Scenario 360 provides three decision tools (one optional) that help you model future growth. Here is some information about how these tools compare and how they can be used together.
Build-Out calculates building capacity, or potential future building numbers and locations.
Given potential future building numbers and locations, TimeScope calculates which buildings will be built when.
And given potential future building capacity and a target number of buildings, Allocator estimates where that number of buildings will be appear based on probabilities associated with the desirability of potential building polygons. (Allocator is an optional tool that may require separate licensing.)
A useful analogy for these tools is passengers taking seats on a subway train.
Build-Out calculates the number of useable seats on the train. You might think of train cars as land-use zones, and density rules as specifying how closely the seats are placed in each car. Land-use constraints like “no building in wetlands” correspond to rules like “no seats close to emergency exits” and affect the actual number of seats you can place in a car.
TimeScope shows how the seats are taken up as passengers board the train. It illustrates both how rapidly the seats fill up and the order in which they are taken. It uses deterministic rules to decide the order in which seats are taken up. An example rule would be, “passengers always take the next available seat closest to the door.”
Allocator helps you estimate how a given number of passengers would be distributed among train cars. Rather than seating the customers in a predetermined sequence, as TimeScope does, it seats them using a rule that the probability that a passenger chooses a particular train car is proportional to the desirability of that car. An example rule would be, “passengers are more likely to choose cars in the center of the train, but they don’t always.” Unlike TimeScope, Allocator does not deal with the rate at which new passengers come on board – it only specifies where a particular number would be likely to sit.
Another explanation is that Build-Out calculates “supply,” while TimeScope and Allocator calculate “demand.” TimeScope calculates demand over time using pre-set rules, while Allocator calculates demand for a snapshot in time using probabilities.
You may use decision tools in any order you wish. Following are some tips about the most common sequence of application.
If you are planning to use both Build-Out and TimeScope on the same features, it usually makes the most sense to run Build-Out before running TimeScope. After spatial build-out creates features, you can use TimeScope to look at how those features might appear over time. Note that both Build-Out and TimeScope overwrite their own previous results, so if you re-run Build-Out you will also need to re-run TimeScope.
If you are planning to use both Build-Out and Allocator on the same polygons, it usually makes the most sense to run Build-Out before running Allocator. After numeric build-out calculates the carrying capacity of each polygon, you can use Allocator to look at how much of that capacity will be used from polygon to polygon. Note that both Build-Out and Allocator overwrite their own previous results, so if you re-run Build-Out you will also need to re-run Allocator unless you have set it up to re-run automatically.
TimeScope and Allocator can be used together in many different combinations. It’s useful to remember that TimeScope works on individual features, while Allocator is usually used for “containers” such as parcels or plots. Here are some typical methods for using the two tools in conjunction:
Use the Features Built indicator generated by TimeScope as the Demand value for Allocator. This will cause the same number of features built by TimeScope to be distributed by Allocator, but they may not occur in the same places.
Use the negative of the Phasing attribute in TimeScope as a desirability Score attribute in Allocator and compare results. (One needs to be the negative, or inverse, of the other because phase attributes are used in order from lowest to highest, and scores are used in order from most desirable to least desirable.) If you use “probability-based” allocation you will see the effects of randomness.
Run an allocation on individual features, and then run TimeScope on those that have been selected.