3D GIS: A Technology Whose Time Has Come
4
T he very first output from a GIS came from a line printer attached to a large mainframe computer. Us- ing individual letters (e.g., “W” for water) or over-striking letters, line printer grayscale maps began to show the patterns and results of the first GIS analyses. In these pioneering years, 3D presentations were not viable due to the limitations of computer performance. Fast-forward 30 years and we have the ability to create dynamic 3D GIS presen- tations on laptop computers. While it may be too early to herald the end of the plotter in favor of a vir- tual display, it is very clear that use of 3D GIS to illustrate and analyze our GIS data is growing. Also likely to succumb to the power of the virtual, 3D GIS dis- plays are the static architectural render- ings used to present proposed develop- ments. Figure 1 illustrates the power of 3D GIS in the visualization of a proposed new office building. For years, we in the GIS community have assumed that everyone viewing our work understood the 2D display of Figure 1 The original architectural drawing of a proposed office building (left) and the same building rendered in a 3D GIS display (right) with the mountains from a digital elevation layer in the background. Note that the black and white architectural 2D site plan has been scanned, registered, and draped over the terrain model. Unlike the drawing, the GIS presentation can be viewed from any location in the scene. information. In reality, we all knew bet- ter and as those that have started using 3D to present their analyses can attest, a virtual environment is very convincing in public meetings. The world around us is three-dimensional and it seems natu- ral that presentations of GIS data should move in this direction. How many times have we looked at a zoning map forget- ting that zoning also has a height com- ponent? Transitioning to 3D GIS need not be an arduous task. Quite the oppo- site is true. This article is a basic primer to help one get started in the 3D arena. Beginnings Serious use of 3D in GIS started about five years ago with products like Evans & Sutherland’s RapidSite product (no longer available) and MultiGen-Par- adigm’s SiteBuilder 3D extension to ESRI’s ArcView. Both of these companies are principally involved in the creation of simulators and supporting software. They saw their technology in GIS as a logical extension of their expertise. These and other products successfully delivered compelling 3D presentations but their acceptance by the greater GIS audience was limited. Arguably, the introduction of ArcGIS version 9 with the 3D Analyst extension has done more to fuel the growth of 3D GIS than any other software release. Almost over night, thousands of GIS users were given A Technology Whose Time Has Come Gary Smith and Joshua Friedman DISPLAYED WITH PERMISSION • Earth Observation Magazine • November 2004 • www.eomonline.com • ALL RIGHTS RESERVED
Transcript of 3D GIS: A Technology Whose Time Has Come
The very first output from aGIS came from a lineprinter attached to a largemainframe computer. Us-
ing individual letters (e.g., “W” forwater) or over-striking letters, lineprinter grayscale maps began to showthe patterns and results of the first GISanalyses. In these pioneering years, 3Dpresentations were not viable due to thelimitations of computer performance.Fast-forward 30 years and we have theability to create dynamic 3D GIS presen-tations on laptop computers.
While it may be too early to heraldthe end of the plotter in favor of a vir-tual display, it is very clear that use of3D GIS to illustrate and analyze our GISdata is growing. Also likely to succumbto the power of the virtual, 3D GIS dis-plays are the static architectural render-ings used to present proposed develop-ments. Figure 1 illustrates the power of3D GIS in the visualization of a proposednew office building.
For years, we in the GIS communityhave assumed that everyone viewing ourwork understood the 2D display of
Figure 1 The original architectural drawing of a proposed office building (left) and the same building rendered in a 3D GIS display (right) withthe mountains from a digital elevation layer in the background. Note that the black and white architectural 2D site plan has been scanned,registered, and draped over the terrain model. Unlike the drawing, the GIS presentation can be viewed from any location in the scene.
information. In reality, we all knew bet-ter and as those that have started using3D to present their analyses can attest,a virtual environment is very convincingin public meetings. The world around usis three-dimensional and it seems natu-ral that presentations of GIS data shouldmove in this direction. How many timeshave we looked at a zoning map forget-ting that zoning also has a height com-ponent? Transitioning to 3D GIS neednot be an arduous task. Quite the oppo-site is true. This article is a basic primerto help one get started in the 3D arena.
BeginningsSerious use of 3D in GIS started
about five years ago with products likeEvans & Sutherland’s RapidSite product(no longer available) and MultiGen-Par-adigm’s SiteBuilder 3D extension toESRI’s ArcView. Both of these companiesare principally involved in the creationof simulators and supporting software.They saw their technology in GIS as alogical extension of their expertise.
