Spatial Disaggregate Module

The Spatial Disaggregation Module deals with disaggregating zonal information to a finer grid cell level. In its current form, this module disaggregates the zonal population and job predictions obtained from the Land Use Module to the grid cell level. It also disaggregates the link level predictions for each modeled vehicle class that are obtained from the Transportation Module to the grid cell level. The transportation predictions that are disaggregated include: traffic flows, vehicle kilometers traveled (VKT) and vehicle minutes traveled (VMT) to the grid cell level. This disaggregated land use and transportation information is primarily used as input variables to the Air Quality Module in case the user decided to employ the Land Use Regression (LUR) Modeling approach to predict air pollution concentrations.

The process of disaggregation is done based on the concordance of IDs between the Grid Cells Layer and the Zones Layer in the case of population and jobs. On the other hand, the process is done based on concordance of IDs between the Grid Cells Layer and Links Layer in the case of traffic volume, VKT, and VMT. Here, the software relies on input information provided by t he user which defines the presence of a particular land use type (e.g., residential or commercial) in the used grid cell layer. The fields storing the information are set up as categorical variables taking on the value of 1 if a particular land use type is found in the grid cell, 0 otherwise. For instance, if a field, say RESDLU is introduced to represent the residential land use, then the values in this field will be set to 1 if the grid cell intersects with residential land use, 0 otherwise. The program will assign population to the grid cells with RESDLU equal to 1 within the zone evenly.

Alternatively, the field for all the grid cells that fall within a particular zone could be setup to have weights that add up to 1 for the specific land use type. In this case, the population in the zone is distributed to the grid cells based on the provided weights. The same is done for the jobs using a field representing the non-residential land use in the grid cells. In the case of traffic flow, VKT, and VMT, the program will assign link level values to the grid cells where the links and grids intersected. For example, if a grid cell has two roads (links) going through it, then the traffic flow pertaining to the two links is added and assigned to the grid cell. The same is done for the VKT and VMT.