How Envision Tomorrow Works
It's Not as Complicated as It Seems
Envision Tomorrow may seem very complex to the new user. However, understanding a few key elements of its architecture will allow the user to quickly feel comfortable enough to dive into the details.
The Brains are in the Spreadsheets
Planners know spreadsheets, not code. For this reason, Envision Tomorrow has kept most of the calculation elements in a scenario spreadsheet that is linked to ArcGIS via an extension. Modifying assumptions – and even adding new indicators – is far easier within a spreadsheet than within lines of code. In addition, the tool has an unparralleled level of transparency since each of the equations are visible and easy to change by the user.
A Linked System of Spreadsheets
There are three basic types of spreadsheets involved in the interlinked Envision Tomorrow platform. Each is based on a standard template, accessible from the downloads section of this website. The three spreadsheets include the building-level Prototype Builderspreadsheets, the scenario-level Scenario Builder spreadsheet, and individual modular models that can be dynamically linked to the scenario spreadsheet, such as the Fiscal Impact Model and the Travel Models.
The smallest unit of analysis in our scenarios are buildings. Individual buildings are modeled in a template spreadsheet called a Prototype Builder. This template spreadsheet is a simplified, planning-level pro forma, not unlike one used by a developer to evalulate the financial feasibility of a development project. The Prototype Builder includes both the physical attributes of buildings, such as height and landscaping, and also the financial attributes, such as rents and construction costs.
The Prototype Builder is a handy stand-alone tool for evaluating the financial feasibility current or proposed zoning. It also serves as the template for creating a library of building types to be used in any scenario planning process. Depending on the scale of the scenario planning effort, a Prototype Library could include only a handful of generic, or "prototypical," building types to a library of 40-50 very specific biulding types. This library of building spreadsheets are loaded into the Scenario Spreadsheet through the use of a push-button macro within the Scenario Spreadsheet. Once loaded, each building spreadsheet is dynamically linked to the Scenario Spreadsheet. This means that if the user edits any of the building spreadsheets, the changes are automatically reflected in the Scenario Srpeadsheet, and thus, the Scenarios themselves.
The ESRI ArcGIS Extension
The Envision Tomorrow extension for ESRI's ArcGIS is a relatively simple interface that allows users to select and "paint" different land use types, or Development Types, onto the scenario layer. The extension is also responsible for establishing a dynamic connection to the Scenario Spreadsheet, so as the user paints, information about how much area the user has painted is sent to the Scenario Spreadsheet, which in turn, results in changes in the indicator charts and graphs. The file menus in the ET extension also contain the various ET Analysis Tools wizards explained further under the Analysis Tools section.