These and other products successfullydelivered compelling 3D presentationsbut their acceptance by the greater GISaudience was limited. Arguably, theintroduction of ArcGIS version 9 withthe 3D Analyst extension has done moreto fuel the growth of 3D GIS than anyother software release. Almost overnight, thousands of GIS users were given
A TechnologyWhose Time Has ComeGary Smith and Joshua Friedman
DISPLAYED WITH PERMISSION • Earth Observation Magazine • November 2004 • www.eomonline.com • ALL RIGHTS RESERVED
the capability to create 3D presenta-tions complete with realistic buildings,trees and other landscape objects. ESRIwas certainly not the first to make thispossible, but its market penetration andnumber of installations stand to hastenthe transition to 3D.
3D Analyst version 9 comes with anextensive array of 3D symbols (buildings,trees, etc.) but does not include softwarecapable of building custom features. Forthe creation of custom buildings, trees,and landscape features, users must turn toother third party software solutions. Whilethis does add slightly to the cost of get-ting started, GIS users will find the expo-sure to software from other 3D environ-ments very stimulating and informative.
ESRI and 3DWhen it was released earlier this year,
the ESRI software could import 3D fea-tures in OpenFlight (popular in simula-tions), 3D Studio (popular in game, ani-mation and architecture) and VRML (popular on the Web) formats. Withinweeks of the official release of ArcGISversion 9, @Last Software, maker of
SketchUp software, and ESRI releasedfree plug-ins that enable SketchUpmodels to be imported directly into 3DAnalyst as either symbols or multi-patch features.
As a symbol, an object can only beused for visual purposes. The multi-patch is a shape type stored in an ESRIshapefile. It can store attributes andparticipate in geoprocessing operationsas well as be used as a symbol. Inshort, a building model, imported as amultipatch, is a feature just like a par-cel polygon is a feature in a parcel GISlayer. The multipatch may very wellprove to be the key format that allowsvirtual 3D objects to be “smart,” justlike all other GIS layers.
Within the past few weeks word hassurfaced that Graphisoft, maker ofArchiCAD, and ESRI have created aninterface for exchanging informationbetween ArcGIS and the Virtual Buildingenvironment of ArchiCAD. It seems logi-cal that other component building anddesign software packages will soon fol-low. Many already export into one of thesupported file formats.
Working in 3DConstructing a 3D scene is a delicate
waltz between the incorporation ofextensive detail and the need to main-tain an acceptable level of computerperformance. A 3D GIS operates in a run-time environment just like the computergames and simulators. This environmentallows users to travel anywhere in thescene at any time. This is in stark con-trast to the animation quality moviesthat can take hours to render singleframes and only follow a specified tract.
To create an efficient 3D environ-ment, buildings may be constructed as awire frame and textured with digitalimages to dramatically reduce the num-ber of polygons drawn by the computerwithout losing their character and visualappeal (Figure 2). Careful use of shad-ows can provide the illusion of detail inthe building model.
Building TreesTree models are usually composed of
two or more intersecting polygons witha picture of a tree pasted on all sides.However, for trees that will only be
Figure 2 Working from 2D footprints, building models are constructed as a wire frame, textured from digital images, and completed forinclusion in the 3D GIS environment.
DISPLAYED WITH PERMISSION • Earth Observation Magazine • November 2004 • www.eomonline.com • ALL RIGHTS RESERVED
Taking 2D GIS to 3DBuilding an existing GIS database
into a 3D environment might seem like adaunting task. Attempted all at once,such an undertaking might prove over-whelming. Incremental work and con-centration on important regions canlessen the data development effort.Commercial growth centers, downtownredevelopment areas and critical visualresource areas are all logical startingpoints for building 3D scenes that couldultimately cover an entire GIS database.
New technologies like the High Defi-nition Survey (HDS) equipment (alsoknown as 3D laser scanning) appear tooffer a substantial time saving methodto capture the “as built” environment.HDS is a LiDAR scanner on a tripod andthe points it generates from its laser
Figure 3 The steps involved in the creation of a tree symbol: starting with a photograph, extracting just the tree, creating the model withtwo polygons, and finally positioning the tree on the virtual landscape.
