A temporal, or time aware, analysis shows the impact of the proposed building's shadow at different times. Red connotes new shadow cast at noon, and blue represents shadows from existing buildings.

With the release of ArcGIS 10 and significant capabilities added to the ArcGIS 3D Analyst extension, the system becomes a truly 3D GIS. Working with a 3D GIS gives developers and city planners the ability to

• Analyze data and impacts not possible in 2D.
• Create models that drive critical decisions.
• Present and share realistic 3D scenarios with stakeholders, decision makers, and the public.

To speed the transition to planning cities and communities in 3D, the ArcGIS 3D Analyst extension now includes a Virtual City template.

A realistic 3D city model combines basemaps; imagery; elevation information; and objects, such as buildings and bridges. The virtual city model can also go belowground to include subsurface structures, such as basements, parking structures, subway systems, and utility infrastructure. Included template features of street furniture, vegetation, cars, and people seem to bring virtual cities to life.

A temporal element is added to create a window-by-window shadow analysis.

The Virtual City template uses Philadelphia, Pennsylvania, as a best practices model, walking users through step-by-step instructions on how to add elements to create a virtual city. There's also a tutorial on performing different types of 3D analysis.

Visualizing What-Ifs

The real power of ArcGIS 3D virtual cities comes in evaluating what-if scenarios. Concepts can be quickly visualized, evaluated, refined, or tossed aside depending on how a scenario plays out.

Tools built into the ArcGIS 3D Analyst extension help users assess the visual sensitivity of a proposed project or building, including changes to a skyline, effects of shadow on existing structures, and impacts on viewsheds and lines of sight for surrounding buildings.

Planners can analyze where the proposed building is casting new shadows, window by window, by time of day. Here windows colored red denote new shadow, yellow represents no shadow at all, and blue shows overlapping or existing shadow cast by nearby structures.

Take, for example, the impact of a proposed building in Philadelphia. In this scenario, planners can visualize and analyze the volumetric shadow the new structure will create. In 2D, planners could only determine that a shadow would be cast and where it would fall. With 3D volumetric analysis, they can perform more complex analyses that take into account time of day and existing shadows.

Other analyses can show the number of hours a day that any given window on a neighboring building will be in shade because of the proposed new building.

Although 3D virtual city models create visually compelling images to help communicate a vision or development concept, the real value is the depth of analysis that simply isn't possible in 2D.

More Information

For more information on the ArcGIS 3D Analyst extension and Virtual City template, including video demonstrations, visit www.esri.com/3D.