Calculate Prediction Zones

Summary

Identify areas at risk of repeat and near repeat incidents by specifying the spatial and temporal range of influence of past incidents.

Usage

  • The Input Features must be a point feature class or shape file with a date field, representing the locations of incidents.
  • The tool will use all points with date values in the Temporal Range of Influence preceding the Initial Processing Date. Features with date values outside this range and features with null or invalid date values will not be processed.
  • This tool will honor a selected set of features. When the Input Features contain a selection, only the selected features will be considered when building the prediction zones.
  • Incidents that occur closer in time to the Initial Processing Date will have more influence over the prediction zones than older incidents. Areas nearer to incidents will be considered to have a greater risk of future incidents, up to the Spatial Range of Influence. Use the Spatial Half Distance and Temporal Half Life parameters to modify the rate of decay of influence.
  • The following fields are populated in the output feature class:
    • CREATEDATE: Text field populated with the date and time the features are created.
    • STARTDATE: The Initial Processing Date, or the calculated date if TODAY or YESTERDAY is the input value.
    • TIMEBAND: The Temporal Range of Influence used to generate the features.
    • SPACEBAND: The Spatial Range of Influence used to generate the features.
    • RISKRANGE: The classification of risk for the area defined by that polygon. Higher values have a higher level of risk ang lower values have a lower value of risk based on the location and dates of nearby incidents.
  • This tool creates up to two outputs:
    • A raster representation of the levels of risk over the area covered by the incidents.
    • Polygons generated by binning the raster values into a number of Risk Ranges are appended to the Output Prediction Zones Feature Class as described above.
  • While storing the output raster in a geodatabase is supported, it is recommended to store the raster in a folder rather than a geodatabase, especially if this tool will be run as a scheduled task.
  • All distances are calculated using geodesic measurements.
  • This tool requires the Spatial Analyst extension.

Syntax

CalculatePredictionZones_crime (Input_Features, Output_Prediction_Zones_Raster, Output_Prediction_Zones_Feature_Class, Date_Field, Initial_Processing_Date, Spatial_Range_of_Influence, Spatial_Half_Distance, Temporal_Range_of_Influence, Temporal_Half_Life, Risk_Calculation_Method, Number_of_Risk_Ranges)

Parameter Explanation Data Type
Input Features Feature class containing points representing the location of incidents and from which prediction zones will be calculated. The feature class must have a date field (in date format) and all features must have date values. Feature Layer
Point Join Features Point features coincident with the input polygon or line features. Feature Layer
Output Prediction Zones Raster Output prediction zone raster. Raster Layer
Output Prediction Zones Feature Class Output feature class with polygons representing the prediction zones. Feature Class or Feature Layer
Date Field The field in the input feature class containing the date on which each incident occurred. If the date of the incident spans a range (for example, date information is recorded in two fields representing the from and to dates), choose the date field you consider to be most appropriate. This will usually be the date at the beginning of the date range. Values in the date field are used to calculate the level of future risk based on a combination of when the incident occurred, the Initial Processing Date and the temporal decay in risk (determined from the Temporal Range of Influence and the Temporal Half Life). Field
Initial Processing Date The date to use from the Input Feature Class for creating the prediction zones. Date
Spatial Range of Influence This value determines the size of the prediction zones around each incident (in the units of the coordinate system of the Input Feature Class). The value refers to the maximum distance from an incident that the incident is estimated to have on influencing the risk of future incidents taking place. Additionally, this value can be based on the area around an incident that is considered to be practical for resource targeting and deployment (for example, the area to which additional patrols are targeted). Double
Spatial Half Distance The distance from an incident at which the risk is estimated to be half that of another incident taking place (a near-repeat). This value is used to calculate the exponential rate of decay in the spatial risk of a near-repeat incident and must be lower than the value for the Spatial Range of Influence. Distance units are the units of the coordinate system of the input feature class. A useful initial value to apply is half the value of the Spatial Range of Influence. Double
Temporal Range of Influence This value refers to the number of days before the Initial Processing Date that incidents are estimated to have an influence on the risk of future incidents taking place. More recent incidents have the greatest level of influence on future risk. Incidents that took place between the Initial Processing Date and the value for the Temporal Range of Influence are used for creating prediction zones. For example, if this value was set to 3, only incidents for the Initial Processing Date and the two days prior would be used for creating prediction zones. Incidents that took place 3 days ago would have less of an influence on the risk of future incidents than those that took place on the Initial Processing Date. Double
Temporal Half Life The number of days before the Initial Processing Date on which the risk is estimated to be half that of further incidents taking place immediately after the Initial Processing Date (for example, incidents that took place on the Initial Processing Date are considered to have the greatest influence on the risk of future incidents taking place. Incidents before the Initial Processing Date have less of an influence on future risk). This value is used to calculate the exponential rate of decay in the temporal risk of a repeat and near-repeat incident and must be lower than the value for the Temporal Range of Influence. A useful initial value to apply is half the value of the Temporal Range of Influence. Double
Risk Calculation Method

Choose the method for calculating the predictive risk.

    'CUMULATIVE' (default) creates prediction zones where the value of each cell is the sum of any prediction zone cells that overlap.
    'MAXIMUM' creates prediction zones where the value of each cell is the maximum value of any prediction zone cells that overlap
String
Number of Risk Ranges Integer value representing the number of ranges that will be used in the polygon version of the output for representing the variation in predicted risk (for example, if this value was set to 2, two Risk Ranges would determine areas of primary risk from areas of secondary risk). Long

Licensing information

  • ArcGIS Desktop Basic: Requires Spatial Analyst
  • ArcGIS Desktop Standard: Requires Spatial Analyst
  • ArcGIS Desktop Advanced: Requires Spatial Analyst
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