).

Using AVS-ARC, ARC Grid files containing multiple source sliced classification data were imported into AVS and displayed in the AVS Geometry Viewer. The AVS-ARC modules converted and registered the Grid data into AVS Field format. An AVS generated colormap was associated with the field data. The 2-D field data was then draped over a 3-D field generated from another ARC Grid dataset containing elevation data. All of this was converted into AVS geometry in the Geometry Viewer. The visualization results of these efforts can be seen on the Web at (http://www.epa.gov/gisvis/products). The example spatial data shown relates to the geographic region pertaining to the Great Smoky Mountains National Park and other parts of eastern Tennessee and western North Carolina in the United States.

We also merged geo-referenced image files with 3-D graphics displays. As an example, we created a TIFF file by scanning a portion of a USGS 100K series topographic map of a geographic area including Sevierville and Pigeon Forge, Tennessee. The TIFF file was imported into ARC/INFO and converted into an RGB grid stack. Using AVS-ARC, the Grid data stack was converted into AVS field format. We followed the same process outlined above for draping the 2-D field data over a 3-D field generated from elevation data. Using standard AVS modules, we also generated animation and fly-by sequences of this data set. For display on the Web, we converted the AVS based animations into Quick Time movies. Results of these texture mapping efforts can be seen at: (http://www.epa.gov/gisvis/texture).

Figure # 1: Integrated AVS - Arc Info system. Research conducted at the US EPA Scientific Visualization Center, Thomas Fowler and Theresa-Marie Rhyne / Lockheed Martin Technical Services.

Displaying GIS-SciVis Results on the Web:

A Web site for our GIS-SciVis integration project was developed to facilitate sharing and discussion of 3-D geographic visualization techniques, (http://www.epa.gov/gisvis). We named this site "GIS- VIS". These efforts are located on the same Web server as the Web site of the EPA Spatial Data Library System (ESDLS) developed by the EPA National GIS Program Office.

The 3-D static images developed in AVS were rendered on a Silicon Graphics Reality Engine workstation and converted to JPEG format for display on the Web. The XV utility for UNIX workstations, developed by John Bradley, was used to convert Silicon Graphics "RGB" files to JPEG format. AVS based animations were converted into Quick Time movies. This was done by converting each of the AVS movie files into Silicon Graphics "RGB" format. Once in "RGB" format, we used the Silicon Graphics "Movie Convert" utility to create a Quick Time movie. We chose the Quick Time movie format over MPEG to provide for the addition of supporting audio narration of the movie.

Figure # 2: Example of a Web page for collaborative geographic visualization & integration (http://www.epa.gov/gisvis). This Web site was developed for the U.S. EPA by Lockheed Martin.

The "GIS-VIS" Web site was also designed as a teaching tool. To support technology transfer activities, we created a slide show describing how geographic visualization supports moving from "flat" maps to 3-D displays and animations. The slide show functions were developed with a Java applet. Due to security concerns, Java is presently not in use on the EPA's public domain Web server. We also explored how to combine GIS-SciVis integration with the recently developed Virtual Reality Modeling Language (VRML).

Going Virtual with GIS-SciVis Integration:

VRML is a newly created programming language and standard for building three-dimensional objects (often called "worlds") on the Web, see: (http://vag.vrml.org/). These 3-D worlds can be viewed on any computer with Web browsers that support the VRML standard. For our efforts, this means that users, especially the general public, with a VRML browser will be able to interact with 3-D displays of spatial and terrain data sets.

Our first set of VRML 1.0 worlds were built using an AVS module developed by our colleagues at the United States Geological Survey (USGS) see: (http://vineyard.er.usgs.gov/). This AVS to VRML 1.0 module allowed us to convert our AVS-based GIS-SciVis geometry files into VRML files. We successfully converted terrain models where the original data source were ARC/INFO Triangulated Irregular Network (TIN) files. An example can be found at (http://www.epa.gov/gisvis/vrml), under ARC->AVS->VRML.

The process of moving from ARC/INFO to AVS to VRML was found to be cumbersome and not always successful. As a result, we began working on a technique that allowed us to move ARC/INFO data sets directly into VRML. We successfully converted TINS, point, line and polygon coverages into large ASCII files that produce VRML 3- D worlds. We developed utilities that work partially within ARC/INFO (AML scripts) and independently (C++ code developed under UNIX) of the GIS environment. These tools convert ARC/INFO data sets into VRML 1.0 & 2.0 worlds.

TIN data sets have Z-values that can be converted from an interchange format. Points, lines and polygon coverages in ARC/INFO are 2-D data sets that require Z-values to be interpolated in conjunction with an elevation grid or TIN structure. Our utilities allow for most ARC/INFO data sets and analysis products to be converted into VRML. We also built a tool that creates multivariate prism maps of ARC/INFO polygon data. This allows for mapping one variable as the height of the map features and another variable as the colormap.

Using the VRML 2.0 standard (released in August 1996), we further developed VRML worlds that incorporate animation functions. One example includes VRML worlds of digital elevation model (DEM) data where the Z-values change over time. These examples can be found at: (http://www.epa.gov/gisvis/vrml2.html). Java user interfaces were developed to allow for: (a) selecting DEM data sets and establishing color maps and (b) Creating customized fly-bys of DEM data sets. JPEG images of these user interfaces can be found at: (http://www.epa.gov/j03svcpb/modeling/terrain.html).

Figure # 3: Example of a VRML 2.0 file from a Digital Elevation Model (DEM) animation on the (http://www.epa.gov/gisvis) site. This Web site was developed for the U.S. EPA by Lockheed Martin.

Future Directions:

We are currently expanding our horizons to explort the 3-D visual display and animation of data mined from ESRI's recently released Spatial Database Engine (SDE) product. For more information on SDE see: (http://www.esri.com/base/products/sde/sde.html). We anticipated using SDE in conjunction with the AVS Express visualization environment from AVS. Work will continue on our VRML 2.0 efforts for ESRI ARC/INFO and SDE data sets. Discussions are underway with the EPA National GIS Program Office to provide for the integration of their EPA Spatial Data Library System (ESDLS) with our geographic visualization techniques. We hope to provide general users with utilities that allow for creating VRML worlds from interactive queries of ESDLS data. Java based Web interfaces to support this integration and to provide for the technology transfer of these new geographic visualization techniques will also be developed.

Acknowledgments:

We would like to thank Lockheed Martin Technical Services and the Enterprise Technology Services Division (ETSD) of the United States Environmental Protection Agency (U.S. EPA) for supporting our GIS-SciVis Integration project. Special thanks to Don Block, Mark Bolstad, Dudley Bromley and Tom Scheitlin of Lockheed Martin as well as Lynne Petterson. John Shirey, and Stephen Fogarty of the U.S. EPA. Scott Sandall of Advanced Visual Systems Inc. provided us with beta AVS-ARC software. John Evans and Richard Signell of the U.S. Geological Survey shared with us their AVS to VRML module.

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