Figure 4 A building can be modeled in both its exterior presentation and with its interior detail by storing each floor of the building as amultipatch. This allows the GIS to treat each floor as a layer and store separate attributes related only to that floor.
viewed from a distance, a single polygonthat uses a lower resolution photo willprovide the same visual effect whilereducing the graphic impact of thescene. Figure 3 illustrates the construc-tion of a green ash tree for use in a 3DGIS environment.
More 3D visualization environmentsnow support models or symbols thatincorporate levels of detail (LOD), whichcan help improve performance whilemimicking what can or cannot be seenwith the human eye. For example, amodel of a road sign built with LOD mightuse a detailed texture at close range butswitch to simple colors when viewed froma significant distance.
Creating a tree model is actuallymuch harder than it looks. The processof extracting a tree from a full digital
picture to create a texture can be a timeconsuming process. Issues of lighting,feature extraction, size and formattingcan account for hours of work. Yearsago a French company, Bionatics, recog-nized the tedious nature of virtual treecreation and sought a mathematicalsolution to this process. The result wasa product called RealNAT that haslargely replaced manual tree model cre-ation within the simulator industry.Working from a mathematical seed thatis species specific, the software growstrees to a specified age and seasonaldepiction. Saving a tree at differentages or seasons allows for a temporaldisplay that can illustrate change overtime. Seeds can be used over and overagain, each time producing a slightlydifferent appearance.
DISPLAYED WITH PERMISSION • Earth Observation Magazine • November 2004 • www.eomonline.com • ALL RIGHTS RESERVED
striking objects can be used to constructexisting features.
3D GIS: Future VisionImagine a public meeting where a
proposed building is added to a vir-tual, GIS-enabled landscape. The GISimmediately evaluates the new build-ing for compliance with use constraintsas well as setback and height restric-tions. The water and waste water sys-tems are connected to the outsidelines (GIS layers) to verify capacityavailability. Stormwater run-off fromthe roof and other new impermeablesurfaces are evaluated and summa-rized. Security and emergency vehicleaccess (including turn around space)are considered from all access routes.Finally, the reviewers can evaluate theappearance and compatibility of thenew structure from any vantage pointwithin the existing virtual environ-ment. By substituting larger tree mod-els for the initial planting stock, it ispossible to anticipate the appearanceof the area at some time in the future.
Consider an untapped resource—high school CAD and computer anima-tion students who might jump at thechance to create 3D environments. Foryears the geospatial community hasworked to bring GIS to the K-12 agegroup. This audience has grown up withcomputer games and the use of 3Dgame-like environments to facilitatelearning and community involvement
would seem like a natural match. Letthem help create the 3D environmentfrom field measurements and thenenjoy the fruits of their labors.
Expect the opportunities for employ-ing 3D GIS technology to expand at arapid rate over the next few months andyears. Officials are already looking at 3Dbuildings by floor or even by room inapplications related to security andemergency planning. Figure 4 shows thefirst floor of a school as a multipatchfeature with the roof and second floorturned off in the display. With detailedterrain and land cover information canwe better model both the visual impactand performance of proposed wind tur-bines on our hillsides? Viewsheds fromthe windows of both existing and pro-posed buildings are now possible inboth in a quantified and visual simula-tion. In reality we have just brushed thesurface and exposed only a fraction ofother possible technologies that may beapplicable to GIS.
About the AuthorsGary Smith and Joshua Friedman
are part of Green Mountain GeoGraph-ics, Ltd. a GIS consulting firm that wasfounded in 1988. They have been work-ing extensively in 3D GIS for more thansix years and publish an informal 3DGIS newsletter targeted at the users ofArcGIS and related technologies. Theycan be reached at www.gis-help.com [email protected].
Resources
Details on multipatch feature typehttp://www.esri.com/library/whitepapers/pdfs/shapefile.pdf
@Last SketchUp (allows creationand editing of multipatch features,demo available)http://www.sketchup.com/gis
MultiGen-Paradigm ModelBuilder3D (wizards help users create efficient symbols) http://www.multigen.com/products/3d_gis/sitebuilder/modelbuilder3d.shtml
Bionatics RealNAT (create newtrees in minutes)http://www.bionatics.com
High Definition Survey (alsoknown as 3D laser scanning)http://hds.leica-geosystems.com/
DISPLAYED WITH PERMISSION • Earth Observation Magazine • November 2004 • www.eomonline.com • ALL RIGHTS RESERVED
