Issue link: https://read.dmtmag.com/i/35322
geometric information is instantly reported. Running a query to find the length of centerline, the conventional design requires 7,461 linear feet of street. When a query is run on length of curb, the conventional plan indicates 13,910 linear feet. The Prefurbia plan results in 4,974 linear feet of street (33 percent less) and 11,435 linear feet of curb (18 percent less). Real Reporting A query of linework length isn’t the same as geospatial reporting. The geospatial information is given a color or texture (textures provide a better-looking presenta- tion) to provide a dynamic presentation, but it’s also tagged as being impervious or pervious. When developing land, impervious surface area is a snapshot of manmade elements that have environmen- tal and economic impacts. The ratio of organic site area to this manmade surface area is called environmental or economic density (ED). The lower the ED, the lower the environmental and economic costs of development. Figure 4 includes the conventional-plan ED chart (top) derived by the arcs and lines that would define the built environment. Approximately 58 percent of the site is organic, and it provides a precise breakdown of each lFigure 5. A before-and-after plan is shown from the same vantage point in a virtual-reality window. manmade surface in order of its impact on the natural ground. The area of single-family homes is the largest impact, consuming 22.8 percent of the total land mass, with public street consuming 10.8 percent of the area. The figure’s lower portion provides the plan’s man- made impact using Prefurbia methods. The overall impact on the site drops from 42 to 37.5 percent. Note that the surface area of public walks drops from 2.8 to 2.1 percent, although the walks in the Prefurbia plan are 50 percent wider. This is because of the lower street lengths and walks placed on one side of the street where traffic is low. Sustainability over Density Precision geospatial information tied to textures allows presentations that are more realistic. Geospatial data that can be shadowed and have transparencies applied make CAD drawings look obsolete, but add less than a minute total to the workload of plan production. Geospatial data tagged as impervious or pervious allow automatic compilation of precise environmental and economic impacts. In addition, rough construction- cost estimates can be accomplished by tagging preci- sion geospatial data (and layers) to specific items. Precision spatial areas can have height and separate wall textures for virtual-reality abilities. Without the ability to instantly report precision spa- tial data through modeling of experimental land-use configurations, Prefurbia wouldn’t be possible. And simply reaching a target density isn’t necessarily the best way to improve profitability, livability and environ- mental impact. Adhering to minimums might achieve density, but exceeding minimums can accomplish the same and achieve sustainability. lFigure 4. The environmental/economic density of the original plan (top) is compared to a Prefurbia neighborhood (bottom). Rick Harrison, land planner, author of Prefurbia and developer of PPS, is president of Rick Harrison Site Design Studio and Neighborhood Innovations LLC; e-mail: rharrison@rhsdplanning.com. JUL Y 2O11 / WWW . GEOPLA CE . COM 25